IMPORTANT The Abstracts contained in this Book of Abstracts are the Preliminary abstracts supplied by the authors and are only provided to assist you with choosing the presentations you wish to attend at the Symposium. Abstract Titles and/or text may have changed slightly and if so will be included with the final papers in the Symposium Proceedings. Please select the presentations you wish to attend prior to attending the symposium as the Book of Abstracts will not be provided as a handout and will only be available to view at the registration desk.
IGNSS2011 Book of Abstracts For Oral and Poster Presentations
Oral Presentations Abstracts – Tuesday 15 November, 2011 Session 1:
United Nations Programme on Global Navigation Satellite Systems Applications and International Space Weather Initiative Sharafat Gadimova Office for Outer Space Affairs/United Nations Office at Vienna/Austria Phone:431260605479; Fax: 4312606075479; email: firstname.lastname@example.org Hans Haubold Office for Outer Space Affairs/United Nations Office at Vienna/Austria Phone: 431260604949; Fax:4312606074949; email: email@example.com Earth‟s ionosphere reacts strongly to the intense X-ray and ultraviolet radiation released by the Sun during solar events. Stanford‟s Solar Center, Electrical Engineering Department developed inexpensive space weather monitors that scholars around the world can use to track changes to the Earth‟s ionosphere. Two versions of the monitors exist – a low-cost version named SID (Sudden Ionospheric Disturbances) designed to detect solar flares; and a more sensitive version named AWESOME (Atmospheric Weather Electromagnetic System of Observation, Modeling, and Education) that provides both solar and nighttime research-quality data. Through the United Nations Basic Space Science Initiative (UNBSSI), such monitors have been deployed to high schools and universities in developing nations of the world for the International Space Weather Initiative (ISWI). The monitors come preassembled, the hosts build their own antenna, and provide a computer to record the data and an internet connection to share their data with worldwide network of SIDs and AWESOMEs. These networks are advancing the understanding of the fundamental heliophysical processes that govern the Sun, Earth and heliosphere, particularly phenomena of space weather. Monitoring the fundamental processes responsible for solar-terrestrial coupling are vital to being able to understand the influence of the Sun on the near-Earth environment. A SID monitor is successfully operating at the United Nations Office at Vienna (UNOV) and will be extended to an AWESOME shortly. This project will also be supported by the programme on global navigation satellite systems (GNSS) applications, implemented through the International Committee on GNSS (ICG). ICG‟s establishment recognizes that GNSS has become a truly international resource and demonstrates the willingness by providers and users to ensure that GNSS services continue in the future for the benefit of all. KEYWORDS: ICG, GNSS, ISWI
Status of The European GNSS Programmes: Galileo and EGNOS Edgar M Thielmann European Commission, Brussels, BELGIUM
Abstract not provided
1045 - 1215
Cornerstones of a Vibrant Australian Space Industry Dr Rosalind Dubs Chair, Space Industry Innovation Council, Australia +61 2 6276 1166 (tel), +61 2 6276 1404 (fax), firstname.lastname@example.org This keynote address explores the role of the Australian Space Industry Innovation Council in advising government on the establishment of a new national space policy. With a primary focus on communications, position/navigation/timing and earth observation satellite systems, the Council aims to prioritise the space infrastructure gaps for Australia that if addressed will maximise downstream benefits to the national economy. The three application areas are compared and contrasted, with emphasis on the strategic opportunities presented by Australia‟s location, both as desirable siting for southern hemisphere ground stations servicing other nations‟ satellite systems, and as a „hotspot‟ for the several global or regional GNSS systems already in place or under development. The latter should drive a new wave of Australian-developed GNSS applications for use by a multitude of industries globally. A capacity development path for the Australian space sector going forward is also explored, from national space coordination and research support, through involvement in ground systems, hosted payloads and eventually large national projects such as the National Broadband Network space segment and a foreshadowed Synthetic Aperture Radar satellite system. A key aim for the Australian space sector is to yield over time several Australian-based multinational enterprises involved in global space industry supply chains. KEYWORDS: Space Industry Innovation Council, national priorities, infrastructure gaps, capacity development, supply chains
Australia’s National Space Policy Michele Clement Manager Space Policy Unit, Department of Innovation Industry Science and Research, Canberra, Australia
Abstract not provided
National Positioning Infrastructure – Delivering Compatible Positioning Services from GNSS Reference Station Networks Grant Hausler Cooperative Research Centre for Spatial Information, Australia Tel: (03) 9035 3223 Email: email@example.com Phil Collier Cooperative Research Centre for Spatial Information, Australia Tel: (03) 8344 8125 Email: firstname.lastname@example.org The ability to observe and distribute fit-for-purpose location information in real-time can support many activities of a modern society including; education, scientific research, business functions, government services, intelligent transport systems, location based services, national security and the maintenance of social order. Australia is aiming to develop a National Positioning Infrastructure (NPI) that will enable the determination of seamless and consistent location information on a national basis in support of a modern, spatially enabled society. In the first instance, the NPI will be based on the acquisition, processing and distribution of multi-GNSS data through a network of Continuously Operating Reference Stations (CORS). This paper begins with a revision of CORS network developments in Australia. It discusses pathways for achieving greater collaboration between public and private providers of CORS infrastructure. Emphasis is given to identifying and evaluating technical and organisational issues and thereby overcoming ad-hoc CORS network deployment and management. It is asserted that CORS market segregation has led to infrastructure over investment, variable service offerings, application specific equipment quality and capabilities, limited identification and control of quality assurance and inconsistent datum realisation – all of which can be addressed through a NPI. In response, a dedicated test framework and web-mapping platform are introduced. The Australian CORS Infrastructure (ACI) framework will support interconnection and uniform operation of existing and planned CORS infrastructure and provide a mechanism to test, communicate and promote the compatibility of CORS services nationally. KEYWORDS: Compatibility, Continuously Operating Reference Station (CORS), National Positioning Infrastructure (NPI), Global Navigation Satellite System (GNSS), Australian CORS Infrastructure (ACI)
AUSPOS2: An Update to Geoscience Australia’s Online GPS Positioning Service Minghai Jia Geoscience Australia Phone: 61262499045 email: Minghai Jia@ga.gov.au Michael Moore Geoscience Australia Phone: 61262499052 email: Michael.Moore@ga.gov.au John Dawson Geoscience Australia Phone: 61262499028 email: John.Dawson@ga.gov.au Guorong Hu Geoscience Australia Phone: 61262499884 email: Guorong.Hu@ga.gov.au AUSPOS, Geoscience Australia‟s online GPS positioning service, has now been in worldwide use since 2000 and has processed over 150,000 user data files. In 2011, the AUSPOS service was fully upgraded to use the Bernese software as the processing engine together with more sophisticated GPS data analysis strategies, new ITRF to GDA transformations and the recently developed the AUSGEIOD09 model. In this presentation, we will briefly overview the AUSPOS2 system including the improved modelling and analysis strategies employed. Then, we will present test results for AUSPOS2 using 1, 2, 6, 12, 24 hours of data from 232 IGS2008 core stations as well stations from the Asia Pacific Reference Frame (APREF) network within mainland Australia using the IGS final, rapid and ultra rapid products, respectively. Preliminary tests using 24 hours data show that coordinate differences between AUSPOS solutions and APREF weekly solutions are within millimetres for all three components.
KEYWORDS: AUSPOS2, GPS
An Infrastructure Approach to Determining the “Fitness for use” of GNSS Measurements for Land-Based Applications Steve Coleman (1) The University of Melbourne, Australia Phone & Fax No including country code plus email address Allison Kealy (2) The University of Melbourne, Australia +61 3 8344 6804 +61 3 9347 2916 email@example.com Peter Ramm The University of Melbourne, Australia +61 3 9733 0278 +61 3 9347 2916 firstname.lastname@example.org With the potential availability of several new Global Navigation Satellite System (GNSS) constellations over the next decade as well as on-going modernization of the existing GPS and GLONASS constellations, it would appear that society‟s growing dependence on GNSS will be well serviced into the future. Unfortunately, within the land domain, the increasing reliance on GNSS has not been matched with developments in approaches to define the “fitness” of GNSS measurements to deliver the outcomes of the applications they underpin. This situation is even more critical as safety guarantees and legal evidentiary needs are increasing reliant of GNSS in land based applications. Approaches to providing robust integrity information for GNSS position and speed in the land environment have lagged significantly behind the aviation and maritime sectors. For example, the land environment has no operational equivalent of RAIM (Receiver Autonomous Integrity Monitoring), and very little has been developed by way of metrics to support monitoring and assessment of integrity, for land applications. As a result, land-based GNSS users and associated regulators are currently unprepared to meet the emerging evidentiary requirements of critical applications; for example the management of heavy vehicle along defined routes or virtual tolling using GNSS. This paper explores the need to develop an appropriate infrastructure that enables users to determine whether their GNSS measurements are fit for their intended purpose. It presents a comparison of similar infrastructures implemented in the maritime and aviation environments and evaluates their applicability to the land domain. From these comparisons the components of a suitable potential infrastructure for land applications is presented. The need for the infrastructure and the applicability of the components identified will be evaluated in this paper through a case study in road vehicular transportation. The infrastructure is tested for robustness in a 'real world' heavy vehicle environment within Australia where operational GNSS devices are subjected to various forms of interference, those occurring naturally and those which can be simulated. A quantitative analysis will be performed to determine how best the integrity of measurements can be qualified by available data metrics and also by interpolation predictions based on historic baseline testing and quantification. KEYWORDS: Integrity, Infrastructure, Land Applications, Road Transportation
GNSS Modernisation and Implications for Geodesy and Precision Users Chris Rizos University of New South Wales, NSW 2052, Australia Tel: 61-2-9385-4173, Fax: 61-2-9313-7493 email: email@example.com The declaration of “Full Operational Capability” of the U.S.‟s Global Positioning System (GPS) in the mid1990s has changed geodesy and surveying irrevocably. As a result of the revolution wrought by the progressive introduction of GPS technology, positioning and navigation has increasingly become a critical technology for machine automation, emergency services, military operations, rapid mapping, transport management, car navigation systems and personal mobility. Yet the future will include many more satellitebased positioning systems, collectively known as Global Navigation Satellite Systems (GNSS), as well as many augmentation systems, and even new (non-satellite) location determination technologies. Over the next 5 or so years there will be a surge of new navigation satellite systems launched, with an expected quadrupling of satellites and signals. This “next generation GNSS” will collectively include the U.S.‟s modernised GPS and planned GPS-III constellations, Russia‟s GLONASS, Europe‟s GALILEO system, and China‟s BEIDOU system. Within the international community, e.g. through discussions within the U.N.‟s International Committee on GNSS (ICG), the focus is on a “multi-GNSS” world where interoperability and compatibility are aspirational goals. The ICG is a forum for both the signal providers as well as NGOs representing different classes of users (including surveyors, geodesists, marine and aviation navigators,
etc.). However, the precise positioning users require special attention. Precise positioning for geodetic, surveying and critical real-time machine guidance applications requires a substantial investment in ground infrastructure in the form of continuously operating reference stations (CORS) and associated ICT components. Governments (federal and state/provincial/local) around the world are currently establishing CORS networks to address several precise positioning „markets‟. This presentation provides an overview of “where we‟re at”, and explores some of the implications of next generation GNSS from the perspective of precise positioning. In particular, issues such as heirarchical “tiers” of CORS, unification of national and international CORS infrastructure, the role of the IGS, capabilities of the next generation CORS receivers, and deployment strategies for future CORS will be discussed. KEYWORDS:GNSS, geodesy, IGS, geodetic infrastructure.
The Australian Space Research Program Project - Platform Technologies for Space Atmosphere and Climate Kefei Zhang, Robert Norman, Chuan-sheng Wang, Brett Carter and Ming Zhu Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, RMIT University of Melbourne, GPO Box 2476V, Melbourne Australia Peter Teunissen and Dennis Odijk Dept of Spatial Sciences, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia Chris Rizos and Samsung Lim School of Surveying & Spatial Information Systems, University of New South Wales, Sydney NSW Australia Jizhang Sang Electro Optic Systems Space Systems Pty Ltd, 111 Canberra Ave, Griffith, ACT, Australia Yuei-An Liou Center for Space and Remote Sensing Research, National Central University, No.300, Jhongda Rd, Jhongli City, Taoyuan, Taiwan 32001, Republic of China John Le Marshall and Yuriy Kuleshov Bureau of Meteorology, GPO Box 1289, Melbourne VIC, Australia Graeme Hooper GPSat Systems Australia Pty Ltd, 22 Aberdeen Rd, Macleod VIC, Australia This contribution will first introduce the multi-million dollar Australian Space Research Program Project – “Platform Technologies for Space Atmosphere and Climate” as part of the Australian Government's recent space-related initiatives to support national strategic, economic and social objectives. The research consortium consists of RMIT University (leading), the Bureau of Meteorology, Curtin University of Technology, the University of NSW, Electro Optic Systems Space System, GPSat Systems Australia and National Central University of Taiwan in conjunction with National Space Organisation Taiwan and NOAA‟s World Data Centre for Meteorology. This aims and objectives, primary research tasks and work packages of the project and anticipated outcomes will be outlined. Key issues related to the research work and challenges confronting Australian space research and space industry will be discussed, particular those research tasks in the context of new generation GNSS and its innovative applications in space weather, space tracking, climate and positioning, navigation and timing (PNT). Major preliminary findings and results in the areas of PNT, space geodesy-based atmosphere sounding, climate change, space weather and environment will be presented. Finally, our view on future space research related to GNSS and space geodesy which is a key component of the ever-expanding future earth observation systems will be given.
Ionosphere / Troposphere
Analyzing Zenith Path Delay in Dynamically Changing Environment Mukesh R. Vyas, Samsung Lim, Chris Rizos School of Surveying and Spatial Information Systems, The University of New South Wales. Tel: - +61-2-9385 4205 Fax: - +61-2-9313 7493 Email: - firstname.lastname@example.org Website: - www.gmat.unsw.edu.au Kefei Zhang School of Mathematical and Geospatial Sciences, The RMIT University . Gregor Moeller Insitute of Geodesy & Geophysics, Technical University of Austria. Many studies have been conducted for evaluating the tropospheric effect on GPS signals because it is well known that GPS signals are delayed due to various atmospheric conditions. From many troposphere models, the Saastamoinen model and the Neill model have been widely used. That is, the troposphere‟s zenith path delay can be obtained by the hydrostatic component of the Saastamoinen model and then the delay can be mapped with the dry Niell mapping function in order to obtain the slant path delay. This paper aims to identify and analyse the pattern of the tropospheric delay in an aircraft‟s flight trajectory using the aforementioned troposphere models. The test data set includes the kinematic data observed during a 700km-long flight at the maximum ellipsoidal elevation of 3,300m and the static data observed at seven reference stations distributed across the study area. The data was processed on an epoch-by-epoch basis in the double-differenced mode with mixed, kinematic and static stations. The correlation between the delay and the flight height is addressed as a result of the analysis. Since the delay estimation can be affected by the data quality, the baseline length and other factors, it is necessary to cross-verify the estimation; hence the correlation between the delay and its expected accuracy is assessed along the flight trajectory. KEYWORDS: Troposphere effect, Zenith Path Delay, Slant Path Delay, Saastamoinen model, Neill model.
Consideration of RTZD Estimated from Ground Reference Stations for GNSS Application Joz Wu (1) Center for Space and Remote Sensing Research/National Central University/Taiwan 886-3-422-9332#57626 email@example.com Yang-Zen Chen (2) Department of Civil Engineering/National Central University/Taiwan 886-3-422-9332#57615 firstname.lastname@example.org Global navigation satellite systems have been successfully applicable. But in the process of positioning, there are many errors which affect the accuracy of positioning. The ionosphere and troposphere delays are the largest error sources. And they cannot be eliminated by a double difference technique. When processing code- and carrier-phase ranges sampled at individual epochs by a pair of reference receivers on the ground where the positions are known, the control baseline can produce relative integer ambiguities and delay estimations. The estimates are very accurate with the formal errors lying within bounds, and they could function as constraints, when a roving user who operates in the network of reference sites requires instantaneous position solutions. In this research, the user‟s positioning accuracy is improved by using a tropospheric zenith delay surface which is produced by interpolating the estimates of network references. It is also explained how a system of error equations for real measurements is stacked up with another system of pseudo-observations for parametric constraints before least-squares adjustment is routinely carried out. A local network of several reference stations was experimented to study single-epoch position estimation. This estimation reveals that with the increased reliability of ambiguity resolution on both L1 and L2 carriers, GPS-derived height accuracy is expected to be refined further. KEYWORDS: Single-epoch GPS ranging, Ionosphere, Troposphere, Ambiguity resolution, Positioning accuracy.
Performance Evaluation of Single Frequency-based Ionosphere Field Monitor for GBAS Seigo Fujita Electronic Navigation Research Institute 7-42-23 Jindaijihigashi-machi, Chofu, Tokyo 182-0012, Japan Tel: +81-422-41-3191, Fax: +81-422-41-3199, E-mail: email@example.com Takayuki Yoshihara Electronic Navigation Research Institute 7-42-23 Jindaijihigashi-machi, Chofu, Tokyo 182-0012, Japan Tel: +81-422-41-3181, Fax: +81-422-41-3199, E-mail: firstname.lastname@example.org Susumu Saito Electronic Navigation Research Institute 7-42-23 Jindaijihigashi-machi, Chofu, Tokyo 182-0012, Japan Tel: +81-422-41-3191, Fax: +81-422-41-3199, E-mail: email@example.com In this paper, we evaluate a performance of an anomalous ionospheric gradient detection algorithm by using observed ionospheric data in short baseline occasions of a few kilometers. It is recognized that large ionospheric spatial gradients could result in significant positioning error, therefore large ionospheric gradients are regarded as a potentially threatening error source for the Ground Based Augmentation Systems (GBAS). Electronic Navigation Research Institute (ENRI) has developed a CAT-I GBAS prototype and installed it at Kansai International Airport in November 2010. The prototype includes an additional ground monitoring station as an Ionospheric Field Monitor (IFM), which is designed to detect anomalous ionospheric gradient. We have proposed a single frequency-based anomalous ionospheric gradient detection algorithm for the IFM to mitigate the potentially threatening error source due to anomalous ionospheric gradients. The IFM is able to accurately detect anomalous ionospheric gradients within a distance of several kilometers by applying the Kalman filter to the Single Difference (SD) measurement model with carrier phase and pseudorange measurements. The IFM is designed to detect anomalous ionospheric gradients that are assumed to be proportional to the distance from GBAS reference stations. Our proposed algorithm for the IFM has also a potential to detect ionospheric anomaly gradients with shorter baseline occasions such as a baseline between the GBAS reference stations. Ionospheric gradient detection between reference stations is indeed required for next generation GBAS supporting lower runway visibility conditions. The purpose of this study is to evaluate the relationship of the detection sensitivity and several baseline occasions between two monitoring stations by using observed anomalous ionospheric data in short baseline occasions. Finally, we show experimental results in several short baseline occasions, and clarify detection sensitivity limitation with each baseline distance between two monitoring stations. KEYWORDS: Ionosphere Field Monitor (IFM), Anomalous Ionospheric gradient, Ground Based Augmentation Systems (GBAS)
Recent Developments In Regional Ionospheric Modelling And Monitoring For GNSS Applications Dr Zahra Bouya Dr Michael Terkildsen Dr Matthew Francis IPS Radio and Space Services Australian Bureau of Meteorology +61 (2) 9213 8000 IPS Radio and Space Services, within the Bureau of Meteorology is Australiaâ€&#x;s space weather agency providing services in the fields of HF communications, geophysics, satellite operations and GNSS. We will present details of our currently available GNSS services including ionospheric scintillation monitoring and total electron content (TEC) real time maps, including single frequency ionospheric positioning error maps. GNSS relevant services in development will also be presented including TEC forecasting, and TEC gradient warnings for GBAS and RTK applications. KEYWORDS: Ionosphere, Total Electron Content, space weather, scintillation, services
Weak Signals / AGNSS
1315 - 1455
Efficient Implementation of Collective Detection Joon Wayn Cheong School of Surveying and Spatial Information Systems, University of New South Wales/Australia +61 2 93854206/ firstname.lastname@example.org Jinghui Wu School of Surveying and Spatial Information Systems, University of New South Wales/Australia +61 2 93854206/ email@example.com Andrew G. Dempster School of Surveying and Spatial Information Systems, University of New South Wales/Australia +61 2 93856890/ firstname.lastname@example.org Chris Rizos School of Surveying and Spatial Information Systems, University of New South Wales/Australia +61 2 93854205/ email@example.com Collective Detection is a position domain detection algorithm that combines simultaneous signals from multiple satellites onto a geographical search space for acquisition, and provides a position estimate as a byproduct of the Maximum Likelihood detection process. This results in increased peak-to-noise ratio in the combined cost function and has been proposed in recent years to increase detection sensitivity. Collective Detection exploits the small receiver uncertainty area and accurate satellite ephemeris data provided by AGPS servers via nearby WiFi or cellular networks. Many previous researchers investigated the accuracy of the Collective Detection concept by assuming perfect a priori knowledge of the true receiver common-bias and positions of all satellites in-view. At the very least, the common-bias is assumed to be restricted to a small uncertainty range so that implementation is feasible for experimentation. This is typically not the case, especially in cold or warm start scenarios where the receiver trigger time for snapshot data collection is uncertain. This paper proposes an efficient implementation to search the entire common-bias domain by restricting the common-bias grid spacing to be an integer multiple of its sampling period. To further allow Collective Detection to be performed for low-memory computer systems, a multi-resolution search is proposed. Through a multi-resolution search, the search is split into several iterations, with each iteration having a smaller grid spacing than the previous iteration. In this way it searches the entire receiver uncertainty area and achieves similar search resolution without evaluating all grid points. This paper also discusses the implementation of Collective Detection in a Master (MS) â€“ Rover scenario, which allows the elimination of various errors due to atmospheric effects. KEYWORDS: Collective Detection, Common Bias, A-GPS, Signal Processing
Hybrid of Collective Detection with Conventional Detection for Weak Acquisition Joon Wayn Cheong School of Surveying and Spatial Information at the University of New South Wales/Australia +61 2 93854206/ firstname.lastname@example.org Andrew G. Dempster School of Surveying and Spatial Information at the University of New South Wales/Australia +61 2 93856890/ email@example.com Chris Rizos School of Surveying and Spatial Information at the University of New South Wales/Australia +61 2 93854205/ firstname.lastname@example.org Recently, the method of Collective Detection has been applied in the case of GPS L1 signal acquisition as a proof-of-concept. However, under practical scenarios, there are typically only up to 8 satellites in view simultaneously (assuming a 15 degree mask angle). The limited availability of simultaneous GPS L1 signals leads to the consideration of combining more signals from GPS L2C, L5, Galileo E1, etc. In addition, many previous techniques have avoided the issue of unequal C/No, which is typical of a challenging GNSS environment (e.g. urban canyons). In this paper a simulated dual-constellation scenario is examined where there are few (fewer than three) strong signals from one constellation (e.g. via the use of synchronised LocataLites) and a number of weak
signals from the conventional GPS L1 constellation. Where individual GPS L1 signals are too weak to be detected, conventional detection and navigation methods will not be able to yield sufficient pseudoranges to produce navigation solutions. In this scenario Collective Detection, which combines individual GPS L1 signals onto a position domain, collectively forms a strong peak at the correct position. However this direct method neglects the strong signal received from the alternate constellation. To utilise the detected strong signals (via conventional detection), the measured pseudoranges can be used to reduce the solution space for Collective Detection. It is well known that one dimension in the solution space can be eliminated for each pseudorange found. This paper details a hybrid method that can be used to reduce the search space of Collective Detection such that a better position solution and lower computation load can be achieved. These methods can also be applied in scenarios where the received signals have unequal C/No, provided that the strong signals can be detected using conventional detection methods. KEYWORDS: Collective Detection, Signal Processing, Hybrid Acquisition, Locata
Sensitivity Analysis of Assisted-Galileo Receiver with E1 OS Signal Jeong-Min Lim Department of Information and communication Engineering Chungnam National University, Korea Tel:+82-42-821-6807, Fax:+82-42-824-6807, email@example.com Ji-Won Park Department of Information and communication Engineering Chungnam National University, Korea Tel:+82-42-821-6807, Fax:+82-42-824-6807, firstname.lastname@example.org Tae- Kyung Sung Division of Electric and Computer Engineering Chungnam National University, Korea Tel:+82-42-821-5660, Fax:+82-42-824-6807, email@example.com The European GNSS system â€œGalileoâ€? uses three frequency bands and provides five kinds of services. The receiver manufacturer are trying to utilize Galileo open service(OS) signals in order to improve their receiver performance. Because GPS L1 and Galileo E1 band have same center frequency, Galileo E1 OS uses Composite-BOC(CBOC) modulation techniques in data and pilot channel to guarantee low interference between GPS L1 civil signals and E1 OS signals. In many LBS applications, assisted GNSS technique is required to provide fast TTFF and high sensitivity. In order to develop assisted GNSS receivers integrating GPS and Galileo system, the sensitivitiy analysis for Galileo E1 OS signal as well as for GPS civil signals should be considered. This paper proposes Galileo SNR and it is verified by computer simulation. In case of Galileo E1 OS signal worksheet, the signal bandwidth and implementation losses are different from those of GPS. SNR worksheets for Data channel E1-B and pilot channel E1-C of Galileo E1 OS are derived respectively and their performances are compared. If the signal strength, sampling frequency and hybrid integration time are given by -150dBm, 32.768MHz and 1.5s, computer simulation shows that E1-B channel can achieve final SNR of 26.5dB using 4ms coherent and 375 times non-coherent integration, E1-C channel accomplish final SNR of 32.2dB by 1.5s hybrid integration using 100ms coherent and 15 times non-coherent integration. KEYWORDS: SNR Worksheet, Galileo E1 OS
How good is Assisted GPS? Binghao Li University of New South Wales, Sydney, Australia 02-93854189 & 02-93137493 firstname.lastname@example.org Jiahuang Zhang University of New South Wales, Sydney, Australia Peter Mumford University of New South Wales, Sydney, Australia 02-93854189 & 02-93137493 email@example.com Andrew G. Dempster University of New South Wales, Sydney, Australia Assisted GPS (A-GPS) is being increasingly recognised by the public, users expecting to have a better performance of the A-GPS enabled devices than the conventional GPS receivers. This paper reported the
evaluation of several A-GPS enabled receivers using a GPS signal generator and a specifically developed software. Under ideal conditions, several different scenarios were created to test the devices. Time To First Fix (TTFF) and positioning accuracy were the two aspects of most interest. The results show that these AGPS enabled receivers can obtain reasonable position solutions in well under 30 seconds, especially the newer receivers which have TTFF typically less than 10 seconds, can be as low as 3 seconds. Better performance of the new receivers in the market is expected. KEYWORDS: Assisted GPS, Time To First Fix, positioning accuracy
Proposing a Multi-GNSS Assisted GNSS (Global Navigation Satellite System), Concept and Performance Ali Sarwar School of Surveying and Spatial information Systems, UNSW, Australia Phone : +61 2 9385 4185, Fax : +61 2 9313 7493 Email: firstname.lastname@example.org Eamonn Glennon School of Surveying and Spatial information Systems, UNSW, Australia Phone : +61 2 2 93137493, Fax : +61 2 9313 7493 Email email@example.com Chris Rizos School of Surveying and Spatial information Systems, UNSW, Australia Phone: +61 2 9385 4205, Fax: +61 2 9313 7493, Email: firstname.lastname@example.org Open Source GNSS Reference Server (OSGRS) exploits the GNSS Reference Interface Protocol (GRIP) and was first specified to provide Assistance to Global Positioning and Navigation Systems. Assistance types can be both in acquisition and processing data. Data transfer protocol is based on Extensible Mark-up Language (XML) schema. Its java based software architecture allows flexible new software module integration. The first version required a hardware connected GPS source to acquire and store assistance data on request-response based provisioning. Scenarios of interest are obviously weak signal strength indoors, unclear outdoors and multipath. This paper presents a subsequent improvised version of OSGRS which provides alternative assistance support from a wide array of Global Navigation Satellite Systems (GNSS). The underlying protocol to transfer GNSS assistance data from global casters is Networked Transport of RTCM (Radio Technical Commission for Maritime Services) and/or RINEX (Receiver Independent Exchange Format) over Internet Protocol (NTRIP). This expands the assistance and support model of OSGRS to globally available GNSS data servers connected through the internet caster. A vast variety of formats and versions of RINEX and RTCM streams becomes available in addition to Novatel OEM3/4 GPS source. These together strengthen the assistance provisioning capability of the platform. First integration tests are presented with previous and present assistance parameter portfolio comparison. Java code has been modified to provision this functionality both on server and client side. On server side main libraries to change are Data source managers (DRM) for GNSS Request Parser, Response Writer, Request Manager, Response Manager, Data Cache and Error Response Writer. On client side main libraries expanded are Graphical User Interface (GUI), data sourcing methodologies, html parsing routines and data retrieval functions. New routines like Ntrip Poller and Stop Crash are implemented with null checkers to support new Data Source Connectors. System configuration files have been modified to adapt to new features of data logging, retrieval and schema parsing. Old and new Code comparison reflects code changes line by line for all classes, quantification of changes and code tracking. GNSS source flexibility, higher availability, low time to fix first TTFF and higher sensitivity are some of the advantages for location based and assisted GNSS applications. This can be a cost-efficient solution requiring minimal commercial or research investment required for pre-deployment testing. KEYWORDS: OSGRS, Multi-GNSS, AGNSS, NTRIP, RINEX/RTCM
Attitude / Formation Flying
1315 - 1455
Carrier Phase Integer Ambiguity Resolution for GNSS-based Attitude Determination Chen-Yin Wang (1) Center for Space and Remote Sensing Research/National Central University/Taiwan 886-3-4227151#57615 email@example.com Joz Wu (2) Center for Space and Remote Sensing Research/National Central University/Taiwan 886-3-4227151#57626 firstname.lastname@example.org Global Navigation Satellite System (GNSS) now plays an important role in positioning and navigation. Carrier phase ambiguity resolution is the key for many applications, especially in precise and real-time GNSS-based attitude determination, because the results from carrier phase can reach centimetre or millimetre level accuracy. Therefore, finding the resolution of integer ambiguity becomes a significant task. Meanwhile, we have to ensure the quality of the answer and computational efficiency. This paper proposes several methods to guarantee the resolution quality and the computational efficiency. By double differencing the code and carrier phase observation, the GNSS baseline model, the basic equation in our experiment, is formed. The resolutions are based on a least-squares method. Decorrelation methods and simultaneous constraints are used to reduce the integer ambiguity search space; statistical tests are used to check answer correctness. The experiments include simulation and static test. The robustness and feasibility are put to the test. Experiment results are shown in the final part. It shows that our software can be modified for different applications. In our future work, we want to reach two goals: first, testing our method in dynamic situation; second, fitting our software for a challenging situation of GNSS cases, which is single frequency and single epoch attitude determination. KEYWORDS: Attitude determination, Integer ambiguity resolution, GNSS.
Simulations Platform for Relative Navigation Using GPS Carrier Phase Measurements for Satellite Formation Flying Missions Rui Li School of Information and Electronics, Beijing Institute of Technology, China School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: 61-406888160, Fax: 61-2-93137493, Email: email@example.com Yuanyuan Jiao Dept. of Mathematics and Systems Science, National University of Defense Technology, China School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: 61-4-05279093, Fax: 61-2-93137493, Email: firstname.lastname@example.org Yong Li School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: 61-2-93854173, Fax: 61-2-93137493, Email: email@example.com Chris Rizos School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: +61-2-93854205, Fax: +61-2-93137493, Email: firstname.lastname@example.org The use of Global Positioning System (GPS) technology for satellite formation flying missions has received more attention recently. The Carrier Phase Differential Global Positioning System (CDGPS) technique is generally employed to obtain relative position of a high accuracy. To validate the formation flying CDGPS algorithm, a simulation platform is necessary to simulate the GPS signals received by spaceborne receivers. This paper describes the simulation model of GPS observations for Low-Earth Orbit (LEO) spacecraft. The differences in the error sources between GPS use in space and on the ground are analysed in detail. The ionospheric effects have been identified as the main error source in space applications, especially for long baseline scenarios. Therefore the ionospheric delay model is the focus in the design of the simulation platform. Based on the platform, relative positions between two LEO satellites are derived using the L1-only and the L1/L2 carrier phase measurements. Positioning accuracy is compared with the corresponding accuracy obtained by the hardware simulator. The results show that the simulation platform is suitable for the validation of relative position determination algorithms for spacecraft formation flying missions. The modulated design and flexible parameter initialisation make the platform easily augmented for other GNSS
constellations, including Galileo, GLONASS, and Beidou. KEYWORDS: Formation flying mission, CDGPS, Simulation, Relative positioning, LEO spacecraft
Design and Analysis of Satellite Orbits for the Garada Mission Li Qiao School of Surveying and Spatial Information Systems, University of New South Wales, Australia 61(2)93856705 & 61(2)93137493 email@example.com Chris Rizos School of Surveying and Spatial Information Systems, University of New South Wales, Australia 61(2)93854205 & 61(2)93137493 firstname.lastname@example.org Andrew Dempster School of Surveying and Spatial Information Systems, University of New South Wales, Australia 61(2)93856890 & 61(2)93137493 email@example.com The Australia Centre for Space Engineering Research (ACSER) is presently investigating the design of an earth observation Synthetic Aperture Radar (SAR) satellite mission known as “Garada”, for flood monitoring and other applications using several small satellites flying in formation. In the initial feasibility study phase, satellite orbit design and analysis is one of the challenges. This paper describes the objectives of the mission and the methods that can be employed for orbit design. The main parameters determining the orbit relate to accessibility revisit requirements and mission lifetime. The requirements and considerations regarding the choice of orbit types and orbital elements for formation configuration designs are presented. Two satellites are the minimum formation; a leading satellite and a following satellite. The satellites fly in approximately 600km altitude circular orbits. Sun-synchronous and more equatorially inclined orbits are compared. The effect of altitude and satellite ballistic coefficient on orbit lifetime is analysed. The two satellites fly in a “string of pearls” formation (i.e. in line) with a separation of around 10km. The satellites use onboard GPS receivers for navigation. Predictions of GPS signal coverage on orbit are presented. Orbit lifetime, revisit frequencies, illumination time and GPS signal coverage are simulated using the Satellite Tool Kit (STK). KEYWORDS: Small Satellite, Orbit design, Lifetime，Coverage analysis, Synthetic Aperture Radar (SAR)
Datums & Geodesy
1525 - 1705
The Many Paths To A Common Ground: A Comparison Of Transformations Between GDA94 And ITRF Joel Haasdyk Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services, Bathurst NSW 2795, Australia (ph)+61 2 6332 8485, (fax)+61 2 6332 8479, Joel.Haasdyk@lpi.nsw.gov.au Volker Janssen Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services, Bathurst NSW 2795, Australia (ph)+61 2 6332 8426, (fax)+61 2 6332 8479, Volker.Janssen@lpi.nsw.gov.au Digital positioning data is currently collected and stored in a variety of reference frames or datums. Before different data can be compared or combined, they must be brought together onto the same datum. The practice of transforming from one datum to another is certainly not difficult and the necessary parameters are available in many different software packages. To complicate this issue, today‟s datum of choice may well be a global, and therefore dynamic, datum such as the International Terrestrial Reference Frame (ITRF). In a dynamic datum it is important to note the epoch at which the data are valid, and to be able to propagate the data from one epoch to another, if desired, by taking tectonic motion into account. Since the Geocentric Datum of Australia (GDA94) was introduced there have been several refinements of the ITRF, and „transformation parameters‟ are available to transform between each in turn. As a result, there are many different combinations of transformation and propagation routines by which the data can travel from GDA94 to a particular ITRF and vice versa. This paper demonstrates that differences up to several centimetres in both horizontal and vertical
coordinates can result from following different „paths of transformation‟ and suggests that some but not all users need to be careful of the methods employed by their software. Additionally, what is often not considered is the effect of the formal errors in the transformation procedure on the estimated error of the output coordinates. We discuss and demonstrate these effects for several sample transformations to give the reader a better understanding of the effect of transformations on the quality of their data. KEYWORDS: Coordinate transformation, tectonic motion, GDA94, ITRF, error propagation.
Enhancement of the Asia Pacific Reference Frame (APREF) through accurate metadata maintenance and time series offset Detection Manoj Nilesh Deo Geoscience Australia, Australia Phone: +61 2 6249 9031 Fax: +61 2 62499929 email: Manoj.Deo@ga.gov.au John Dawson Geoscience Australia, Australia Phone: +61 2 6249 9028 Fax: +61 2 62499929 email: John.Dawson@ga.gov.au The Asia Pacific Reference Frame (APREF) consists of continuously refined precise coordinate and velocity estimates of a dense network of continuous GNSS stations from the Asia Pacific region. Currently, the network includes 300 stations and continues to grow. The data from APREF stations is routinely analysed by Geoscience Australia (GA) and other Local Analysis Centres (LAC) to produce weekly coordinate solutions expressed in SINEX format. The weekly solutions from individual LAC‟s are combined at GA to form the final APREF solution. This gives users access to an improved regional reference frame through accurate and continuously refined station coordinates and velocities. One factor which limits the overall precision of APREF is the presence of undetected offsets in the time series of station coordinates. These offsets are mainly caused by equipment changes or earthquakes, at or nearby the station. If left uncleansed, these offsets will increase the uncertainty of the coordinate and velocity estimates in the APREF solution as well as the overall WRMS of the combined solution. This research utilises metadata from GA‟s centralised metadata store containing the history of the equipment changes which have taken place at all GNSS stations; such as antenna or receiver swaps, firmware upgrades and removal/ alteration of antenna domes and cables. Several change detection algorithms have been implemented for automatic detection of discontinuities in the coordinate time series. Once offsets are detected, their position in time is correlated with equipment changes or earthquake occurrences nearby the station. If a correlation is found and the offset is visibly evident, the offset is introduced into a database. This information is used in the routine combination of weekly SINEX solutions using the CATREF software to produce an enhanced set of coordinates and velocities. It is shown that after cleansing the offsets in time series using this approach, the quality of the combined APREF solution is improved in terms of WRMS. By analysing time series coordinates at a few stations using CATS software, it is shown that the uncertainty of velocity estimates is improved after offsets are detected and removed from the time series.
KEYWORDS: GPS time series analysis, offset detection, combination.
ITRF Transformations in Deforming Zones to Support CORS-NRTK Applications Richard Stanaway School of Surveying and Spatial Information Systems, University of New South Wales, Australia +61 3 9486 7845 richard.stanaway@student,unsw.edu.au Craig Roberts School of Surveying and Spatial Information Systems, University of New South Wales, Australia +61 2 9385 4464 firstname.lastname@example.org NRTK requires precise coordinates of the parent CORS network in order to operate effectively. Typically, an ITRF aligned reference frame is used as the datum for a CORS network as this enables IGS orbit products to be used without further transformation. But fixing the coordinates of the CORS network at an arbitrary reference epoch of ITRF is not feasible if the CORS network is deforming as a result of plate tectonics, ground subsidence or uplift. The effect of internal deformation can be overcome by using a fully kinematic ITRF realisation of the network. For most users however, kinematic coordinates present significant practical issues particularly with regard to integration of spatial data collected at different epochs and coordinate repeatability within a localised reference frame. This paper describes a methodology that can be utilised within deforming zones to enable kinematic ITRF coordinates of a deforming CORS network to be transformed to a fixed reference epoch without significant loss of precision. The methodology can also be applied to rigid networks on rapidly rotating tectonic plates or microplates. Adoption of this strategy allows kinematic ITRF to be used for CORS integrity monitoring whilst users of the system (e.g. surveyors and precision navigation applications such as controlled traffic steering in agriculture and automated mining) are not encumbered with the complexity of a kinematic reference frame.
KEYWORDS: CORS, NRTK, ITRF, Kinematic Datum
Establishing a Horizontal Velocity Model of Taiwan Using GPS Observations and the Least-squares Collocation Technique Ching-Jung Hung Department of Geomatics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2370876 ext. 832 / email address: P66984100@gmail.com Ming Yang Department of Geomatics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2757575 ext. 63820 / email address: email@example.com Taiwan is located at the boundary between the Eurasia plate and Philippines sea plate, where active plate motion leads to significant annual displacements of geodetic control points up to 4-5 cm. For the purpose of maintaining the existing Taiwan Geodetic Datum 1997 (TWD97) horizontal coordinate system which is connected to the International Terrestrial Reference Frame (ITRF), this research aims at predicting the yearly displacements of thousands of control points of various orders by establishing a horizontal velocity model of Taiwan. This velocity model is composed of two groups of physical parameters which characterize the regional block motions and the residual systematic signals, respectively. We used GPS-derived velocity observations collected at 426 points from 1993 to 2005 and the Least-squares Collocation (LSC) technique to create this model. And for validating the model, we further adopted 24 evenly distribute continuous GPS tracking stations as external check points. The overall precision of validation is Âą7.04 mm/yr in the E-W direction and Âą4.63 mm/yr in the N-S direction. The results show that the developed model is capable of providing accurate estimates of annual displacements of geodetic control points in Taiwan. KEYWORDS: International Terrestrial Reference Frame, Geodetic Control, Horizontal Velocity Model, Leastsquares Collocation
A Combination Of Ellipsoidal Height From Satellite Method And Orthometric Height For Geoid Modelling Kamorudeen F. Aleem Department of Geomatics Engineering, Yanbu Industrial College, Yanbu Industrial City, Saudi Arabia Surveying and Geoinformatics Programme, Abubakar Tafawa Balewa University, Bauchi Nigeria +966531259497 e-mail: firstname.lastname@example.org OR email@example.com J. B. Olaleye Department of Surveying and Geoinformatics, University of Lagos, Nigeria +2347087682900 e-mail: firstname.lastname@example.org O. T. Badejo Department of Surveying and Geoinformatics, University of Lagos, Nigeria +2348038636448 e-mail: email@example.com J. O. Olusina Department of Surveying and Geoinformatics, University of Lagos, Nigeria +2348050483736 e-mail: firstname.lastname@example.org The geoid is that equipotential surface which would coincide exactly with the mean ocean surface of the Earth, if the oceans were in equilibrium, at and extended through the continents. The geoid surface is irregular, but considerably smoother than Earth's physical surface. Sea level, if undisturbed by tides, currents and weather, would assume a surface equal to the geoid. Determination of the geoid has been one of major challenges of geodesists. Gravity data have been used in the past with stokes integration and least squares collocation for determining the geoid. This method is expensive and laborious. Geoid determination using integration of data from geodetic levelling and GNSS are taking over from geoid determination using gravity data. Data from Global Navigation Satellite System reduces the time, cost and energy in geoid modelling. This is to make the conversion of WGS‟84 ellipsoidal heights to orthometric height, easier than the existing methods. In this work, the geoid for Port-Harcourt Area in Nigeria was modelled using combined orthometric height from geodetic levelling with ellipsoidal height from Differential Global Positioning System. The acquired data were used to develop polynomial models using Least squares method. Statistical test and analyses such as the goodness of fit of the data were carried out. The model was also validated using some of the acquired data that were not used for the development of the model. The results of the models compared favourably with some of the existing methods. The method for geoid determination in PortHarcourt area can be generally extended to other parts of the world and to other parts of Nigeria in particular.. KEYWORDS: Geoid, Modelling, Ellipsoidal height, Orthometric height, „satlevel‟
Other Locations Systems
1525 - 1705
Visual Odometry and Inertial-SLAM Integration for Large Scale Navigation Usman Qayyum School of Engineering, Australian National University Canberra, ACT 0200, Australia email@example.com Jonghyuk Kim School of Engineering, Australian National University Canberra, ACT 0200, Australia firstname.lastname@example.org This paper addresses the theoretical and experimental development of an inertial-visual navigation approach seamlessly integrating visual odometry and inertial-SLAM to provide aid for inertial systems. One of key challenges towards a lightweight low-cost inertial and vision system is reliable and constant aiding to correct the intrinsically unstable inertial system. The key contribution of this work is to consider the scale-ambiguous translation from the visual odometry as a directional constraint (DC) to the vehicle motion, and thus avoiding the scale problem whilst reducing the tangential error of the vehicle motion. To further constrain the unobservable longitudinal error, inertial-SLAM framework is incorporated. Simulation and outdoor experiment results will be provided which shows the improved and consistent navigation and mapping performances compared to existing feature-based inertial-SLAM approaches. KEYWORDS: Inertial Measurement Unit, Visual Odometry, Visual Directional Constraint, Simultaneous localisation and mapping
Performance of mobile WiMAX geo-location using simplified multipath mitigation method in dense multipath environment Ji-won Park (1) Department of Information and Communication Engineering Chungnam National University, Korea Tel: +82-42-821-7607, Fax: +82-42-824-6807, email@example.com Jeong-Min Lim (2) Department of Information and Communication Engineering Chungnam National University, Korea Tel: +82-42-821-7607, Fax: +82-42-824-6807, firstname.lastname@example.org Tae-Kyung Sung (3) Division of Electric and Computer Engineering Chungnam National University, Korea Tel: +82-42-821-5660, Fax: +82-42-824-6807, email@example.com Geo-location can be performed in mobile WiMAX system by using various methods; Cell-ID, RSSI (radio signal strength index), or multilateration method. Considering the accuracy and consistency in positioning error, multilateration method is generally preferred in many geo-location applications. To perform successful geo-location using multilateration method, sufficient number of range measurements should be obtained at the receiver. Moreover, increased number of range measurements generally enhances the geo-location performance. Thus, it is profitable to detect RAS (radio access station) as many as possible. However, it is hard to detect signals of neighbor RASs in most of area due to near-far effect induced by CCI (co-channel interference). If multipath signals exist in real environment, the direct and non-direct multipath component will cause additional near-far effect. Additionally, it may be occurred that non-direct multipath component is detected as the first arrival signal, causing range measurement error. Therefore, in multipath environment, multipath mitigation should be considered together with the CCI cancelation. Interference cancelation method can be used to mitigate CCI effect. In this paper, multipath mitigation method is used together with the interference cancelation. For this purpose, repetitive structured interference cancellation with simplified ML (maximum likelihood) is used. By using the proposed multipath mitigation method, number of detected RAS will increase and the ranging measurement accuracy will be increased by detecting the true first arrival signal. In conclusion, the overall geo-location performance in mobile WiMAX system will be enhanced when the proposed method is employed. KEYWORDS: Multipath mitigation, Multilateration, mobile WiMAX, OFDMA
A Relative Navigation Scheme Using the AIS Datalink Young Hoon Han (1) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Sung Lyong Cho (2) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Heon Ho Choi (3) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Chansik Park (4) Department of Electronics Engineering/Chungbuk National University/Korea email@example.com Sang Jeong Lee (5) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org The AIS(Automatic Identification System) is a two-way maritime safety communication system between a vessel and a vessel, a vessel and a control center in the VTS(Vessel Traffic System) to enhance maritime safety. The vessels equipped AIS gets a vessel position using the GNSS receiver, and broadcasts the position, speed, course and other information using the VHF channels with SOTDMA(Self Organized Time Division Multiple Access) protocol. Since the GNSS signal power is very low, it is vulnerable to many environmental facts. In case of the GNSS emergency, the AIS cannot get a vessel position and cannot keep time synchronization for SOTDMA if it does not have any other independent navigation system.
This paper proposes a new scheme for a TOA-based relative navigation system where the TOA is obtained using the AIS datalink if GNSS is not available. The proposed scheme estimates a relative position of a vessel by using other vessel positions including AIS messages and TOA measurements which is obtained by measuring the difference of transmission and reception time of AIS messages. When a vessel broadcasts AIS message including the position via an assigned timeslot of SOTDMA, the other vessels get the positions and TOA measurement to update its relative position. The proposed method will keep the AIS system working even if GNSS is not available. The proposed scheme will be verified and validated using a software-base simulator. KEYWORDS: AIS, Relative navigation, GNSS, Maritime communication
Locata: Implications of a New High Accuracy Positioning System Chris Rizos University of New South Wales/Australia Tel: 61-2-9385-4173, Fax: 61-2-9313-7493 email: email@example.com GPS is a reliable, versatile, generally available and comparatively accurate positioning technology, able to operate anywhere across the globe. GPS is, in fact, the most effective general-purpose navigation tool ever developed because of its ability to address a wide variety of applications: air, sea, land, and space navigation; precise timing; geodesy; surveying and mapping; machine guidance/control; military and emergency services operations; hiking and other leisure activities; personal location; and location-based services. These varied applications use different and appropriate receiver instrumentation, operational procedures, and data processing techniques. But all require signal availability from a minimum of four GPS satellites for three-dimensional fixes. In the coming decade a number of other Global Navigation Satellite Systems (GNSS) and regional systems will be launched. Nevertheless, the most severe limitation of GPS performance will still remain - the accuracy of positioning deteriorates very rapidly when the user receiver loses direct view of the satellites, which typically occurs indoors, in open-cut mines or in severely obstructed urban environments. Furthermore, GPS/GNSS has shown that it is very vulnerable to intentional or nonintentional interference. A new terrestrial RF-based distance measurement technology, trademarked “Locata”, has now overcome the technical challenges required to create “a localised autonomous terrestrial replica of GPS”. UNSW researchers have been investigating Locata technology for over 5 years, in a variety of modes and operational scenarios. Locata is no longer a commercial curiosity. At the Portland 2011 ION Conference Locata demonstrated indoor positioning, it released its ICD, and announced several critical first customers, including Leica Geosystems and the USAF. This paper provides an update on Locata developments, on tests conducted by UNSW, and speculates on the implications for the PNT community of this new positioning technology. KEYWORDS:Locata
GNSS Signal Simulation
1525 - 1705
A Flexible GNSS Signal Generation and Receiver Characterization Platform K J Parkinson (1) N C Shivaramaiah (2) A G Dempster (3) C Rizos (4) School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, 2052, Australia Email for corresponding author: firstname.lastname@example.org A low cost, flexible FPGA-based GNSS signal generator is presented. The aim is to provide a signal prototyping framework to support the research and development of receiver and signal design. Configurable logic devices such as FPGAs (Field Programmable Gate Arrays) together with a software structure provide the required flexibility for efficient multi GNNS signal generation. This framework is a base for both developing new GNSS signals and emulating legacy signals. This allows researchers to explore the tradeoffs between different signal structures in real time including and beyond what is achievable through the software simulation of signals. Three major components are explained: a low phase noise RF (Radio
Frequency) signal source to generate the GNSS carrier signal, logic in the FPGA to modulate the carrier and control software to manage frequency selection and set operating parameters. KEYWORDS: GNSS Signals, simulator, FPGA
Decision of a Time-efficient Software-based GPS Signal Simulator Soon Lim Space Science Division /Korea Astronomy Space Science Institute / Republic of Korea 0428652081, 0428615610, email@example.com Deok Won Lim Satellite Navigation Department / Korea Aerospace Research Institute / Republic of Korea 0428602114, 0428602004, firstname.lastname@example.org Sang Jeong Lee Dept. Of Electronics Engineering / Chungnam National University / Republic of Korea 0428253991, 042, email@example.com Man Soo Choi Space Science Division / Korea Astronomy Space Science Institute / Republic of Korea 0428653244, 0428615610, firstname.lastname@example.org Byung Gyu Choi Space Science Division / Korea Astronomy Space Science Institute / Republic of Korea 0428653237, 0428615610, email@example.com Recently, GPS (Global Positioning System) is used for not military services but also commercial services like shipment or aviation, and it is being modernized by adding more band signals. And Russian government is planning to enhance the performance and continue GLONASS, Galileo and COMPASS are also being developed for providing GNSS (Global Navigation Satellite System) signals by EU and China. So more enhanced positioning performance is expected when various systems such as GLONASS, Galileo and COMPASS are fully operated with GPS. In this situation, the GNSS signal simulator is required for developing a receiver and validating the performance of the receiver. And a software-based signal simulator data is more efficient than a hardwarebased one. Because more many parameters such as the sampling frequency, intermediate frequency, receiver‟s trajectory and simulation environments can be conveniently configured by a user. In case of using a software-based simulator, unfortunately, the running time will increase as the sampling time increases and multiple bands or GNSS signals are generated. And most of the time may be consumed in calculating the satellite‟s position. In this paper, therefore, the GNSS signal simulator that can control an updating time of the satellite‟s position is proposed. And the updating time is calculated by considering the satellites quality. The GNSS signal simulator has been constructed by using C++ language, and the performance has been validated with the NordNAV software receiver. KEYWORDS: GNSS simulator, software simulator, satellite position, receiver trajectory, signal generation
Design of a GPS L1 C/A Signal Generator using a Multi-core Processor SungLyong Cho (1) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org MiHyun Jin (2) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Juhyun Lee (3) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Chansik Park (4) Department of Electronics Engineering/Chungbuk National University/Korea email@example.com Sang Jeong Lee (5) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org
GNSS signal generator is used to mimic real satellite signals. It can be classified into software-based signal generator and hardware-based signal generator. Generally, a software based GNSS signal generator can generate the desired IF or baseband signals at PC. In the software based GNSS signal generator, huge signal processing power is needed and the processing time is likely to be extremely long with a conventional single-core processor. This paper extends the OS kernel based parallel computing GPS L1 C/A signal generator to a parallel programing based one. GPS L1 C/A signal generator using the parallel programing based parallel computing signal generator will consist of user input, satellite orbit generator, navigation generator, error generator, measurement generator and IF signal generator. The performance of the designed signal generator will be improved by using parallel programing. The off-the-shelf multi-core processor and software will be used to implement the signal generator. All the functions in the software generator will be implemented using parallel programing for all satellites. The output of the designed signal generator will be validated with a commercial software defined receiver. KEYWORDS: GNSS; GPS L1 C/A; Signal Generator; Multi-Core Processor
Development of MF-TDMA Based Satellite Network System Simulation Model Sung-Hyung Lee Department of Electronics Engineering, Ajou University, Korea +82-31-219-2474, email@example.com Jae-Hyun Kim Department of Electronics Engineering, Ajou University, Korea +82-31-219-2477, firstname.lastname@example.org This paper describes about development of MF-TDMA based satellite network system simulation model. This model consists of earth station nodes accessing and controlling the network by MF-TDMA scheme. This model also includes channel model of GEO-satellite based communication system such as delay, path loss, atmosphere absorption, and ionospheric effect. Moreover, this model includes dynamic rain fading model with four state Markov chains which models the time interval, fading depth, and variation of rain fading. To verify our simulation model, we gather the changes of signal-to-noise ratio of signal receiver and compare it with rain fading dynamic of real satellite network system. We also measure the network delay using ping command, and throughput using file transmission by FTP, which can be possible by system-in-the-loop function of OPNET simulator. KEYWORDS: MF-TDMA, Network Simulation Model, Satellite Network, OPNET
1525 - 1705
Real-time Indoor Positioning with a Single IMES Transmitter and a Rotation-type Doppler Measurement Unit Yoshihiro Sakamoto Dept. of Modern Mechanical Engineering, Waseda University, Japan phone: 03-5286-3264, fax: 03-5272-0948, email: email@example.com Takuji Ebinuma Dept. of Aeronautics and Astronautics, the University of Tokyo, Japan phone: 03-5841-6972, fax: 03-5841-6976, email: firstname.lastname@example.org Kenjirou Fujii Hitachi Industrial Equipment Systems Co., Ltd., Japan phone: 03-4345-6011, fax: 03-4345-6913, email: email@example.com Shigeki Sugano Dept. of Modern Mechanical Engineering, Waseda University, Japan phone: 03-5286-3264, fax: 03-5272-0948, email: firstname.lastname@example.org The positioning accuracy of IMES, which is part of QZSS, is normally limited to 10â€“20 m because it does not use trilateration. The purpose of this work is to achieve centimeter- to decimeter-level positioning accuracy in real-time under the same condition as the normal use of IMES (that is, the number of visible transmitters of IMES is only one, and trilateration is not used). To accomplish this goal, a real-time Doppler positioning method is proposed. This method uses a rotation-type Doppler measurement unit (which produces the
Doppler shift by rotating a receiver antenna), a three-dimensional attitude sensor, and an extended Kalman filter (EKF) combined with an odometer. To evaluate the proposed method, a positioning experiment with a mobile robot was conducted. Since the robot moved on rails so that slippage does not occur, the positioning accuracy was evaluated in an ideal condition. The experimental results show that centimeter- to decimeterlevel positioning accuracy can be achieved if the velocity error is zero (i.e., no slippage). A simulation was also conducted to examine the influence of the velocity error. In this simulation, positioning was conducted under the condition that the velocity error generated computationally was added to the actual velocity of the mobile robot obtained in the experiment. The simulation results show that a proper modeling of the velocity error in designing the EKF keeps positioning accuracy at an adequate level. KEYWORDS: Doppler Positioning, IMES, Indoor Positioning, QZSS
Preliminary Study on Multi-Station GPS RTK Positioning to Support Emergency Service Operations in Indoor Areas Li Binghao School of Surveying and Spatial Information Systems, University of New South Wales, Australia 02-93854189 email@example.com Wang Jian School of Environment and Spatial Informatics, China University of Mining & Technology, China 15050841419,Wjian@cumt.edu.cn Meng Xiangchao School of Environment and Spatial Informatics, China University of Mining & Technology, China 18795426389,firstname.lastname@example.org Chris Rizos School of Surveying and Spatial Information Systems, University of New South Wales, Australia 02-93854205, email@example.com An indoor positioning system for emergency operations such as fire fighting based on radionavigation principles needs the coordinates of portable transmitters to be determined rapidly and with high accuracy. Generally GPS real-time kinematic (RTK) positioning requires tracking of 4 or more satellites with good geometric distribution to provide centimetre-level accuracy. In urban canyons, however, high buildings block signals from satellites with low to medium elevation angles hence significantly decrease the number of visible satellites and degrade the geometric distribution. Utilising â€œcooperative measurementsâ€? may make positioning possible even under such situations. In this preliminary study, one reference receiver and two rover receivers are utilized. The reference receiver which locates at an open sky environment with known coordinates observes a sufficient number of satellites, whereas the rover receivers can only observe three satellites respectively as a result of building blockage. The distance between the rovers is used as constraint (or cooperative measurement) to improve the observing conditions. The static testing results showed that the solution with distance constraints achieves better accuracy since it increase the possibility to resolve the integer ambiguities and enhance the availability of fixed ambiguity solution compared with GPS alone. In a GPS unfriendly environment, at least decimetre accuracy can be maintained. KEYWORDS: GPS; RTK; urban canyon; cooperative positioning; ambiguity resolution
An Enhanced Ranging Scheme Using Adaptive Log Model Based on IEEE 802.11 RSSI Measurements A Sol Kim School of Electronics Engineering Kyungpook National University Daegu, Korea firstname.lastname@example.org Do Woo Park School of Electronics Engineering Kyungpook National University Daegu, Korea email@example.com Joon Goo Park School of Electronics Engineering Kyungpook National University Daegu, Korea firstname.lastname@example.org The LBS (Location Based Service) is becoming important part of IT(Information Technology) business. The localization is a core technology for LBS, because the LBS based on a position of each device or user. In case of outdoor, GPS is used to get a position of moving user as dominant technology. But as for indoor environments, GPS is not available. Therefore, for â€žSeamless LBSâ€&#x;, an enhanced indoor localization scheme which produces a similar position accuracy to that of GPS is needed. In case of a wireless network, such as IEEE 802.11, a method using a received signal strength indicator (RSSI) for each access point is advantageous because it does not require additional infrastructure and it is suitable for the simplification. In this paper, we will propose dual Log Model that has variable parameters based on WLAN RSSI measurements. KEYWORDS: indoor localization, received signal strength indicator, dual log model, variable parameter
Indoor Positioning Based on FM Signals and Wi-Fi Signals Vahideh Moghtadaiee (1) PhD student, School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Phone: +61 2 9385 4185 / Fax: +61 2 9313 7493 / Email: email@example.com Andrew G. Dempster (2) Professor & Director of Research, School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Ph: +61 2 9385 6890 / Fax: +61 2 9313 7493 / Email: firstname.lastname@example.org Samsung Lim (3) Associate Professor, School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Ph: +61 2 9385 4505 / Fax: +61 2 9313 7493 / Email: email@example.com With increasing user demands on Location-based Services (LBS) and Social Networking Services (SNS), indoor positioning has become more crucial. Because of the general failure of GPS indoors, non-GNSS navigation technologies are essential for such areas. Utilizing signals of opportunity is a promising alternative navigation method providing adequate geo-location. Wireless Local Area Networks (WLAN) have been used for localisation indoors. In this study, however, a new positioning system is proposed based on another signal of opportunity: broadcast FM. This analogue audio signal has some advantages for indoor positioning purposes over Wi-Fi signals, such as the ability to be received both indoors and outdoors, dense coverage, availability, low-cost and low-power hardware, and high received signal power. In this paper, along with comparing FM and Wi-Fi positioning systems, we increase position accuracy by fusing both methods. The indoor localisation system suggested here utilises the fingerprinting technique based on FM received signal strength. The fingerprinting implementation involves two stages, the training stage and the positioning stage. The matching algorithms used in the fingerprinting method in this work are Nearest Neighbour (NN), KNearest Neighbours (KWNN), and the K-Weighted Nearest Neighbours (KWNN). The proposed localisation was tested experimentally. The mean distance error (MDE) is about 3m when the KWNN algorithm utilised. The results indicate that FM error was higher than for Wi-Fi; however, FM costs much less due to availability, degree of coverage, and simplicity of the receivers. An improvement of 11% is achieved in positioning error when FM and Wi-Fi measurements are combined.
KEYWORDS: Fingerprinting technique, broadcast FM signal, indoor location, received signal strength.
Feasibility Study of Seamless Positioning System Using QZSS IMES Yutaka Yamada Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Japan +81-3-5245-7365 firstname.lastname@example.org Akio Yasuda Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Japan +81-3-5245-7365 email@example.com
IMES (Indoor Messaging System) is a positioning technology for indoor positioning system. IMES signal specification is similar structure as of QZSS (Quasi-Zenith Satellite System) and GPS, called “IMES L1 C/A” and defined in IS-QZSS. IMES‟s concept is compatible and interoperable with QZSS and GPS for seamless positioning. The US Government has allocated PRN Codes (173 to 182) for the ground use of L1 C/A code in Japan. However, IMES signal transmitter is “Low Power Radio Station” prescribed “Radio Act”. For example, the level of the strength of the radio wave is limited. This paper presents result of demonstration experiment based on above concept. The story is to define available distance at the combination of power level of IMES signal transmitter and receiver sensitivity, to fix the position by ranging based on IMES and to develop seamless indoor/outdoor positioning system utilizing multi-GNSS receiver of GPS, QZSS and IMES. This paper also presents feasibility study of seamless positioning system, which can be realized by the satellite signals outdoor and IMES signals indoor. We will ensure interoperability of Japan's original positioning technology IMES included in the satellite system QZSS with GPS. KEYWORDS: seamless positioning, IMES, QZSS, indoor, outdoor
Abstracts – Wednesday 16 November, 2011 Session 5:
0845 – 1045
U.S. Space-Based Positioning, Navigation and Timing: A Policy and System Update Maureen Walker U.S. Department of State Representative to the National Space Based Positioning, Navigation and Timing Coordination Office Washington, D.C. 20230 Scope: This presentation will focus on the development of the U.S. space-based positioning, navigation and timing policy. It will review the background of that policy and will look at measures that have been taken to implement the policy. The talk will address the establishment of the National Space-based PNT Executive Committee and provide some insight into the issues that are currently under consideration. U.S. Approach: Questions concerning the U.S. modernization schedule will be addressed in the U.S. presentation. GPS modernization and the associated implementation of the two new Global Positioning System (GPS) civil signals, completion of ongoing civil augmentation systems, and finally, the compatibility and interoperability with other providers and potential providers will be discussed. These new signals, L2C and L5, coupled with the L1 band, are improving the positioning, navigation, and timing capabilities that GPS provides to the vast array of civil and commercial applications. New international structures are taking into account the increasing global nature and use of GPS as well as other GNSS systems. The presentation will include a brief summary of U.S. collaboration with other GNSS providers. st
Conclusion: Satellite navigation will be one of the key enabling technologies of our future 21 century transportation and airspace management system. GPS has provided worldwide users with navigation, positioning, and timing services since becoming operational in late 1993. The United States hopes to improve those services through modernization, augmentations, and working closely with other GNSS providerse.
GLONASS Evolution Alexander BOCHKAREV Deputy head of International Cooperation Directorate/Roscosmos/Russia Phone +7 495 631 85 21 Fax: +7 495 631 90 24 email firstname.lastname@example.org Alexey LUSHIN Head of department of International Cooperation Directorate/Roscosmos/Russia Phone +7 495 631 85 21 Fax: +7 495 631 90 24 email email@example.com Vladimir FILATOV Expert of International Cooperation Directorate /Roscosmos/Russia Phone +7 495 631 85 21 Fax: +7 495 631 90 24 email firstname.lastname@example.org Svyatoslav ANDRIANOV Consultant of GLONASS Directorate/Roscosmos/Russia Phone +7 495 631 85 21 Fax: +7 495 631 90 24 email email@example.com Yuri URLICHICH General director – general designer, GLONASS general designer/Russian Space Systems/Russia Phone +7 495 509 12 01/Fax +7 495 509 12 00 email firstname.lastname@example.org Grigory STUPAK Deputy general director – general designer, deputy GLONASS general designer/Russian Space Systems/Russia Phone/Fax +7 495 673 93 99 email email@example.com Vyacheslav DVORKIN PNT systems general designer/Russian Space Systems/Russia Phone/Fax +7 495 673 28 15 email firstname.lastname@example.org Sergey KARUTIN Deputy head of division/Russian Space Systems/Russia Phone +7 495 673 97 29 Fax +7 495 673 28 15 email email@example.com The main phase of GLONASS system developmenthas been coming to the end in 2011. At the moment
there are twenty eight navigation satellites, including twenty four regular, three reserve "Glonass-M" satellites and one "Glonass-K". Launches of four “Glonass-M” and one “Glonass-K” are planned to carry out by the end of this year. It will allow to create the conditions for continuous global navigation service to GLONASS users. Development of GLONASS space complex will be continued by creation of the following generation satellite "Glonass–K2" which will transmit additional CDMA navigation signals in L1 and L2, L3 bands. In the second half of 2011 year the launch of GEO satellite "Luch–5A" is planned with the system of differential correction and monitoring (SDCM) transponder on-board. SDCM is the first SBAS system which transmits the corrections to ephemeris and clocks for GLONASS and GPS satellites. These facts create a strong basis for the further GLONASS development. Main directions of this development are the implementation of new CDMA navigation signals and improving precise positioning technology on GLONASS and SDCM basis. KEYWORDS: GLONASS, CDMA signals, GNSS augmentations.
The Demonstration Result for the First Satellite of the Quasi Zenith Satellite System, Michibiki Mr Satoshi Kogure, Japan Aerospace Exploration Agency. Ibaraki, JAPAN Abstract not provided
Update on China's Beidou System Mr Matt Higgins President, IGNSS Society Abstract not provided
Update on Light Squared Interference to GPS in the US Prof Andrew Dempster The University of New South Wales, AUSTRALIA Abstract not provided
NavRange Venkatraman Ramkumar ESNC 2011 Winner â€“ Australia +61422877072 firstname.lastname@example.org NavRange is a GNSS-based golfing system which tracks & plots the speed, position, spin, bounce and flight of a ball in play. It then downloads all this information via NavRange software, using visual animations of the golf course and ball trajectory to allow the user to see in near real time how the ball was hit. Scoring is also done automatically; with the possibility of uploading the results to the internet. This idea has won the European Satellite Navigation Competition (ESNC) 2011 for Australia. KEYWORDS: ESNC, GNSS, Golf, Sport
CORS - Heights
1120 - 1240
Evaluation of NRTK Heighting in Victoria: Impact of a Temporary Reference Station Eldar Rubinov, Grant Hausler, Phil Collier Cooperative Research Centre for Spatial Information, Australia email@example.com, firstname.lastname@example.org, email@example.com Jarryd Poyner The University of Melbourne, Australia Gavin Docherty Position Partners, Australia James Millner Department of Sustainability and Environment, Victoria, Australia Desmond Elliott GLOBAL CORS, Australia Network Real-Time Kinematic (NRTK) positioning is a mature technology that has been proven superior to conventional single-base RTK. NRTK typically delivers improved accuracy, better service reliability and coverage, and a more consistent datum realisation compared to a single-base solution. In the horizontal plane, NRTK consistently meets manufacturersâ€&#x; specifications, however practical experience reveals that NRTK-derived heights are less reliable and often fall short of requirements. Height discrepancies in the order of 5-10cm have been observed under various operating conditions, reducing the benefit of this technology for some users. This paper aims to evaluate the quality of heighting that can be achieved in Victoria using three different 3 NRTK solutions (VRS Net, TopNET, and Checkpoint) compared with a single-base RTK solution. A Temporary Reference Station (TRS) is also introduced to densify an existing CORS network to evaluate whether its inclusion offers any significant benefits to the quality of heighting results. It was found that the three NRTK solutions provided similar levels of performance, and that the inclusion of the TRS reduced the average height error from 25mm to 20mm. KEYWORDS: NRTK, CORS, TRS, heighting, quality assessment
Maximum CORS Baseline Lengths for Accurate GNSS Heighting in Australia Gavin Docherty UNSW/Position Partners/Australia Ph: 61-400 354 873 email: firstname.lastname@example.org Craig Roberts School of Surveying and Spatial Information Systems University of New South Wales / Australia Ph: 61-2-9385 4464 email: email@example.com This paper investigates CORS inter-reference station distance constraints for the GNSS networks providing network RTK at times of high ionospheric disturbance. The scientific and commercial communities generally recommend between 70 and 80km as the maximum distance between CORS. The average distance between all reference stations within the Victorian state wide GNSS CORS network (the most established and dense network in Australia) is about 78km. This study will focus on the adequacy of this density to
provide end users with consistent, accurate heights in an acceptable time to first fix and at times of high ionospheric activity. This paper will also explore some of the possible remedial strategies in areas that are deemed to require a higher density of reference stations for high accuracy height requirements such as Temporary CORS Stations (TCS). This study will not provide a definitive value for this inter-reference station distance limit, but will determine if the current service levels are acceptable for a height sensitive user and if the heighting performance is improved by including a TCS in the proximity of the “project site”. These questions are increasingly significant to Australia‟s spatial community as all GNSS real time positioning service providers, both Government and commercial, begin to collaborate to create not only a geodetic reference framework for Australia but a ubiquitous national CORS network. Finally, this paper will examine some of the ionospheric disturbances that have affected network RTK solutions in the mid latitudes of Europe and attempt to predict similar effects in Australia in the upcoming solar peak period (Solar Cycle 24). KEYWORDS: CORS, MSTID, Solar Cycle, Network RTK, Baseline
AHD Coordination of CORS Sites Using GNSS Simon Fuller ThinkSpatial firstname.lastname@example.org Dr Roger Fraser Department of Sustainability and Environment, Victoria email@example.com Jacqueline LeLievre Department of Sustainability and Environment, Victoria firstname.lastname@example.org Steven Ferraro Department of Sustainability and Environment, Victoria In recent years there has been a significant expansion in the number of Continually Operating Reference Station (CORS) sites and networks throughout Australia. In Victoria alone, the number of CORS in the Department of Sustainability and Environment managed Vicmap Position - GPSnetTM (GPSnet) network has increased threefold since 2008. One of the practical challenges faced as a result of this expansion is the rigorous, efficient, and safe connection of newly constructed sites to the Australian Height Datum (AHD). Traditionally such a task would be undertaken using terrestrial techniques, however the large number of sites to be coordinated, budget pressures, logistical issues, and occupational health and safety constraints dictate that an alternative approach be employed. Further complicating the problem is a desire to incorporate the CORS sites into current (and future) regional geoid models, such as AusGeoid09. Thus, the use of such models in determining the AHD Reduced Level of the CORS (in a classic GNSS heighting scenario) would be inappropriate. This paper addresses these challenges by detailing a rigorous, efficient, and practical method for the connection of CORS sites to the AHD using GNSS in the absence of a regional geoid model. The background and drivers for the development of the method are discussed (in the context of GPSnet) prior to providing a detailed description of the method and the conditions for its use. Following this, the results and an analysis of a comparison between traditional techniques and the method described in the paper are presented. The comparison demonstrates the suitability of the method for providing AHD connections using GNSS in the absence of a regional geoid model. The paper concludes with a brief discussion on the significance of the comparison and the applicability of the method, suggestions for further testing, and potential improvements to the method outlined in the paper. KEYWORDS: AHD, GNSS, CORS, Heighting.
GPS/Other Sensor Integration (1)
1120 - 1240
Design and Implement of a MEMS-based Attitude Reference System and its Integration with GPS LI Rongbing Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-809 & + 86 25 84892304-819, email@example.com LIU Jianye Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-801 & + 86 25 84892304-819, firstname.lastname@example.org SUN Yongrong Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84896155 & +86 25 84892304-819, email@example.com HANG Yijun Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-825 & +86 25 84892304-819, firstname.lastname@example.org With the rapid development of MEMS inertial sensors, the accuracy and integration level are increased sustaining and the MEMS-based micro inertial system has become very necessary in aero vehicles and guided munitions. This paper investigated a micro inertial attitude system and its integration system with GPS. In the design of the MEMS-IMU, timer-interrupt and SPI FIFO interrupt based multichannel high speed data sampling method for MEMS gyros and the 24bit ADC electric circuits are used. Process integration of the micro system is optimized. The micro inertial integration system can work in two modes of inertial attitude and GPS/IMU integration. Kalman filters were used in both of modes. The micro attitude system took the accelerometers in the MEMS-IMU as tilt sensor to form the attitude observation vector and the noise variance was tuned adaptively according to the dynamic process. Based on the integration of the MEMSIMU, GPS/MEMS-INS integrated navigation system was researched further. Some experiments and tests were carried on to validate the design of MEMS-IMU. The bias drift with temperature and the non-orthogonal alignment of MEMS inertial sensor modules were modelled and the performance tests of the micro inertial system were done and the result shows the static accuracy of 0.7 deg and dynamic accuracy of 1.5 deg in the environment from -45â„ƒ to 70â„ƒ.The micro inertial integrated system can be used to the determination of small UAV and attitude backup for aircraft and shows its wide application aspects. KEYWORDS: MEMS-IMU, attitude reference system, GPS/MEMS-INS.
Test Results of a Wireless Sensor Networks Assisted Global Navigation Satellite System (WSN-AGNSS) Ali Sarwar School of Surveying and Spatial information Systems, UNSW, Australia Phone : +61 2 9385 4185, Fax : +61 2 9313 7493 Email: email@example.com Eamonn Glennon School of Surveying and Spatial information Systems, UNSW, Australia Phone : +61 2 2 93137493, Fax : +61 2 9313 7493 Email firstname.lastname@example.org Chris Rizos School of Surveying and Spatial information Systems, UNSW, Australia Phone: +61 2 9385 4205, Fax: +61 2 9313 7493, Email: email@example.com The performance and availability of Stand-Alone Global Positioning or Navigation Satellite Systems (GPS) or (GNSS) have been questionable indoors pertinent to poor sky visibility and multipath. Location Based Emergency Systems are time and availability critical applications requiring much resilient positioning which can guarantee availability in reasonable time frame. GPS, GNSS or Assisted GNSS would normally require basic electrical and networking indoor infrastructure to respond and not always suitable for emergency relief provisioning applications. The application of interest is indoor fire fighting in destroyed infrastructure where In-building Coverage (IBC) repeaters are damaged and mobile phones services are hampered. This paper presents an alternative strategy to augment GPS with Wireless Sensor Nodes (WSN). Fixed sensor nodes are deployed in the test area and rover sensor node is connected with laptop and GPS. Based on received signal strength (RSS) algorithm, signature indexes are generated and proximity calculations are made by fixed nodes to locate the rover. The location information is transferred to the GPS or GNSS device for assistance. Experimentation was conducted in School of Spatial Information Systems (SSIS), University of New South Wales (UNSW) to simulate a potential reduction in the GPS navigation search space. This improves Time to Fix First (TTFF), availability and accuracy. This system based on 10 fixed nodes providing
assistance to the rover node augmented GPS posed a better tendency to offer redundancy in partial system or node failure. Test results prove a better relative performance than competing technologies e.g. StandAlone GPS, Assisted GPS and SPOT Satellite Messenger in indoor environments. More general applications may include assistance in natural disasters on larger scales due to ease of rapid deployment possibilities of the system. KEYWORDS: WSN, Assisted GNSS, Indoor Positioning, Accuracy, TTFF
Design of an Integrated Navigation Algorithm for eLoran/GNSS Receiver Se Phil Song (1) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Heon Ho Choi (2) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Chansik Park (3) Department of Electronics Engineering/Chungbuk National University/Korea firstname.lastname@example.org Sang Jeong Lee (4) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Loran-C is a ground based navigation system which uses TDOA(Time Difference of Arrival) measurements of strong signal power. But Loran-C had been steeply declined and replaced by GPS because of its low accuracy. And GNSS satellite navigation system such as GPS or GLONASS becomes more important infrastructure for PNT(positioning, navigation and timing). Because satellite navigation system is vulnerable to interferences due to the low received signal power, the requirement of the complementary navigation system is increasing. Therefore, many countries are attempting and deliberating to enhance current Loran-C system as a complementary and supplementary navigation system. eLoran is an improved Loran-C system which uses TOA(Time of Arrival) measurements instead of TDOA measurements and dLoran(differential Loran) technology to remove ASF(Additional Secondary Factor). Using the integrated eLoran and GNSS navigation algorithm, the ASF can be easily compensated and a precise eLoran positioning is possible when GNSS is not available. Two integration algorithms are widely adopted: position domain and pseudo-range domain. Position domain integration is easy to implement, but it cannot find position when the number of GNSS or eLoran signals are less than 4. Pseudo-range domain integration uses both GNSS and eLoran pseudo-range measurement at a navigation filter to find the position; therefore, the availability is increased. This paper proposes an integrated eLoran/GNSS navigation algorithm which efficiently combines position domain and pseudo-range domain integration method. The proposed algorithm will combine position domain solution if they are available. If not, it uses the pseudo-range domain integration method. An optimal weighting for position domain integration is derived and applied to give the equivalent results of pseudo-range domain integration with much less computations. Proposed methods will include several integration modes such as GPS L1/L2, GPS/GLONASS, eLoran/GPS and eLoran/GPS/GLONASS. The proposed eLoran/GNSS navigation algorithms will be evaluated and compared with the standalone navigation method by using the test platform. KEYWORDS: eLoran, GPS, GLONASS, GNSS, Navigation method
Image-Based Positioning with the Use of Geo-referenced SIFT Features Xun Li School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Phone: +61 2 9385 4185 Fax: +61 2 93137493 email: firstname.lastname@example.org Jinling Wang School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Phone: +61 2 9385 4203 Fax: +61 2 93137493 email: email@example.com Ruiyuan Li School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Phone: +61 2 9385 4203 Fax: +61 2 93137493 email: firstname.lastname@example.org Weidong Ding School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia
Phone: +61 2 9385 4203 Fax: +61 2 93137493 email: email@example.com In this paper, our early proposed image-based positioning method is implemented via the geo-referencing of SIFT feature points as natural landmarks for positioning. The main contribution is the adoption of georeferenced SIFT feature points as control points for positioning, which avoids the common drifting errors in available image-based navigation systems. Experiments prove the possibility of such method to be used as an absolute positioning tool in GPS-denied environment, and also reveal the limitation and potential improvement. KEYWORDS: Image-based navigation, SIFT, geo-referencing
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An Efficient Signal Quality Test of RTK-GNSS Based on Carrier to Noise Ratio Nobuaki Kubo (1) Tokyo University of Marine Science and Technology 03-5245-7376 firstname.lastname@example.org Tomoko Shirai (2) Tokyo University of Marine Science and Technology Quasi-Zenith Satellite (QZS) â€œMichibikiâ€? was launched successfully by the H2A Launch Vehicle on September 11, 2010. The performance evaluation using GPS+QZS has been simulated for several years. In this paper, the overall real performance evaluation was conducted from stand-alone positioning to RTK positioning under several environments. As we expected, the effect of QZS on performance improvement was clearly notable especially in the urban areas. For example, the fixing rate of ambiguity resolution in a single epoch was improved from 46 % using only GPS observation data to 69 % using GPS+QZS observation data obtained by the car in Tokyo. Also the new signal quality test algorithm was proposed in this paper. Based on the number of our experimental results, it was revealed that the diffraction frequently induced the wrong fixes in RTK. To cope with this problem, we found that it is effective to use carrier-tonoise ratio in both L1-C/A and L2P(Y) signal for the signal quality test. From our experimental results, the proposed technique was effective not only reducing positioning errors but also increasing availability. KEYWORDS: RTK, QZS, Multipath, Signal quality test.
Effect of L1-SAIF Augmentation in GPS Positioning Xing BO Tokyo University of Marine Science and Technology /Japan +813-5245-7365, email@example.com Tomoji TAKASU Tokyo University of Marine Science and Technology / Japan +813-5245-7365, firstname.lastname@example.org Akio YASUDA Tokyo University of Marine Science and Technology/Japan +813-5245-7365, email@example.com L1-SAIF (L1 Submeter-class Augmentation with Integrity Function) signal is one of the navigation signals of QZSS (Quasi-Zenith Satellite System), which provides augmentation function for mobile users of GPS in Japan. This paper investigates the effect of the L1-SAIF augmentation in GPS positioning. The QZSS satellites broadcast GPS-compatible ranging signals including the wide-area augmentation channel (L1-SAIF signal). L1-SAIF has been developed based on SBAS standard because both of them will offer similar function to the almost same service area. Raw data have been collected by the JAVAD receiver from January 18, 2011 to May 19, 2011 at a rate of once per 10 seconds. The raw data have been processed in a number of modes; (1) Stand-alone position calculation based on pseudo ranges of GPS only, (2) DGPS calculation by MSAS correction data, and (3) DGPS calculation by L1-SAIF correction data. Positioning results show that, for the augmented positioning, 2drms of DGPS calculation by L1-SAIF and MSAS messages are about 1.5 m and very close to each other. This is mainly because the L1-SAIF only includes the SBAS (MSAS) compatible messages at the moment. The service area of L1-SAIF is smaller than MSAS because the content of L1-SAIF is different from MSAS, although their formats are the same. The L1-SAIF extension messages including QZSS correction are expected to be transmitted in the future. KEYWORDS: QZSS, L1-SAIF, MSAS, DGPS, augmentation message
Evaluation of Positioning Accuracy of GNSS with QZSS Augmentation Yong Li University of New South Wales/Australia Tel: 61-2-9385-4173, Fax: 61-2-9313-7493 email: firstname.lastname@example.org Chris Rizos University of New South Wales/Australia Tel: 61-2-9385-4205, Fax: 61-2-9313-7493 email: email@example.com The Japanese Quasi-Zenith Satellite System (QZSS) is primarily designed to augment the GNSS visibility in urban environments where there is high density of tall buildings and/or narrow streets. The first QZSS satellite (â€œMichibikiâ€?) was launched in September 2010. It began broadcasting navigation signals in October 2010. The signals were evaluated by some investigators in December 2010. The Javad company has developed firmware which enables the tracking of all QZSS signals except for the LEX. A receiver with the special Javad firmware has been installed in the School of Surveying and Spatial Information Systems at the University of New South Wales (UNSW), together with three other stations in the QZSS service area, which are components of the global CONGO network established by the German Aerospace Centre (DLR). The tracked GNSS signals include those of GPS, GLONASS, Galileo, and QZSS. The data are being analysed and being used for the computation of the orbit and clock errors of Michibiki. This paper describes the strategy of data analysis and presents preliminary results. Combining the GPS, GLONASS and the QZSS satellite (with high elevation angle in its service area), the GNSS availability in an urban environment is improved. The navigation software to process the GNSS data is under development at UNSW. Cooperating with the DLR, the orbit and clock solutions of Michibiki are computed, which are then applied in the data processing to improve the accuracy of the navigation solution, as well as to evaluate the accuracy of the carrier phase measurements of the QZSS. The benefits of using QZSS for precise point positioning (PPP) will be discussed. KEYWORDS:GNSS, QZSS, navigation algorithm, PPP.
1120 - 1240
An Ionospheric Delay Model for Pedestrian Navigation in East Asia Pacific Islands An-Lin Tao Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: firstname.lastname@example.org Shau-Shiun Jan Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: email@example.com Ming Yang Department of Geomatics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2757575 ext. 63820 / email address: firstname.lastname@example.org The ionosphere is a main source of GPS error. In the areas where the magnetic latitude is low, for example the East Asia Pacific Islands, the ionosphere effects are even more severe. The goal of this paper is to develop an ionospheric delay model to correct this error for pedestrian navigation system in the East Asia Pacific Islands region. The ionospheric delay model is similar to the thin shell planar fit model used in the satellite based augmentation system (SBAS). However, the five-degree ionospheric grids for the SBAS do not provide sufficient resolution in the East Asia Pacific Islands regions. Most of the lands in the area lay entirely in one five-degree ionospheric grid, and the grid model used in the SBAS gives a flat value to the ionospheric delay estimate for the whole island. As a result, this paper develops a more dynamic planar fit model with four dual-frequency GPS reference stations distributed geometrically in Taiwan, and this dynamic planar fit model uses the vertical ionospheric delays of all the ionospheric pierce points observed by the four reference stations as the scattered sample points to provide ionosphere corrections to the pedestrian navigation systems through some communication networks. The developed dynamic ionosphere model is detailed in this paper, and the results of the performance comparison study between this developed model and the conventional five-degree planar fit model are shown as well. KEYWORDS: Ionospheric delay model; GPS; Pedestrian navigation.
High Performance GNSS Augmented Pedestrian Navigation in Signal Degraded Environments Jared B. Bancroft University of Calgary, AB, Canada 0011 1 403 210 9802, email@example.com M. Haris Afzal University of Calgary, AB, Canada 0011 1 403 210 9797, firstname.lastname@example.org Gérard Lachapelle University of Calgary, AB, Canada 0011 1 403 220 7104, email@example.com Pedestrian navigation is commonly performed with GNSS. GNSS signals are nearly always degraded due to antenna location on users and signal blocking by buildings, trees and indoor. Additional sensors are therefore used to overcome the above effects and enhance availability, accuracy and reliability. These sensors do not rely on external RF signals, thereby providing complementarity where RF signals are likely to fail and can be divided into two groups. The first group consists of accelerometer and rate gyro triads that rely on the earth‟s gravity, which is stable and time invariant for the purpose and stable for earth users. The second group consists of barometers and magnetometer triads, which are affected by ambient atmospheric pressure in the first case and the Earth‟s magnetic field and its natural and man-made anomalies in the second case. Magnetometers, although naturally complementary with rate gyros, are particularly prone to rapid fluctuations in the indoors, thereby being of limited value so far. In this paper, the authors present and investigate an enhanced method to combine the above sensors with GNSS for applications in severe urban canyon and indoor environments. A novel approach is use to combine magnetometer and rate gyro measurements in the above environments to maintain effective orientation. Test results in actual degraded environments demonstrate the effectiveness of this approach by comparing the outputs of different solutions, e.g. GNSS versus GNSS + inertial sensors versus GNSS + inertial sensors + magnetometers + barometers. The differences in availability and accuracy between the solutions serve to illustrate the performance advantages of the method proposed. KEYWORDS: Pedestrian Navigation, Integration, Fusion, Inertial Navigation, Multi-sensors
Implementation of GPS RTK/MEMS IMU Integrated System using Embedded Platform for Vehicle Navigation Jong-Hwa Song (1) Department of Electronics Engineering/Konkuk University/South Korea firstname.lastname@example.org Gyu-In Jee (2) Department of Electronics Engineering/Konkuk University/South Korea email@example.com In urban area, the GPS RTK (real-time kinematic) can't provide a continuous and an accurate solution as open sky condition. Because the lower and frequent change of satellite number, multipath, cycle slip, loss of carrier lock and discontinuous of data link deteriorate the integer ambiguity resolution when GPS receiver operates between high buildings, respectably. The GPS RTK/IMU integration system can be used as one of method to overcome this problem. The IMU provides the navigation solution when GPS tracked satellite is less than four and help the cycle slip detection. In addition, measurements aiding reduce the integer fixing time and improve the solution accuracy. In this paper, we represent the implementation of the real-time low-cost GPS RTK/MEMS IMU integrated System for vehicle navigation. We deal with implementation issues such as time synchronization and MEMS IMU mechanization. The implemented GPS RTK/IMU system consists of high sensitivity GPS L1 receiver and low-cost MEMS IMU. We use the U-Blox‟s LEA-6T module for GPS carrier phase measurement reception. The used MEMS IMU is Analog device‟s ADIS16405 which is automotive grade IMU. The MEMS IMU includes a tri-axis gyroscope, accelerometer and magnetometer to improve the heading data accuracy. For real-time communication with reference station, we use the HSDPA modem and serial to PPP (point to point protocol) network converter. The car experiment is performed to demonstrate the performance of proposed system.
KEYWORDS: GPS RTK, MEMS IMU, Embedded System
A Low-cost Pedestrian Navigation System in a Signal Degraded Environment Younsil Kim Mechanical and Aerospace Engineering/Seoul National University/South Korea +82-2-880-8918(phone), +82-2-876-6649(fax), firstname.lastname@example.org Am Cho Korea Aerospace Research Institute email@example.com Changdon Kee Mechanical and Aerospace Engineering/Seoul National University/South Korea +82-2-880-1912(phone), +82-2-888-2069(fax), firstname.lastname@example.org This paper presents GPS/PDR algorithm for pedestrian navigation system using low-cost GPS receiver and MEMS IMU in a signal degraded environments. Kalman filter is used as an estimating technique for integrating GPS position and step length. The goal of this research is improve the position estimation accuracy in a signal degraded environments through GPS position measurement noise variance amplitude modelling. The heading is calculated by using GPS heading and gyro output. And the position is estimated by using GPS position and step length. In experimental results, the proposed algorithm has better position estimation performance than conventional method, constant measurement noise variance modelling. The performance of the proposed algorithm is verified through the actual walking test. KEYWORDS: Pedestrian Navigation, Pedestrian Dead Reckoning, GPS/PDR Integration
CORS - Deployment & Use Proudly sponsored by Position Partners
1340 - 1500
CORSnet-NSW: Deploying a CORS Network in a Corporate IT Environment Thomas S. Yan Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services 1 Prince Albert Road, Sydney NSW 2000, Australia Phone: +61 2 6332 8389 Fax: +61 2 9233 4133 Email: Thomas.Yan@lpma.nsw.gov.au
Charles K. Jap Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services 1 Prince Albert Road, Sydney NSW 2000, Australia Phone: +61 2 8257 2971 Fax: +61 2 9233 4133 Email: Charles.Jap@lpma.nsw.gov.au CORSnet-NSW is an expanding network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) being deployed in New South Wales, Australia by Land and Property Information (LPI), the State‟s lead agency for spatial data infrastructure. It currently consists of more than 60 CORS across NSW with two redundant Network Control Centres (NCC) in two geographically separate data centres. Within LPI, all IT resources are centrally managed by a team of specialists in the Information & Communications Technology (ICT) section. The NCCs for CORSnet-NSW have been jointly designed and implemented by the Survey Infrastructure & Geodesy and ICT sections of LPI. This paper examines the approach taken in designing and implementing a NCC for a CORS network on top of a corporate IT infrastructure. New technologies such as Virtual Private Network (VPN) and server virtualisation – commonly used in the corporate IT environment today – are employed and their specific implementation in CORSnetNSW will be discussed. The advantages and disadvantages of using such an approach at LPI will also be examined. KEYWORDS: CORS, IT, CORSnet-NSW, virtual server, VPN
On CORS Site Stability Monitoring Guorong Hu Geospatial and Earth Monitoring Division, Geoscience Australia Tel: 02-6249 9884; Fax: 02-6249 9969; Email: Guorong.Hu@ga.gov.au John Dawson Geospatial and Earth Monitoring Division, Geoscience Australia Tel: 02-6249 9028; Fax: 02-6249 9969; Email: John.Dawson@ga.gov.au The number and distribution of GNSS CORS networks has steadily increased over the past two decades. Monument types vary from concrete pillars to fence posts which reflect the varying requirements of the broad CORS user community. Site stability monitoring is an important part of maintaining a robust CORS network. With a growing dependency on GNSS data and legal traceability of GNSS data back to the datum, it has never been more important to monitor the stability of a CORS site. Site stability surveys provide assurance that the CORS data reflects geophysical change in the area, not instability of the monument. By monitoring and characterising CORS station behaviour, users can be assured of high quality data. Monument instability results in higher noise levels and makes it difficult to discern the long-term velocity of the site. This is particularly challenging for tectonic analysis using GNSS. This paper discusses strategies for monitoring site stability at the observation and site position level. Case studies are presented with emphasis on the accuracy and precision of CORS site positions through both epoch by epoch solutions and daily station coordinate solutions. Initial results show: 1) in terms of standard deviations of position offsets, a significant reduction in noise can be seen when comparing deep drilled braced monuments to rooftop monuments, the biggest reductions are 4.4 mm, 4.3 mm and 3.3 mm in the east, north and vertical components, respectively; and 2) stations with small position residuals were well designed and followed the IGS site guidelines.
KEYWORDS: CORS, Monumentation, Stability
Network-based RTK Positioning Using Integrated GPS and GLONASS Observations Shaocheng Zhang SPACE Research Centre, RMIT University, Australia Phone: (+61) 3 99253709 Shaocheng.Zhang@rmit.edu.au Kefei Zhang SPACE Research Centre, RMIT University, Australia Phone: (+61) 3 99253272 Kefei.Zhang@rmit.edu.au Suqin Wu SPACE Research Centre, RMIT University, Australia Phone: (+61) 3 99252114 Suqin.Wu@rmit.edu.au Binghao Li School of Surveying and Spatial Information Systems, UNSW, Australia Phone (+61) 2 93854189 Binghao.Li@unsw.edu.au With the recent rapid revival of the GLONASS constellation, it is possible for the GLONASS system to provide Full Operational Capability (FOC) service before the end of 2011. Also CDMA signals had already modulated on the first GLONASS-K satellite which was launched on February 26, 2011. It is envisaged that GNSS users will be benefited from more visible satellites, and better precision and higher reliability of positioning. This research focuses on using integrated GPS and GLONASS observations for Network-based RTK positioning. In order to fix double-differenced GLONASS ambiguities, the frequency-based inter-channel biases are calibrated first using a short static baseline; then with the calibrated inter-channel bias, the double-differenced ambiguities for CORS baselines .are fixed and the tropospheric and ionospheric delays are also calculated, and in the final step the values of the tropospheric and ionospheric delays are interpolated for the rover user in the form of VRS observation. At the rover side, the GPS and GLONASS integrated positioning results are obtained using a simulated RTK processing. In this paper, data from the Sydney CORS network was used to test and validate the proposed GPS and GLONASS integrated Network-RTK algorithm. Results showed that after the ambiguities of the CORS baselines are successfully fixed, the tropospheric and ionospheric delays can be interpolated into centimetres level accuracy, and the positioning results of the rover receiver showed 96.1% success rate of single epoch ambiguity resolution with the standard deviations of 0.8, 1.0 and 6.0 centimetres on east, north and up directions respectively. KEYWORDS: GPS and GLONASS integration; Network-based RTK; Inter-Channel Bias; Ambiguity Resolution.
Latest Advancements in Network RTK Positioning Nicholas Talbot Research Fellow/Trimble Navigation/Australia Phone: +61 (0)3 9518 7464; Fax: +61 (0)3 9518 7401 email@example.com Rodrigo Leandro, Herbert Landau, Markus Brandl, Xiaoming Chen, Alois Deking, Kendall Ferguson, Markus Glocker, Victor Gomez, Adrian Kipka, Gang Lu, Markus Nitschke, Stephan Seeger, Ralf Stolz, Mohamed Ben Tahar, Feipeng Zhang Trimble Terrasat/Germany Phone: +49 8102 7433 0; Fax: +49 8102 7433 131 Since the release of the first commercial GPS Real-Time Kinematic (RTK) products in 1993, the technology has found wide application in many areas including: machine control, construction, precision farming & surveying. Existing RTK systems provide centimetre-accurate positioning typically with initialization times of seconds. One of the main limitations of RTK positioning is the reliance on nearby reference station and data link infrastructure. For single-base and network RTK positioning, the rover normally has to operate within say 100km of the nearest station. Researchers have advocated Precise Point Positioning (PPP) techniques as an alternative to existing RTK methods. With the PPP approach, GNSS positioning is performed using globally determined precise satellite orbit and clock information supplied to users. The published PPP solutions typically provide position accuracies of better than 10cm horizontally. The major disadvantage of PPP techniques is the long initialization needed to converge to sub-decimeter level accuracy. A new approach is presented that finally brings together the advantages of both PPP, and Network RTK positioning. The new positioning techniques deliver centimetre-level horizontal positioning with typically subminute initialization times. The new system operates without a dense reference station network. Details are provided on the performance and capabilities of the new techniques as well as the technical innovations applied in the server software, GNSS correction data transmission format and rover processing algorithms. KEYWORDS: Network RTK, PPP
GPS/Other Sensor Integration (2)
1340 - 1500
Study on the Availability of Vector Tracking Loop in Outdoor Field for GPS and Pseudolite System Sanghoon Jeon Mechanical and Aerospace Engineering, and the Institute of Advanced Aerospace Technology/Seoul National University/South Korea +82-2-880-7545(phone), +82-2-878-8918(fax), firstname.lastname@example.org Hyoungmin So rd The 3 R&D institute / Agency for Defense Development/South Korea +82-10-9147-1905(phone), +82-2-878-8918(fax), Hyuongmin.email@example.com Chongwon Kim Mechanical and Aerospace Engineering /Seoul National University/South Korea +82-2-880-7545(phone), +82-2-878-8918(fax), firstname.lastname@example.org Taikjin Lee Sensor System Center/Seoul National University/South Korea +82-2-958-5717(phone), +82-2-958-5709(fax), Taikjin@kist.re.kr Ghangho Kim Mechanical and Aerospace Engineering /Seoul National University/South Korea +82-2-880-7545(phone), +82-2-878-8918(fax), email@example.com Ho Yun Mechanical and Aerospace Engineering /Seoul National University/South Korea +82-2-880-7395(phone), +82-2-878-0559(fax), firstname.lastname@example.org Changdon Kee Mechanical and Aerospace Engineering/Seoul National University/South Korea +82-2-880-1912(phone), +82-2-888-2069(fax), email@example.com This paper presents the implementation and outdoor field test results of vector-based signal tracking
algorithm designed for GPS and pseudolite (PL) navigation system. To implement the GPS-PL system to field, one of the most severe problems in the use of PL is the near-far problem. If the vector-based tracking loop, known as vector delay/frequency lock loop (VDFLL) algorithm, is applied to GPS-PL system, the nearfar problem could be reduced because the tracking performances for low and instantaneous low C/N0 signal are enhanced. To study on the tracking performance of vector tracking loop implementation for GPS and PL system, we have accomplished two tests using GNSS software defined radio. One is the analysis of the improvement of tracking and navigation performance in GPS shadow area. In the test a user moves away to the far zone from working area, the receiver cannot keep tracking PL signal in the conventional independent tracking loop. In VDFLL, however, the receiver successfully estimates the signal and succeeds to track the weak PL signal. In addition to the far zone test, we tested the near zone tracking performance. When a user comes into the near zone, the majority of GPS and other PL signals are disrupted by relatively strong PL signal. In this situation, the implemented VDFLL tracks GPS signals continuously. Therefore the coverage of the GPSPL system with VDFLL implementation became wide, compared with the conventional independent tracking loop. From the test results, the availability of the use of GPS and PL system are analysed. KEYWORDS: Vector tracking loop, Pseudolite, VDFLL, Software Defined Radio
Comparing the Mathematical Models for GPS & GLONASS Integration Tao Li The University of New South Wales, Sydney, Australia +61-(0)2-0430882278, firstname.lastname@example.org Jinling Wang The University of New South Wales, Sydney, Australia +61-(0)2-93854203, email@example.com GPS has been successfully used in surveying and navigation applications for many years, but there are still some scenarios with few satellites available, and such a poor condition cannot guarantee the positioning accuracy. However, with the increasing number of available GLONASS satellites, an integration of GPS&GLONASS will be of great interest for the successful integer ambiguity resolution, since the satellite geometry and the reliability will be greatly improved. The problem with GLONASS satellites is that the frequencies vary with different satellite PRN, which then results in a complexity in the mathematical models when handling the integer ambiguity issues. For the past several decades, many literatures have discussed the mathematical models for GPS&GLONASS integration, and several models have been proposed. In this contribution, a comprehensive study of mathematical models for GPS&GLONASS integration is given. Firstly, the current mathematical models for integration are studied, with some discussions on their advantages and disadvantages in data processing. Then, real GPS&GLONASS data sets are processed with different mathematical models, and in order to evaluate their performances according to ambiguity resolution, several model quality measures such as the success-rate, ADOP, ratio-test values are presented and analysed. In the end, conclusions are given on which mathematical model is the most suitable one to use. KEYWORDS: GPS&GLONASS, functional model, ambiguity resolution, ambiguity validation
Preciser Positioning and Timing with the Measured Time Offset Nathan L. Knight School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Tel: +61-2-9385 4185 Fax: +61-2-9313 7493 Email: firstname.lastname@example.org Jinling Wang School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Tel: +61-2-9385 4203 Fax: +61-2-9313 7493 Email: email@example.com With the development of numerous satellite navigation systems, there has been growing interest in the development of system independent receivers. However, one of the problems encountered is in the different time systems employed by each of the satellite navigation systems. Consequently, it has become standard practice to solve for the time differences within the receiverâ€&#x;s navigation solution. However, there are several ways of solving for the time differences and some doubt exists about their equivalence. Nevertheless to enhance interoperability and to enable a position to be obtained with any four satellites, satellite navigation system providers are intending to measure and transmit the time offsets to other time systems. The broadcast time offsets though are imprecise and cannot be applied as error less corrections. Consequently, numerous methods of employing the broadcast time offsets have been developed that account for their imprecision. While it is clear that the measured time offsets should be employed when a position would otherwise not be obtained, there is doubt surrounding whether or not the broadcast time offsets should always be employed. Hence, this paper initially proves that a number of methods of solving for the time differences are mathematically equivalent. Likewise, it is also proven that a number of the methods of accounting for the time differences with the broadcast time offsets are mathematically equivalent. Finally, it is proven that preciser position and time estimates, and smaller DOPs, are obtained with the broadcast time offset. KEYWORDS: GNSS, Single Point Positioning, GGTO, Precision.
GPS/MEMS IMU Integration System Design for Car Black Box Moon Suk Koo (1) Department of Electronics Engineering/Chungnam National University/South Korea Phone: 42-821-7709, email: firstname.lastname@example.org Hyun-min Ji (2) Department of Electronics Engineering/Chungnam National University/South Korea Phone: 42-821-7709, email: email@example.com Sang Heon Oh (3) Integrated Navigation Division/Hanyang Navicom Co Ltd./South Korea Phone: 42-363-9249, email: firstname.lastname@example.org Dong-Hwan Hwang (4) Department of Electronics Engineering/Chungnam National University/South Korea Phone: 42-821-5670, email: email@example.com The car black box record data of the situation when an accident occurs and it used to investigate cause of the accident. The car black box records image data, operating status attached devices and positioning of the car. In order to provide position and velocity to the car black box, a navigation system is required. The GPS receiver has been used as a navigation system for the car black box. However the GPS receiver cannot provide the navigation information when satellite signals are blocked. In order to avoid this problem, the GPS receiver can be integrated other sensors. In this paper, an integrated navigation system, in which a GPS receiver is combined with a MEMS(micro electro mechanical systems) based IMU(Inertial Measurement Unit) is designed. An error model is which the characteristics of the MEMS IMU are considered is derived and Kalman filter is design. The effective of the designed navigation system was shown through experimental results. KEYWORDS: MEMS IMU, GPS, Sensor Integration, Car Black box
1340 - 1500
Development of a GNSS Software Receiver Platform Jinghui Wu School of Surveying & Spatial Information Systems, University of New South Wales, Australia Ph: +61(2)93854206 / Fax: +61 (2) 9313 7493/ email: firstname.lastname@example.org Nagaraj C. Shivaramaiah School of Surveying & Spatial Information Systems, University of New South Wales, Australia Ph: +61 (2) 9385 4185 / Fax: +61 (2) 9313 7493/ email: email@example.com Andrew Dempster School of Surveying & Spatial Information Systems, University of New South Wales, Australia Ph: +61 (2) 9385 6890/ Fax: +61 (2) 9313 7493/ email: firstname.lastname@example.org
Multi-GNSS receivers are rapidly making their way into the mainstream of navigation and positioning technology. Global Navigation Satellite System (GNSS) users, especially those in Australia, will benefit from the utilisation of not only the United State‟s modernised GPS but also of Europe‟s developing Galileo, China‟s Compass and Russia‟s modernised GLONASS systems. Development for multi-GNSS applications requires the support of a flexible end-to-end receiver platform. This paper discusses the development of a Matlab based multi-GNSS software receiver platform with the ability to process the existing GPS L1 C/A, Galileo GIOVE E1 and GLONASS L1 signals and the future Galileo E1 open service signal. In addition this paper will also provide the acquisition, tracking and positioning performance verification results for the tests using a simulator (Spirent) as well as real signals where available (e.g. the raw digitised Intermediate Frequency data collected from a Radio Frequency frontend). KEYWORDS: GNSS, Software Receiver, Galileo, GPS, GLONASS
The Witch Navigator - A Software GNSS Receiver for Education and Research Pavel Kovář Czech Technical University in Prague/Czech Republic +420 2 2435 2244, email@example.com Petr Kačmařík Czech Technical University in Prague/Czech Republic +420 2 2435 2258, firstname.lastname@example.org Ondřej Jakubov Czech Technical University in Prague/Czech Republic +420 2 2435 2268, email@example.com František Vejražka Czech Technical University in Prague/Czech Republic +420 2 2435 2246, firstname.lastname@example.org The paper introduces the Witch Navigator, which is an ExpressCard form factor software GNSS receiver for a notebook or a personal computer, developed for educational and research purposes. The signal processing runs on a FPGA and a PC processor, the mutual communication is realized via a PCI Express bus. The receiver is equipped with two reconfigurable front ends. The complex multi-antenna, multifrequency and multi-constellation GNSS system can be built by interconnecting several receiver cards by a special connector. The receiver can operate in a classical mode with hardware GNSS correlators which are programmed into the FPGA, or in a pure processor mode in which the PC processor directly processes signal samples measured by the receiver in real time. For the processing of most of the GNSS signals, the universal GNSS correlator has been developed and tested. The FPGA signal processor is equipped with a signal capture unit for the measurement of the signal snapshots for the DSP signal acquisition in the PC. The processing of the extremely wideband GNSS signals (Galileo E5) is realizable by a special method the performance of which is only slightly poorer than the performance of the optimum receiver, while the hardware complexity is a quarter of the optimum one. KEYWORDS: Software GNSS receiver, Galileo E5, ExpressCard, GNSS correlator
Design of a Correlator using GPU for Real-time GNSS SDRs Sang Wook Hwang (1) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Seong Han Cho (2) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Chansik Park (3) Department of Electronics Engineering/Chungbuk National University/Korea email@example.com Sang Jeong Lee (4) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org With the advent of multiple GNSS such as GPS, GALILEO, GLONASS and so on, the diversity of signals to be received increases. A flexible receiver is required to receive these signals and to develop new ideas efficiently. SDR(Software-Defined Radio) is one of the most effective solutions due to intrinsic flexibility and scalability. Lots of research has been done for developing a real-time SDR with FPGA, DSP or general purpose microprocessors. This paper focuses on the correlator implementation for GPS L1 receiver. It proposes a new correlator architecture for real-time SDRs. To meet real-time requirements, the correlators are implemented using the GPU from NDIVIA CUDA technology. All arithmetic functions will be implemented with GPU. The proposed GPU based correlator will be implemented and the processing load and time are evaluated using the implemented correlator. KEYWORDS: GNSS, GPS L1 Receiver, Real-time SDR, GPU Correlator
High-Precision GPU (Graphic Processing Unit)-Based Software-Defined Real-time GNSS Signal Monitoring Receiver Sung-Hyuck Im A Department of Information and Electronics Engineering/Konkuk University/KOREA 02-452-7407 & 02-3437-5235 Gyu-In Jee A Department of Information and Electronics Engineering/Konkuk University/KOREA 02-450-3070 & 02-3437-5235 Recently, software GNSS receiver is the attractive issue in navigation application part. Such software implementations can be easily adopted to handle new signals and allow for rapid testing of developed algorithms. Moreover, for signal monitoring use, a flexibility of the software receiver is needed. Although modern CPUs are more and more evolving to multi-core processors, the performance from a single chip is usually not sufficient to fulfill the needs of real-time GNSS signal processing. On the other hand, Graphic Processing Unit (GPU) has undergone a tremendous development in the recent years and deployed electronic components have become powerful parallel systems, which can be utilized for a variety of applications. In this paper, we implemented the software-defined high-precision monitoring GNSS receiver using GPU. A 40MHz-sampled intermediate frequency (IF) signal is acquired and tracked in real-time. In the case of using a NVIDIA C2050, The implemented receiver can track the 12 channels. Each channel has the 48-tap code delay (variable code delay) outputs. For the real-time implementation of the massive correlators, a modified reduction technique was proposed and strategic use of memory such as a register, a constant memory, and a global memory was considered. Additionally, a spectral characteristic of the IF signal can be monitored. Finally, we implemented a GPU-enabled software GNSS signal monitoring system. The organized system consisted of A RF front-end, a 8-bit digitizer, two NVIDIA C2050, and a workstation. The system can process the dual-frequency signals in real-time. For the evaluation, we compared the developed system with Novatel OEMV-3. KEYWORDS: GPU, GNSS, Software receiver, Signal Monitoring
Vehicle Positioning Proudly sponsored by Position Partners
1340 â€“ 1500
GNSS Uptake in Agriculture - Applications and Barriers Dr Don Yule CTF Solutions, Australia +61 7 38710359 email@example.com Dr Phil Collier CRC for Spatial Information, Australia +61 3 8344 8125 firstname.lastname@example.org The adoption of precise positioning technologies based on GNSS for spatially enabled cropping systems (e.g. controlled traffic farming (CTF) is about 15%. We undertook a focussed study to identify current adoption of precise positioning and CTF, and the major barriers to the adoption of NRTK technologies for CTF. Our aims were to validate the assumption that genuine and remediable barriers to adoption exist and to provide a foundation for subsequently enhancing national adoption rates. We used three case studies in the Wimmera region of Victoria, central west NSW and Fitzroy in Queensland, involving regional surveys of the grain growing community and the precise positioning service providers. Questionnaires addressed detailed current adoption of practices and technologies, future plans, and perceived barriers across all people surveyed. From survey data analyses we will propose further actions, particularly ways to address the barriers. KEYWORDS: Precise positioning, agriculture, regional applications.
Studies of Effects of Wireless Communication on GNSS Positioning Performance in High-mobility Vehicle Environment Ming Qu Queensland University of Technology, Brisbane, Australia 0430810289, email@example.com Yanming Feng Queensland University of Technology, Brisbane, Australia firstname.lastname@example.org Charles Wang Queensland University of Technology, Brisbane, Australia email@example.com In order to support Intelligent Transportation System (ITS) road safety applications, such as collision avoidance, lane departure warnings and lane keeping, Global Navigation Satellite System (GNSS)-based vehicle positioning system has to provide lane-level accurate and reliable positioning information to vehicle users. However, current vehicle navigation systems equipped with a single frequency GPS receiver can only provide road-level accuracy at 5-10 meters. The positioning accuracy can be improved with the augmented GNSS techniques such as Real Time Kinematic (RTK) and Precise Point Positioning (PPP) which have been traditionally used in land surveying and or in slowly moving environment. In these techniques, GNSS corrections data generated from a ground reference network are broadcast to road users via various communication data links, particularly 3G cellular networks. In this research effort, we will examine the performance of 3G data transmission in the high mobility vehicle environment and the potential effects on the positioning performance using RTK and PPP positioning techniques. The mobile network performance will be analysed in terms of packet transmission latency, mobile station handover delay, quality of mobile signals. Experiments will be conducted on the highway between Brisbane CBD to Beenleigh. Two different types of receivers, CHC and Trimble RTK systems are used in the experiments. The receivers are connected to the SUNPOZ data server for correction services via Telstra 3G and Optus 3 G modem respectively. Preliminary experimental results have shown the data drops frequently occur for 1 -5 seconds over the testing route, which indeed affect the onboard RTK solutions with both receivers significantly, while operation in the static environments experienced occasional packet drops of 1 or 2 seconds. As the communication link performance has been least understood or assumed to have no significant impact on the positioning accuracy in the low mobility environment, this research could be meaningful step in addressing ITS safety challenges, for which vehicle to vehicle and vehicle to infrastructure communications and precise vehicle positioning are two key enabling technologies.
Key words: Road safety, RTK, PPP, 3G cellular networks, high mobility vehicle
A Particle Filter Based State Estimation of Semitrailer Vehicle for Jackknifing Prevention Hee Won Kang (1) Satellite Navigation Department/Korea Aerospace Research Institute/Korea firstname.lastname@example.org Sebum Chun (2) Satellite Navigation Department/Korea Aerospace Research Institute/Korea email@example.com Moon-Beom Heo (3) Satellite Navigation Department/Korea Aerospace Research Institute/Korea firstname.lastname@example.org The transportation by semitrailer vehicles has increased nowadays as the demand and supply for land-cargo transportations has grown up, because those depend significantly upon a semitrailer vehicle. A semitrailer vehicle with an articulated structure of 2-bodies is composed with a tractor and a trailer. It has the benefit that road restrictions are less than that of a rigid body vehicle. Unlike general vehicles with 1-body, but, a jackknifing accident can happen for tractor or trailer spins due to an articulated structure. To prevent a jackknifing accident, self-control techniques have been applied to semitrailer vehicles before the manufactory stage because the sensors those are used for estimating vehicle states are located inside the vehicle. In order to overcome such limit, this paper proposes a method which estimates states of the semitrailer vehicle by using a GPS receiver without sensors equipped in the vehicle has been proposed. States of vehicle is estimated by using a particle filter. And the states estimation could be done if the system model was not a linearized dynamic model and the noise did not have a White-Gaussian distribution. By simulation results, it has been confirmed that the proposed method can predict jackknifing accident properly. And the success rate of carrier ambiguity fixing has been grown by using the dynamic model of the semitrailer vehicle used for the particle filer. In order to evaluate the performance of proposed method, measurements were generated by using GPS simulator. In the future, it can be expected that the results of this paper would contribute to decrease accidents of a semitrailer vehicle as the basic method for after-market products of safe driving. KEYWORDS: Jackknifing Prevention, Paricle Filter, State Estimation, Carrier Ambiguity Fixing.
Inertial-Aided Visual Odometry for Automotive Applications Nicola Mosca (1) Barbara Hardy Institute/University of South Australia/South Australia Phone: +61 8 8302 2361, Fax: +61 8 8302 1880, email@example.com Ettore Stella (2) Institute of Intelligent Systems for Automation/CNR/Italy Phone: +39 080 5929 426, Fax: + 39 080 5929 460, firstname.lastname@example.org Rocco Zito (3) Barbara Hardy Institute/University of South Australia/South Australia Phone: +61 8 8302 1863, Fax: +61 8 8302 1880, email@example.com Accurate and reliable positioning systems, also known as Automatic Vehicle Location (AVL) systems, enable fleet management systems to achieve better planning and scheduling outcomes. However GPS based AVL systems, or loosely coupled GPS/INS systems, do not provide reliable positioning in particular conditions, such as under tunnels or in â€œcity canyonsâ€?. In this paper we present a loosely coupled low-cost GPS/INS-aided visual odometry positioning system to be employed in automotive applications. The system is designed to primarily rely on the GPS/INS subsystem during normal operations while providing a fallback strategy to provide positioning information in GPS denied environments. In this situation, while GPS cannot be used to correct the MEMS accelerometers, the angular information available from the gyroscope, ie the rotations around the perpendicular axis, can be used as a first approximation to aid the visual odometry system to filter out outliers in frame-to-frame matching algorithms implemented. The paper presents the method and experimentally compares the impact of vision systems to supplement traditional GNSS solutions inside and outside GPS denied environments. The results of the methodology used are quite encouraging and so much promise for use in a number of position critical applications of AVL.
KEYWORDS: AVL, GPS/INS, visual odometry.
CORS - Regional to Global Proudly Sponsored by Position Partners
1530 - 1710
Positional Stability Study of Continuously Operating Reference Stations: Case Study of Tianjin CORS Xu Ying (1) College of Environmental & Resource Sciences, Fujian Agriculture & Forestry University, 350002, China; Research Center of GNSS, Wuhan University, 430079, China; 86+15280088261; Email Address: firstname.lastname@example.org Liu hui (2) Research Centre of GNSS, Wuhan University, 430089，Wuhan, China Email Address: email@example.com BERNESE 5.0 Software was adopted in this paper to calculate the data observed by TJCORS of 2007-2009 in Tianjin region to obtain the reference station coordinate time series. Then the composition stability of TJCORS reference stations is discussed. The result indicates that the whole TJCORS frame has the movement tendency of S-E-E direction horizontally. In the altitude direction, the annual settlement values in CH01 and SW01 are larger, but there are almost no settlement emerging in reference stations of CH02, JIXN and TJA1 that are located in the north part of Tianjin. The calculation results of TJCORS are compared with the settlement contour isogram of 2006 and level survey velocity of 2007-2009. The comparisons show that the ground settlement values and settlement funnel distribution are relatively continent. Furthermore, the result indicates that the treatment of ground settlement in Tianjin region has been proved to be effective in recent years, but new settlement funnels have appeared in some districts. KEYWORDS: TJCORS, BERNESE Software, reference station coordinate time series, ground settlement
Assessment of Network RTK Performance using CORSnet-NSW Volker Janssen Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services, Bathurst NSW 2795, Australia Tel: +61-2-6332 8426, Fax: +61-2-6332 8479, Email: Volker.Janssen@lpi.nsw.gov.au Joel Haasdyk Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services, Bathurst NSW 2795, Australia Tel: +61-2-6332 8485, Fax: +61-2-6332 8479, Email: Joel.Haasdyk@lpi.nsw.gov.au CORSnet-NSW is a rapidly growing network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) providing fundamental positioning infrastructure for New South Wales (NSW) that is accurate, reliable and easy to use. This positioning infrastructure supports a wide range of GNSS applications in areas such as surveying, agriculture, mining and construction. This paper briefly outlines the difference between the traditional, single-base Real Time Kinematic (RTK) and the Network RTK (NRTK) approaches. It continues to report on extensive testing carried out at several locations in eastern NSW to investigate the performance of the CORSnet-NSW NRTK service outside the Sydney metropolitan area, and with larger inter-CORS distances than those found in Sydney (25 km on average). Comparisons are made between NRTK and single-base RTK operation over varying distances to illustrate the performance of NRTK in the study areas. The achievable precision was investigated over multiple days at four different locations, while the achievable accuracy was determined by comparison to the State‟s survey ground control network over several days in seven test areas exhibiting a range of NRTK scenarios and cell sizes. These tests have shown that while NRTK has the same „look and feel‟ as single-base RTK, it produces superior coordinate results in regards to both precision and accuracy. The benefit of averaging observations over a window of 1-2 minutes and re-occupying points 10-30 minutes later is illustrated. It is also shown that coordinate quality (CQ) indicators provided by the GNSS rover equipment are often overly optimistic, even under the favourable satellite visibility and multipath conditions encountered during our tests, and should therefore be used with caution. .
An Overview on RTK Network of Turkish Republic (TUSAGA-Aktif) Cetin Mekik Karaelmas University, Engineering Faculty, Dept. of Geodesy and Photogrammetry Eng., Zonguldak, Turkey, e-mail: firstname.lastname@example.org Omer Yildirim Gaziosmanpasa University, Engineering Faculty, Dept. of Geomatics Eng., Tokat, Turkey, email: email@example.com Sedat Bakici General Directorate of Geographical Information Systems, General Director, Ankara, Turkey, email: firstname.lastname@example.org Basically Real Time Kinematic GPS Network (RTK Network) consists of continuously operating GPS/GNSS stations and a control centre which computes and transmits RTK corrections tor the receivers of users in the field. Hence, no post-processing involved. These RTK corrections generated by the network, so-called Network RTK, are used to determine three dimensional positions of rovers instantaneously with cm accuracies. These networks have been operating in many countries all over the world since the beginning of 2000s. This paper gives the infrastructure of the Turkish RTK CORS Network called TUSAGA-Aktif established by Istanbul Kultur University in association with the General Directorate of Land Registration and Cadastre and the General Command of Mapping and sponsored by the Turkish Scientific and Technical Research Agency (TUBITAK). The network constitutes 146 Continuously Operating Reference Stations controlled by the two control stations, the Master Control Station at the Geomatics Department of the General Directorate of Land Registration and Cadastre and the Auxiliary Control Station at the Headquarters of the General Command of Mapping both in Ankara, the capital city of Turkey. In this paper some results obtained from a test is also given for the evaluation of the network performance and the number of users from the early stages of the system. KEYWORDS Network RTK, GNSS, TUSAGA-Aktif, Control Stations, RTK Corrections.
AllDayRTK - A National CORS Network for Australia Gavin Docherty UNSW/Position Partners/Australia Ph: 61-0400 354 873 email: email@example.com Martin Nix UNSW/Position Partners/Australia Ph: 61-0437 013 747 email: firstname.lastname@example.org During a time of significant development in Australian CORS infrastructure, AllDayRTK is emerging as one of the first truly National real time positioning services with infrastructure partnerships across both the commercial and Government sectors. AllDayRTK is a network of continuously operating GNSS reference stations which consists of CORS that are either fully owned by Position Partners or by one of the Position Partnersâ€&#x; data sharing associates. The AllDayRTK network provides Network RTK, RTK and DGPS corrections to a number of industry sectors. One of the main user groups that are moving towards the network RTK service provided by AllDayRTK is the precision Agriculture industry. The main driver for this shift to precise positioning is a relatively new technique called inter-row sowing. Inter-row sowing is a technique used by farmers to maximise crop yields by sowing new crops in between existing crop rows to minimise soil born diseases and negates the need for farmers to clear crop stubbles from previous harvests [The Allen Consulting Group â€“ Final report]. The efficiency of this technique provides a multitude of benefits at times of uncertain weather cycles in remote regional areas and will almost certainly be necessary in the future . The AllDayRTK network has been the subject of comprehensive height testing in Melbourne (Victoria) where it has been benchmarked alongside the existing VicPos and checkpoint networks. The testing of the network has been carried out by PHD students from The University of Melbourne and is being used to determine the level of density for CORS networks to provide accurate heights to height sensitive end users. As part of this height testing, ionospheric activity has been considered as this is expected to have an impact on the performance of spatial services during solar peak periods.
KEYWORDS: CORS, AllDayRTK, Inter-row sowing, Solar Cycle, Network RTK
The Practicalities of Running CORS Based Services â€“ a SmartNet Perspective Aaron Jordan SmartNet Aus Ph +61 (0) 407 457 346 Fx +61 (0) 7 3891 9336 email@example.com Mark Burbidge SmartNet Europe Ph +44 (0)1293 888513 firstname.lastname@example.org SmartNet is a Leica Geosystems initiative to provide GNSS CORS based services to multiple market segments including Surveying, Precision Agriculture and GIS. SmartNet began in the UK back in 2006 and five years later SmartNet is available in many countries through Europe, North America and Australia. Unlike other CORS papers, this paper will focus on the practicalities of running a CORS based service rather than the GNSS technology itself. Drawing from our own experiences, three broad topics are discussed; (1) what it takes to keep a service running 24/7 and meeting customer expectations; (2) the issues around building CORS networks based on shared infrastructure and managing coordinates of the reference stations; and (3) the challenges of bringing GNSS CORS based services to the market through various business models, sales and support channels, and competition. The aim of this paper is to momentarily take the focus away from resolving integer ambiguities and to instead provide an insight into the practicalities of delivering commercial GNSS services, as there is much more than meets the eye. KEYWORDS: CORS, SmartNet, Services, GNSS, RTK
GPS / Inertial Integration
1530 - 1710
Enhanced RTK-GPS with IMU and Vehicle Sensors in Urban Environment Dihan Chen (1) Tokyo University of Marine Science and Technology, Japan Phone & Fax: (81)03-5245-7376 email address: email@example.com Nobuaki Kubo (2) Tokyo University of Marine Science and Technology, Japan Phone & Fax: (81)03-5245-7376 email address: firstname.lastname@example.org The increasing demand for navigation and automation has led to the development of a number of accurate and precise GPS (Global Positioning System) applications. Especially in urban environments, GPS multipath can easily lead to fixed position errors of over 1 m owing to wrong integer ambiguity. This paper presents a method to improve the RTK-GPS (real-time kinematic GPS) using a low-cost IMU (inertial measurement unit) and normal vehicle sensors for applications in urban environments. The popular LAMBDA method and the ratio test were used to obtain the fix positions, to use the speed information obtained from Doppler measurements as an alternative, and to use the IMU and vehicle speed sensorsâ€&#x; information (integrated with the RTK-GPS via a Kalman Filter) during the outage of visible satellites. We also used the IMU and vehicle speed sensors to detect the wrong fixes in the RTK-GPS. We performed an experiment in an urban environment in the centre of Nagoya, Japan, which has the longest satellite outage of over 100 s. The POSLV (Applanix) was used to estimate the reference positions. By using our proposed method, most of the wrong fixes could be detected and the standard deviation of the horizontal errors was reduced from 3.03 m to 0.73 m in the total epochs, and the number of epochs where the errors were below 1 m was increased from 30.37% to 65.49% of the total. During GPS outage, it is important to determine the accuracy of the direction of the last car for precise navigation. In this paper, it has been found that the threshold of the maximum HDOP (horizontal dilution of precision) should be set to a low value and a suitable measurement quality check is required to obtain a better direction. These results demonstrate that to some extent, our proposed method is beneficial as an alternative to the normal RTK-GPS in an urban environment. KEYWORDS: RTK-GPS, Doppler measurement, IMU, Vehicle sensors.
A Novel Design for the Ultra-tightly Coupled GPS/INS Navigation Systems Dah-Jing Jwo email@example.com Department of Communications, Navigation and Control Engineering National Taiwan Ocean University, Keelung, Taiwan Chi-Fan Yang firstname.lastname@example.org Department of Communications, Navigation and Control Engineering National Taiwan Ocean University, Keelung, Taiwan Kun-Chieh Lin email@example.com AcBel Polytech, Inc., Tamsui Dist., New Taipei City, Taiwan This paper presents a sensor fusion method for the ultra-tightly coupled (UTC) GPS/INS integrated navigation. The UTC structure, also known as the deep integration, has many advantages, e.g., disturbance and multipath rejection capability, improved tracking capability for dynamic scenarios and weak signals, and reduction of acquisition time. This architecture involves the integration of I and Q (in-phase and quadrature) components from the correlator of a GPS receiver with the INS data. The particles filter (PF) exhibits superior performance as compared to EKF and UKF in state estimation for the nonlinear, non-Gaussian system. To handle the problem of heavy-tailed probability distribution, one of the strategies is to incorporate the UKF into the PF as the proposal distribution, leading to the unscented particle filter (UPF). The combination of adaptive unscented particle filter (UPF) and Fuzzy Logic Adaptive System (FLAS) is adopted for reducing the number of particles with sufficiently good results. The tracking performance is a concern in complex environments such as dynamic scenarios, indoor environments, and urban areas, etc., where the GPS tracking loops may lose lock due to the signals being weak, subjected to excessive dynamics or completely blocked. One of the principal advantages of the UTC structure is that a Doppler frequency derived from the INS is integrated with the baseband loops to improve the tracking capability of the receiver. The Doppler frequency shift will be calculated and fed to the GPS tracking loops for elimination of the effect of stochastic errors caused by the Doppler frequency. Performance assessment for various methods, such as EKF, UKF, UPF and FLAS assisted UPF (FUPF), are carried out. The FUPF algorithm with Doppler velocity aiding demonstrates remarkable improvement in navigation estimation accuracy with reduction of number of particles. KEYWORDS: GPS/INS, Ultra-tightly coupled, Unscented particle filter, Fuzzy logic, Doppler frequency estimation.
Analysis of Outlier Separability in Integrated GPS/INS Systems Ali Almagbile The University of New South Wales, Sydney, Australia +61-(0)2-0430882278, firstname.lastname@example.org Jinling Wang The university of New South Wales, Sydney, Australia +61-(0)2-93854203, email@example.com Weidong Ding The university of New South Wales, Sydney, Australia +61-(0)2-93854208, firstname.lastname@example.org A number of quality control approaches have been employed for outlier detection and identification in either sensor level or integration level. In integration level, the principles of least squares (snapshot) have been implemented by using Kalman filter as least squares technique. In this technique, the measurements and predicted states of Kalman filter are integrated to form the least squares observations vector. In this paper, Kalman filter as least squares is used to investigate the performance of outlier separability measures in tightly coupled GPS/INS integration system. The separability measures have been evaluated based on correlation coefficients between outlier tests statistics. The performance of outlier separability under different number of visible satellite and different number of Kalman filter states for both pseudo-range and timedifferenced carrier phase observations is evaluated. The results show that the performance of separability measures for GPS measurements and dynamic model/ GPS measurements simultaneously is more effective than those for dynamic model only. KEYWORDS: GPS, INS, Integration, Integrity Monitoring, Outlier detection & separation
A Regularized Robust Filter for Satellite Attitude Determination System with Relative Installation Error of Sensor Tracker Jiongqi Wang Department of Mathematics and System Science/National University of Defense Technology/China Phone & Fax 86-731-84573260 Haiyin Zhou Department of Mathematics and System Science/National University of Defense Technology/China Phone & Fax 86-731-84573260 Xiaogang Pan Department of Mathematics and System Science/National University of Defense Technology/China Phone & Fax 86-731-84573260 Yuanyuan Jiao Department of Mathematics and System Science/National University of Defense Technology/China Phone & Fax 86-731-84573260 As one of the most critical issues for high precise satellite attitude determination, the relative installation error of sensor tracker will lead to inconsistent for attitude information. An approach named regularized robust filter algorithm is proposed, which is suitable to control the effect of relative installation error on the attitude determination precision. In the proposed approach, based on the constructed uncertainty model for attitude measuring system, the weighting least square solution is advanced and the regularized robust filter is deduced at fist. And then algorithm parameters are optimized based on the design index, which is to minimize the upper for estimation error variance. Different from the traditional Kalman filter, the regularized robust filter takes the effect of model uncertainty during its design stage, which can be used to optimize the filter parameters design. Thus, the information included in the system model and measuring data can be applied well. And moreover, the existence condition need not be validated in the proposed filter algorithm, which is convenient for online application. To validate the proposed approach, the synthetic attitude data are adopted to test its performance. The test results have demonstrated it provides effective performance to control the relative installation error of star tracker. KEYWORDS: Attitude determination, Regularized robust filter, Sensor tracker, Relative installation error, Precision analysis
Influence of Maneuvers on the Observability of INS/GPS Initial Alignment Xiaosu Xu Southeast University, Nanjing, 210096, China +8625-83793922, email@example.com Yao Li Southeast University, Nanjing, 210096, China +8625-83793922, firstname.lastname@example.org Hong Fang Southeast University, Nanjing, 210096, China +8625-83793912, email@example.com Initial alignment of INS/GPS integrated navigation systems are often realized through some form of Kalman filter. The accuracy and convergence rate of a Kalman filter designed to estimate the system states, which determined by the observability of system states, will affect the accuracy and the time of alignment. As the system matrix is related to the type of maneuvers, the different maneuvers may cause the change of system observability. Therefore, it has very important significance for initial alignment to analyze the influence of maneuvers on the observability of system states and find out the way to improve the observability of system. In this paper, the degree of system observability is analyzed. We consider three types of maneuvers, the linear motion, angular motion, linear and angular motion. The simulation results show that the angular motion is more effective to improve the accuracy and speed of alignment since the observability is improved.
KEYWORDS: INS; GPS; maneuver; in-motion alignment; observability.
Cooperative Vehicle Positioning
1530 - 1710
A Cooperative Positioning Method for VANETs using DSRC Carrier Frequency Offset Nima Alam University of New South Wales, Sydney, Australia Ph: +61 2 9385 4174, Fax: +61 2 9313 7493, firstname.lastname@example.org Asghar Tabatabaei Balaei University of New South Wales, Sydney, Australia Ph: +61 2 93854050, Fax: +61 2 9385 5993, email@example.com Andrew G Dempster University of New South Wales, Sydney, Australia Ph: +61 2 9385 6890, Fax: +61 2 9313 7493, firstname.lastname@example.org Vehicular positioning in urban canyons or covered areas such as car parks is a challenging issue due to the limited availability or lack of Global Navigation Satellite System (GNSS) signals. Tackling this problem, the concept of Cooperative Positioning (CP) has recently emerged for positioning or positioning enhancement in Vehicular Ad hoc Networks (VANETs) based on vehicular communication and range estimates between the vehicle and some reference nodes with known position, anchors, which can be other vehicles or infrastructure nodes. The viability and performance of the conventional radio ranging methods such as Received Signal Strength (RSS), Time of Arrival (TOA), and Time Difference of Arrival (TDOA) for vehicular environments is questionable. Regarding the constraints and shortcomings of radio-ranging methods, a new CP technique is presented. This technique is based on range-rate estimates between the vehicle and infrastructure anchors. Range-rate is estimated using Carrier Frequency Offset (CFO) of the vehicular communication packets. Dedicated Short Range Communication (DSRC) is considered for vehicleinfrastructure communication. The performance of the proposed CP method is evaluated with regard to the speed of the vehicle and CFO noise. It is concluded that, range-rate-based CP is a potential method for CP where the GNSS signal is weak or not available. KEYWORDS: Cooperative Positioning, Carrier Frequency Offset, DSRC, VANET.
Evaluation of a Cooperative Positioning Algorithm by Tight GPS/DSRC Integration for Vehicular Networks Mahmoud Efatmaneshnik School of Surveying & SIS, UNSW, Sydney 2052 Tel: 02 9385 4190, Email: email@example.com Nima Alam School of Surveying & SIS, UNSW, Sydney 2052 Tel: 02 9385 4190, Email: firstname.lastname@example.org Allison Kealy Department of Geomatics, University of Melbourne, Melbourne 3052 Tel: 03 83446804, Email: email@example.com Andrew G. Dempster School of Surveying & SIS, UNSW, Sydney 2052 Ph: 0 2 9385 6890, firstname.lastname@example.org GNSS alone is not a reliable source for DSRC safety applications. Cooperative Positioning (CP) in VANET refers to a technique based on communication via a DSRC channel and information fusion. CP combines the information gathered from several road users to refine self-position. CP can require range measurement between vehicles by some radio ranging technique. Two types of CP are introduced in this paper, loose and tight GPS/DSRC integration, which differ in the type of data being communicated. For loose CP, the position, velocity and measured ranges are broadcast to all neighbouring vehicles. For tight CP, the pseudo-ranges are communicated, instead of the positions. The two algorithms are compared using a Cramar Rao Lower Bound (CRLB) analysis and their effectiveness is evaluated. Tight integration proves to perform better, as might be expected. KEYWORDS: DSRC, Cooperative Positioning, Tight Integration, CRLB, VANET .
Performance Boundaries for Cooperative Positioning in VANETs Nima Alam University of New South Wales, Sydney, Australia Ph: +61 2 9385 4174, Fax: +61 2 9313 7493, email@example.com Asghar Tabatabaei Balaei University of New South Wales, Sydney, Australia Ph: +61 2 93854050, Fax: +61 2 9385 5993, firstname.lastname@example.org Andrew G Dempster University of New South Wales, Sydney, Australia Ph: +61 2 9385 6890, Fax: +61 2 9313 7493, email@example.com The concept of Cooperative Positioning (CP) has emerged recently to improve the quality of positioning in Vehicular Ad Hoc Networks (VANETs). CP is considered either for positioning where the Global Navigation Satellite System (GNSS) is not available or for GNSS-based positioning accuracy improvement. Positioning accuracy enhancement is necessary to meet the requirements of the vehicular position-based applications such as collision avoidance which cannot rely only on GNSS performance. CP systems are based on fusing data from different sources, including GNSS, for positioning quality improvement. A typical class of CP is based on the GNSS-based position estimates and distances between the participating vehicles. Inter-vehicle ranging and GNSS errors are limiting factors for achievable performance using CP systems. Inter-vehicle range-rate is also a potential observable for CP systems. In this article, the performance boundaries for range-based and range-rate-based CP systems are investigated. The limits on the achievable performance with different topologies and observations are investigated. Also, the required bandwidth is considered for evaluating the performance of the discussed CP structures. KEYWORDS: Cooperative Positioning, VANET, CRLB, Ranging, Range-rating.
Next Generation Vehicle Positioning Systems Integrated with Wireless Communications to Address Cooperative ITS Challenges in Australia Yanming Feng Queensland University of Technology, Australia, firstname.lastname@example.org James Millner Department of Sustainability and Environment, Victoria Government, Australia Matt Higgins Department of Environment and Resource Management, Queensland Government, Australia Cooperative-Intelligent Transportation Systems (C-ITS) employs vehicle to infrastructure (V2I) and vehicle to vehicle (V2V) communications to connect transport infrastructures, vehicles and travellers, to make road travel safer, faster, cleaner and more convenient. Simply, a vehicle can share its location information with other vehicles and traffic operation centres which greatly increases the opportunities to apply vehicle positioning technologies for improving road safety. C-ITS is the next big wave of ITS and is gaining increasing momentum internationally. Vehicle positioning and digital road maps are two key enabling technologies, alongside the advanced V2V and V2I wireless communications. This paper provides analysis for vehicle positioning requirements for road safety applications. In general, to support many advanced road safety applications, such as Intersection Collision Warning and lane change warning, the vehicle positioning system has to identify which lane the vehicle with respect to road lane marks on road surface and where in the lane with respect to nearby vehicles. This suggests the requirements for absolute and relative positioning accuracy of 50 to 20 centimetres at the 95 percentile respectively. A review for GNSS-based vehicle positioning technologies and prototype systems and relevant international standards is also presented. The findings clearly indicate that lane-level requirement parameters cannot be fulfilled by GNSS autonomous navigation solutions, even though the multi-GNSS systems are available in the future. Medium-end and highend lane level positioning solutions have been developed and tested in different projects internationally. Various levels of vehicle positioning systems can co-exist and support different grades of safety applications. All the system developers share the general vision for hybrid navigation systems and Real Time Kinematic (RTK) techniques, which combine the potential of GNSS for highest accuracy and on board sensors inside the vehicle to improve the reliability and availability of the positioning function. To serve the vehicle positioning users in Australia, one of the challenges is to make use of the existing national positioning infrastructure to provide real time positioning services of sub-metre to centimetre levels all over the country. The trend is a system that provides corrections for all types for RTK and Precise Point Positioning (PPP) users with single, dual and triple frequency receivers. Another challenge is to provide seamless highprecision position solutions along the road networks in the most cost effective manner. This desires unification of the positioning infrastructure (outdoor) and roadside wireless infrastructure, such as radio beacons and other wireless positioning infrastructure additional ranging signals over the restricted areas.
Potentially, vehicle positioning users could be the biggest professional user group for precise real time positioning services. Lane-level positioning for safety applications presents the biggest ever opportunity for GNSS community, deserving dedicated research and development attentions. Key words: Cooperative-Intelligent Transportation Systems, Dedicated Short-Range Communications (DSRC), Vehicle Positioning and Road safety, Global Navigation Satellite Systems
A Filtering Method for Improving the Precision of Cooperative Positioning in VANETs Nima Alam University of New South Wales, Sydney, Australia Ph: +61 2 9385 4174, Fax: +61 2 9313 7493, email@example.com Asghar Tabatabaei Balaei University of New South Wales, Sydney, Australia Ph: +61 2 93854050, Fax: +61 2 9385 5993, firstname.lastname@example.org Andrew G Dempster University of New South Wales, Sydney, Australia Ph: +61 2 9385 6890, Fax: +61 2 9313 7493, email@example.com Vehicular Cooperative Positioning (CP) is a recently emerged concept to estimate or improve the position information of the vehicles in Vehicular Ad-Hoc Networks (VANETs). Using CP, positioning accuracy and availability is improved in the areas without (or with poor) availability of the Global Navigation Satellite System (GNSS) signals. CP is based on vehicular communication for which Dedicated Short Range Communication (DSRC) is considered as a standard medium. Considering the aspects and constraints of DSRC, participating infrastructure nodes in a CP system must be installed along the streets, especially in the dense urban areas. This geometrical arrangement leads to Dilution of Precision (DOP) issues which have impacts on the performance of a CP technique and generally neglected in the literature. In this article, the effect of such typical geometry on available information for CP is investigated. The DOP for a multilaterationbased CP is analysed and a filtering method for improving the accuracy of the CP is proposed. KEYWORDS: Cooperative Positioning, DSRC, DOP,VANET.
0900 - 1040
GNSS Carrier Phase Ambiguity Resolution Aided by Float Transformation Yang-Zen Chen (1) Department of Civil Engineering/National Central University/Taiwan 886-3-422-9332#57615 firstname.lastname@example.org Joz Wu (2) Center for Space and Remote Sensing Research/National Central University/Taiwan 886-3-422-9332#57626 email@example.com Generally, the Global Navigation Satellite Systems (GNSS) carrier-phase is more accurate than the pseudorange. While using carrier phases for positioning, the key point is how to obtain correct integer ambiguity quickly and efficiently. But ambiguity resolution becomes very difficult because of the high correlation between these integer parameters. One of the traditional ways to solve the problem is using a decorrelation technique. The famous LAMBDA and LLL algorithms are members of the technique. This technique maps the parameters from a higher correlation space to a lower correlation space based on an integer transformation matrix. And then some integer candidates are chosen in the lower-correlation space. Finally, the candidates are transformed back to the original space and compared with each other. This research attempts to generate a float transformation technique. This technique is based on the decorrelation technique. And the proposed method is used to ameliorate a traditional integer transformation. After using the float matrix, the number of ambiguity candidates can be reduced once again. At last, the candidates are inserted into the observation equations to determine the solution again. It is believed that the integer candidate which produces the smallest sum of squares of the residual is the most likely solution we want. KEYWORDS: Integer ambiguity, High correlation, Decorrelation, Float transformation.
Reliability of Partial Ambiguity Resolution with Multi-GNSS Constellations Jun Wang Faculty of Science and Technology Queensland University of Technology, Australia Phone: +61 7 31389111, Fax: +61 7 31389390, Email: firstname.lastname@example.org Yanming Feng Faculty of Science and Technology Queensland University of Technology, Australia Phone: +61 7 31381926, Fax: +61 7 31389390, Email: email@example.com Reliable ambiguity resolution (AR) is important to real-time kinematic (RTK) technique, since incorrect ambiguity fixing can lead to largely biased positioning solutions. The concept of partial ambiguity resolution (PAR) refers to the case where only part of ambiguities can be fixed correctly to their integers in the integer least square estimation system at high success rates. As a result, RTK solutions can be derived from these integer-fixed phase measurements. This is justifiable in the multi-GNSS constellations where use of partially resolved phase measurements would be sufficient for precise RTK solutions. The question is how to achieve reliable PAR in the multi-GNSS environment. In order to improve AR search efficiency, a decorrelation method applies an admissible integer unimodular matrix to eliminate the off-diagonal elements of the ambiguity variance matrix to reduce the correlation among the entries of ambiguity vector. This transformation involves iteration procedures. However, it is often the case that during the decorrelation process, effect of a bias in one measurement can be propagated and amplified onto many others, leading to more than one wrong integers. . In this paper, the reliability of PAR method is analysed. The impact of decorrelation process on how a bias may be amplified is investigated in detail. A partial decorrelation scheme is introduced to avoiding the amplification of an ambiguity bias. In addition, a new criterion of determining the number of fixing ambiguity based on the predefined success rate and dilution of precision is proposed for the PAR method to meet both the accuracy and reliability requirements. An example data set of multiple constellations, simulated by means of Virtual Galileo Constellation (VGC), is analysed to demonstrate the importance of reliability in the PAR method with multiGNSS constellations. KEYWORDS: Reliability, Partial ambiguity resolution, Multi-GNSS constellations, Decorrelation method
Cycle Slip Detection Algorithm by Integrating Vehicle and Inertial Sensors for Land Vehicle Users Junesol Song Mechanical and Aerospace Engineering, and the Institute of Advanced Aerospace Technology/Seoul National University/South Korea +82-2-880-7395(phone), +82-2-888-0559(fax), firstname.lastname@example.org Younsil Kim Mechanical and Aerospace Engineering/Seoul National University/South Korea +82-2-880-8918(phone), +82-2-876-6649(fax), email@example.com Byungwoon Park Cadastral Research Institute/Korea Cadastral Survey Corporation/South Korea +82-2-3774-2331(phone), +82-2-3774-2319(fax), firstname.lastname@example.org Changdon Kee Mechanical and Aerospace Engineering/Seoul National University/South Korea +82-2-880-1912(phone), +82-2-888-2069(fax), email@example.com Achieving cm-level positioning accuracy, carrier-phase based positioning methods, such as RTK, and Network RTK are widely used for services demanding high accuracy positioning; surveying, aircraft navigation, land vehicle and etc. Especially for land vehicle use, there is an on-going R&D project whose goal is to prevent car accidents involving vehicles carrying hazardous materials by monitoring their positions which are estimated by RTK, whether they deviate the designated lane or not. The project is supervised by Korea Aerospace Research Institute and many universities are participating including Seoul National University. The RTK and Network RTK provide accurate positioning results but they are very vulnerable to cycle slips. Cycle slip is a jump on integer ambiguity in carrier-phase measurement due to instantaneous loss of phase lock and it causes discontinuity in measurement. The accuracy of the positioning result from RTK or Network RTK can be easily degraded due to cycle slips. Therefore, carrier-phase measurements should be tested for cycle slip detection prior to calculate position. This paper proposes cycle slip detection algorithm especially for land vehicle application. This algorithm integrates odometer and gyro sensors. Odometer is a device that measures mileage and speed of vehicle based on rotations of the wheel, thus it gives output values continuously and also reliably and gyro sensor is used for estimating heading of the vehicle. They are used for estimating current user position based on previous position of user. Since it is obvious that there is a trade-off relation between sensor specification and cycle slip detection performance, we formulated error equation of the proposed cycle slip detection algorithm and used simulation data to select odometer and gyro sensors with appropriate specifications for cycle slip detection. This paper includes simulation results of selecting appropriate sensor specification and performance evaluation of the proposed cycle slip detection algorithm. KEYWORDS: Cycle Slip Detection, Land Vehicle, Carrier-phase based positioning, Inertial Sensors
Multipath & Reflectometry
0900 - 1040
GPS Bistatic Radar for Target Detection and Estimation using Antenna Arrays Chow Yii Pui School of Electrical & Electronic Engineering, University of Adelaide Gate 5, Frome Rd, SA 5005 Tel: +61 8 8303 8314 Email: firstname.lastname@example.org Matthew Trinkle School of Electrical & Electronic Engineering, University of Adelaide The University of Adelaide Tel: +61 8 8303 4708 Email: email@example.com Using GPS signals in a passive bistatic radar system requires a very high sensitivity receiver system due to
the extremely weak GPS transmission signal power. High sensitivity receivers can be made using large scale, high gain antenna arrays and long integration periods. The availability of low cost integrated RF front ends at GPS frequencies allows large scale antenna arrays to be built relatively cheaply. A low cost receiver is developed and is intended to be used with a large scale antenna array in the future. At the current stage, an experiment that utilised a 7 elements dual-polarised patch antenna array to detect a nearby target has been performed. This array is intended to be a sub-array of a larger array to be built in the future. A nearby target such as a moving train will be used to test the basic functionality of the system and give a benchmark for estimating the number of antennas required for the receiver to be able to detect an object of similar size at larger distance, such as an aircraft. In this paper, the results from this experiment are analysed and will be presented. This experiment is generally based on the experience from the last experiment which is conducted using a dual-polarised horn antenna pointed at the railway tracks to detect an approaching train. New techniques for improving the performance of target detection using multiple-input and multiple-output (MIMO) concepts will also be discussed. KEYWORDS: Bistatic radar, Global Positioning System, Target detection, Antenna array, MIMO
A Gain/Phase and Mutual Coupling Calibration Algorithm for GPS Antenna Array in the Presence of Multipath Zili XU School of Electrical and Electronic Engineering The University of Adelaide, Adelaide, SA 5005, Australia Phone: +61 8 8303 8314, Email: firstname.lastname@example.org Matthew Trinkle School of Electrical and Electronic Engineering The University of Adelaide, Adelaide, SA 5005, Australia Phone: +61 8 8303 4708, Email: email@example.com Doug A. Gray School of Electrical and Electronic Engineering The University of Adelaide, Adelaide, SA 5005, Australia Phone: +61 8 8303 6425, Email: firstname.lastname@example.org Antenna array techniques have been widely applied to the GPS area. However, in order to practically implement these techniques, GPS antenna array calibration is required. In this paper, a GPS antenna array calibration algorithm which can estimate the array orientation error, gain/phase errors and mutual coupling effect in the presence of multipath using GPS signals as the disjoint calibrating sources is proposed. The algorithm also uses the Wiener filter to estimate the number of multipath signals before the iterative calibration process and thus improves the calibration accuracy. The proposed algorithm is verified by simulation. KEYWORDS: array calibration, multipath, disjoint sources
Assessment of Multipath Mitigation with Vector Tracking Loop Li-Ta Hsu National Cheng Kung University, Tainan 70101, Taiwan +886-6-2349294 / Qmohsu@gmail.com Shau-Shiun Jan National Cheng Kung University, Tainan 70101, Taiwan +886-6-2349294 / email@example.com Multipath is the major concern for the design of a GNSS receiver, and many prior researches are working on its mitigation algorithms. One of the promising designs to mitigate multipath problem is the use of the vector tracking loop, and thus this paper will investigate the possible multipath mitigation technique based on a vector tracking design with Extended Kalman Filter (EKF). The concept of vector tracking is to utilize an EKF to combine the tracking process and the navigation process into one single process. One of the benefits using the vector tracking process is that the conventional tracking and navigation processes are now done by one vector tracking process. Because all channel processes are combined in the vector tracking process, it therefore has higher processing gain that enables the receiver to operate under low signal power and high dynamic scenarios. The conventional design of the code loop discriminator is sensitive to the multipath effect and resulting attenuation in the carrier to noise ratio of the acquired satellite which may cause loss of code lock. With the high processing gain of the vector tracking loop, it is possible for a vector tracking loop to continue tracking the satellite while strong multipath effect is presented. In this paper, two multipath mitigation techniques based on the code discriminator design, namely narrow correlator and strobe correlator, will be applied to gain possible improvement in the multipath mitigation by the vector tracking loop.
Finally, the results of the performance comparison study for different correlator designs of the vector tracking loop are shown with the real GPS signal. KEYWORDS: Vector tracking loop, extended Kalman filter, multipath mitigation, correlator.
Analysis of the Multipath Effect on Carrier Smoothed Code Measurements Heon Ho Choi (1) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Young Hoon Han (2) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Sung Lyong Cho (3) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Moon-Beom Heo (4) Department of Electronics Engineering/Korea Aerospace Research Institute/Korea email@example.com Chansik Park (5) Department of Electronics Engineering/Chungbuk National University/Korea firstname.lastname@example.org Sang Jeong Lee (6) Department of Electronics Engineering/Chungnam National University/Korea email@example.com In applications where more accurate positioning is required, lots of research has been reported adopting CDGPS (Carrier phase Differential GPS) which is widely used in precise positioning and surveying. To use code and carrier measurements for high precision GNSS positioning in the epoch-by-epoch manner, the quality of code measurements is important because the accuracy of the float solution depends on the quality of code measurements and the success rate of the integer ambiguity resolution is affected by the accuracy of the float solution. Therefore, the probability of fixing correct integer estimation can be increased by improving the quality of code measurements. The accuracy of the code measurement can be improved by using the carrier smoothing method. Hence, the accuracy of the float solution using the carrier smoothed code measurements is expected to be enhanced. However, the multipath effect on the carrier smoothed code measurement has not been analyzed theoretically. This paper analyses the effect of the multipath on the carrier smoothed code measurement and the float solution theoretically, and evaluates the analysis result using a software-based simulator. KEYWORDS: CDGPS, Carrier smoothing method, Float solution, Multipath
Sea Surface Roughness Estimation Using Signals for Multiple GPS Satellites Kegen Yu School of Surveying and Spatial Information Systems, University of New South Wales, Australia Tel: +61 2 9385 4206, Fax: +61 2 9313 7493, Email: firstname.lastname@example.org Chris Rizos School of Surveying and Spatial Information Systems, University of New South Wales, Australia Tel: +61 2 9385 4205, Fax: +61 2 9313 7493, Email: email@example.com Andrew Dempster School of Surveying and Spatial Information Systems, University of New South Wales, Australia Tel: +61 2 9385 6890, Fax: +61 2 9313 7493, Email: firstname.lastname@example.org Global Navigation Satellite System reflectometry (GNSS-R) has recently drawn significant attention since it can be employed in a range of applications including sea state, ocean altimetry, soil moisture measurement, and disaster (e.g. flooding, bushfire, and earthquake) monitoring. Although research on GNSS-R in the past two decades has made advances, there are no (or few) real applications of the technique. This is mainly because GNSS-R is still not a mature technique, there are no satellite-borne missions, there are few systematic airborne experiments, and GNSS-R is not yet able to provide information with high enough resolution and reliability. The authors are investigating new approaches to improve the performance of the GNSS-based geophysical parameter estimation. This paper focuses on the sea surface roughness estimation through an analysis of the reflected signal power. In particular, the theoretical modelling of the sea wave and surface scattering is studied in detail. Solution-level and waveform-level combination techniques
are proposed to improve the estimation accuracy through jointly processing the measurements of the reflected signals which are transmitted by multiple GNSS satellites. These combination methods also can be employed for other parameter estimation tasks. Airborne experiments were carried out by a UNSW -owned light aircraft over the sea off the coast of Sydney. The data were logged using the NordNav software receiver which has four front-ends so that the signals arriving at the LHCP (left hand circularly polarized) and RHCP (right hand circularly polarized) antennas could be recorded simultaneously. Both the delay waveforms and delay-Doppler waveforms were generated from the processing of the real data. Theoretical delay waveforms were also generated. The preliminary results confirm that the waveform-matching estimation method is not suited for scenarios where the flight height is below 500 m. KEYWORDS: Sea surface roughness estimation, reflected GNSS signals, multiple GNSS satellites.
0900 - 1040
Interference Localisation within the GNSS Environmental Monitoring System (GEMS) Ediz Cetin University of New South Wales, Australia Tel: +61293854190 E-mail: email@example.com Ryan J. R. Thompson University of New South Wales, Australia Tel: +61293854184 E-mail: firstname.lastname@example.org Andrew G. Dempster University of New South Wales, Australia Tel: +61293856890 E-mail: email@example.com Due to their low-power levels, GPS signals are very susceptible to interference from either intentional or unintentional sources. This vulnerability is further aggravated by the increased reliance of the civilian infrastructure on GPS for time synchronization. This brings about the pressing need for detection and localisation of the interferers in real-time to prevent disturbance to everyday operation of this infrastructure. This paper details the upgrades to one such system, GNSS Environmental Monitoring System (GEMS) which consists of a number of sensor stations connected to a central processing unit, to achieve real-time interference localisation. The paper describes the GEMS environment and details and compares performance of various time and frequency domain Time Difference of Arrival (TDOA) estimation approaches. KEYWORDS: Interference, TDOA, Localisation.
Detection and Jammer-to-Noise Ratio Estimation of Interferers Using the Automatic Gain Control Ryan J. R. Thompson University of New South Wales, Australia. Tel: +61293854184 E-mail: firstname.lastname@example.org Ediz Cetin University of New South Wales, Australia. Tel: +61293854190 E-mail: email@example.com Andrew G. Dempster University of New South Wales, Australia. Tel: +61293856890 E-mail: firstname.lastname@example.org In this work two issues concerning the use of the Automatic-Gain-Control (AGC) gain level for detecting and estimating the Jammer-to-Noise (J/N) ratio of Radio-Frequency Interference (RFI) are investigated. In the presence of RFI the AGC will reduce the gain level to keep the rms noise level at the input to the Analogueto-Digital Converter (ADC) at a set level. As this level has to be estimated using quantized samples it was found that there is an error in the J/N estimate if the RFI is not a wideband signal. At J/N = 20dB, this estimation error is equal to 0.82dB for a Continuous-Wave (CW) RFI. By changing the specified histogram bin percentages this error can be minimised, allowing better J/N estimation with only a slight increase in the quantization loss when no interferer is present. Another issue that this paper analyses is the effect of temperature perturbations on the AGC gain level. To study the influence of this the AGC gain level along with the receiver temperature was monitored over a number of days utilising a receiver with a temperature sensor attached. The relationship between temperature and the AGC gain was found to be linear. Hence, by utilising this information and compensating for the AGC gain level changes due to temperature, interference
detection performance using the AGC could be improved by 10dB. This results in capability of detecting RFI down to a J/N of -8dB. KEYWORDS: AGC, Interference, Temperature, Detection, J/N.
Influence of GPS Satellites Cross-Correlation on the TDOA Measurements within the GNSS Environmental Monitoring System (GEMS) Ryan J. R. Thompson University of New South Wales, Australia. Tel: +61293854184 E-mail: email@example.com Ediz Cetin University of New South Wales, Australia. Tel: +61293854190 E-mail: firstname.lastname@example.org Andrew G. Dempster University of New South Wales, Australia. Tel: +61293856890 E-mail: email@example.com As the importance of GNSS to civilian infrastructure increases, the ability to detect and localise sources of interference that disrupts its operation becomes increasingly important. In order to calculate the time-delay measurements in a Time Difference Of Arrival (TDOA) based localisation system for localising interference to GPS within the GNSS Environmental Monitoring System (GEMS), data collected at different sensor stations need to be cross-correlated together. However, along with the interference signals, the collected sets of data contain the GPS signals themselves, which create undesired correlation peaks. These correlation peaks could be mistaken for weak interferers during the TDOA processing. This work investigates and reports on the behaviour of these correlation peaks and the impact they have on using TDOA techniques for localising interference. If the sensor stations are close together, the time-delays of the satellites will be close together. This causes a large cross-correlation peak near the zero delay point as the satellite signals arrive at the sensor stations at a similar time. As distance between the stations increases the cross-correlation peaks spread out, but there will be situations where the time-delays for individual satellites will overlap, again causing a larger central cross-correlation peak. This results in an increase of the interferer effective Signalto-Noise Ratio (SNR) required for its cross-correlation peak to be above the GPS cross-correlation peaks which affects the detection and estimation threshold. This work is part of an ARC Linkage grant with the University of New South Wales, University of Adelaide and GPSat Systems, which is looking into building a network of sensor stations that can quickly detect and geo-locate interference to GPS within a given area. KEYWORDS: TDOA, cross-correlation, interference.
Interference Angle of Arrival Estimation within the GNSS Environmental Monitoring System (GEMS) using Antenna Arrays Zili XU School of Electrical and Electronic Engineering The University of Adelaide, Adelaide, SA 5005, Australia Phone: +61 8 8303 8314, Email: firstname.lastname@example.org Matthew Trinkle School of Electrical and Electronic Engineering The University of Adelaide, Adelaide, SA 5005, Australia Phone: +61 8 8303 4708, Email: email@example.com This paper introduces the initial test results of an electronically steered antenna array for finding weak interference signals in the GPS band. This antenna array is part of a larger system that will use multiple antenna arrays to geo-locate interference signals based on Angle of Arrival and Time Difference of Arrival measurements. In this paper the antenna array hardware is introduced and some initial test results are presented for finding the DOA of the GPS satellite signals and an interference source. This work is part of an ARC Linkage grant with The University of New South Wales and GPSat systems which is looking into building a network of sensor stations that can quickly geo-locate interferences to GPS within a given area. KEYWORDS:DOA, interference, array orientation
0900 - 1040
Development of A Tsunami Monitoring System using GPS Buoy Yukihiro Terada (1) Kochi National College of Technology, Japan Phone: +81-88-864-5586, Email: firstname.lastname@example.org Teruyuki Kato (2) Earthquake Research Institute, the University of Tokyo, Japan Phone: +81-3-5841-5730, Email: email@example.com Toshihiko Nagai (3) Port and Airport Research Institute, Japan Phone: +81-46-844-5010, Fax: +81-46-841-8307, Email: firstname.lastname@example.org Shunichi Koshimura (4) Graduate School of Engineering, Tohoku University, Japan Phone: +81-22-795-7516, email@example.com Toshihide Miyake (5) Technical Research Institute, Hitachi Zosen Corporation, Japan Phone: +81-6-6551-9312, Email: firstname.lastname@example.org Hitoyoshi Nishimura (6) Machinery & Infrastructure H.Q., Hitachi Zosen Corporation, Japan Phone: +81-3-6404-0813, Email: email@example.com Satoshi Kunihiro (7) Kochi National College of Technology, Japan Phone: +81-88-864-5586, Email: firstname.lastname@example.org A new tsunami observation system has been developed, which employs an RTK-GPS technique to detect and monitor a tsunami in real-time manner before it reaches the coast. The GPS antenna attached on the top of a buoy floating at the sea surface is one of the important apparatus in this system. The estimated positions of the antenna includes not only tsunami but also all kinds of sea surface changes including wind waves, tides etc. The low pass is used for extracting tsunami. After a series of preliminary experimental studies, the operation-oriented experiments were conducted at two offshore sites. These systems succeeded to detect three tsunamis whose amplitudes are nearly 10cm. They are 23rd June 2001 Peru earthquake, 26th September 2003 Tokachi earthquake and 5th September 2004 Kii earthquake. These results showed that the GPS buoy is useful for early detection of tsunami. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has established the GPS buoy system for monitoring sea waves with twelve GPS buoys along the Pacific coast of Japan since the year of 2007. The experimental GPS buoy that was established off Cape Muroto, Southwest Japan, is continuously operating until now. These systems also succeeded to detect 28th February 2010 Chile earthquake and 11th March 2011 Tohoku-Off earthquake tsunamis. Currently, the GPS buoy system uses a RTK-GPS which requires a land base for precise positioning of the buoy. This limits the distance of the buoy from the coast to, at most, 20km. There are two problems to be solved to deploy the buoy for farther distance from the coast: one is that positioning accuracy decreases as the distance increases and the data transmission by radio becomes difficult for a long distance. The improved RTK method and 400MHz radio system for 50km long baseline in the Muroto GPS buoy are under examination. Moreover; introducing a new algorithm of precise point positioning with ambiguity resolution method is also planned for 100 km offshore observation. KEYWORDS: GPS, Tsunami, Precise positioning, Real-time monitoring
Study on Precise Positioning for Maritime Transportation Safety Deuk-Jae Cho Korea Ocean Research & Development Institute / KOREA Phone: +82-42-866-3683 / E-mail: email@example.com Sulki Park Korea Ocean Research & Development Institute / KOREA Phone: +82-42-866-3685 / E-mail: firstname.lastname@example.org Sang-Hyun Park Korea Ocean Research & Development Institute / KOREA Phone: +82-42-866-3681 / E-mail: email@example.com
Currently geographical position of the seafloor and the depth of water, height of bridges and facilities, and height of the keel and the mainmast of vessels are established by tidal datum. But it is dependent on time and doesn‟t have a good accuracy. Many vessels determine overhead clearance by a rule of thumb based on their draft for maritime navigation. As a result, when vessels navigate, they don‟t have good overhead clearance. Especially, they don‟t calculate overhead clearance correctly and so it is occurred maritime accidents that the mainmast of vessels is bumped against overhead facilities. When actual accident is occurred, it causes not only copious restoration expenses but also environmental pollution due to oil spill, bridge damage, and electric power supply equipment damage. In order to avoid accidents, it is necessary to determine the overhead clearance of vessels in real-time using precise positioning technology while travelling through the canal and under the bridges for safe navigation. This paper proposes architecture to secure overhead clearance and observation equation for precise positioning. This observation equation is evaluated by analysing residual errors. And software platform for precise positioning is evaluated by using measurements acquired in the test-bed. KEYWORDS: maritime navigation, overhead clearance, maritime accident, precise positioning
Performance Analysis of Carrier Smoothed DGPS for Swarm Robots Hyun Ja Im (1) Robot/Cognitive System Research Department Intelligent Robot Control Research Team Electronics and Telecommunications Research Institute, Korea Tel: +82-42-860-3950, Fax: +82-42-860-1566, firstname.lastname@example.org Ji-won Park (2) Department of Information and Communication Engineering Chungnam National University, Korea Tel: +82-42-821-7607, Fax: +82-42-824-6807, email@example.com Jeong-Min Im (3) Department of Information and Communication Engineering Chungnam National University, Korea Tel: +82-42-821-7607, Fax: +82-42-824-6807, firstname.lastname@example.org Chang Eun Lee (4) Robot/Cognitive System Research Department Intelligent Robot Control Research Team Electronics and Telecommunications Research Institute, Korea Tel: +82-42-860-4823, Fax: +82-42-860-1566, email@example.com Young-Jo Cho (5) Robot/Cognitive System Research Department Intelligent Robot Control Research Team Electronics and Telecommunications Research Institute, Korea Tel: +82-42-860-1529, Fax: +82-42-860-1566, firstname.lastname@example.org Sung Hoon Kim (6) Robot/Cognitive System Research Department Intelligent Robot Control Research Team Electronics and Telecommunications Research Institute, Korea Tel: +82-42-860-6767, Fax: +82-42-860-1566, email@example.com Tae-Kyung Sung (7) Division of Electric and Computer Engineering Chungnam National University, Korea Tel: +82-42-821-5660, Fax: +82-42-824-6807, firstname.lastname@example.org Multiple swarm robots are more efficient than a single robot when the assigned task is complex and the workspace is large. Thus, many researches have been focused on designing a scheme for controlling the swarm robots without any collision or duplicated mission assignment. To meet with the task efficiency and successful control of swarm robots, positioning error less than tens of centimeters for each robot is desirable. The positioning accuracy of standalone GPS is about 10~15m. By using code DGPS, some error sources in standalone GPS are eliminated and the positioning accuracy is improved to 1~2 meters. When the carrierphase measurements are used to smooth code measurements, the accuracy is improved to 0.7~1.5m. In the CSDGPS (Carrier Smoothed Differential GPS), real-valued integer ambiguities are estimated by using code and carrier-phase measurements. This paper presents performance analysis of CSDGPS for swarm robots. Considering the accuracy, it seems that CSDGPS method alone is not appropriate for swarm robots. Because most of the CSDGPS error is a bias induced by integer ambiguity error, the shape of trajectory that is generated according to robot motion is very accurate with accuracy less than few centimeters. When the CSDGPS is used together with trajectory compensation method such as SLAM (Simultaneous Localization And Mapping), positioning accuracy can be less than few centimetres. Moreover, multiple swarm robots are used to generate distributive partial maps and they are integrated together to perform CSLAM (Cooperative SLAM). In this case, CSDGPS is very helpful to reduce computation of CSLAM. This paper analyse the performance of the CSDGPS with low cost
GPS receiver. The experimental results show that CDGPS provides satisfactory trajectory accuracy for SLAM in intelligent swarm robots. KEYWORDS: CSDGPS, Swarm robot, Position trajectory
The Principle of Determining the Geopotential Difference Between Two Points on Ground Using GNSS Signals WenBin Shen Department of Geophysics/Key Lab. of Geospace Environment and Geodesy, School of Geodesy and Geomatics, Wuhan University, Wuhan, China Tel.:+86 27 68778857-815; Fax: +86 27 68778825; e-mail: email@example.com The geopotential (gravity potential) plays a key role in physical geodesy and has broad applications in various fields and branches. According to general relativity theory, during the propagation of a light signal (electromagnetic wave) between two arbitrary different equi-geopotential surfaces, there exists a gravity frequency shift of this signal. This is the well-known gravity frequency shift effect, referred to as frequency shift principle, confirmed by various physical experiments. Based on this principle, one may determine the geopotential difference as well as the orthometric height difference between two separated points P and Q (even they are located in two separated continents by oceans) using the simultaneously-received signals which are sent out by a Global Navigation Satellite System (GNSS). One of advantages conveyed in this new approach lies in that it may unify the world (orthometric) height datum system. This paper reviews the principle of determining the geopotential using GNSS signals, provides new progress related to this subject and prospects the potential of this new approach for determining the geopotential and its related applications. KEYWORDS: General relativity principle; gravity frequency shift; GNSS signal; geopotential determination.
A Comparative Analysis of Displacement Detection Methods Using Locata Mazher Choudhury School of Surveying and Spatial Information Systems, University of New South Wales, Australia firstname.lastname@example.org Bruce Harvey School of Surveying and Spatial Information Systems, University of New South Wales, Australia email@example.com Chris Rizos School of Surveying and Spatial Information Systems, University of New South Wales, Australia firstname.lastname@example.org Alarm algorithms for displacement detection methods are one of the key components of an automatic displacement monitoring system used for monitoring any large structure (such as dams, bridges etc.). Methods such as Shewhart algorithm, moving average algorithm weighted moving average algorithm (WMA), exponentially weighted moving average algorithm (EWMA), cumulative sum algorithm (CUSUM) are used extensively to detect displacement, or in other words shifts in the mean and/or process variance. These methods and conventional least squares adjustment analysis are used extensively in GNSS displacement monitoring applications. Locata Corporation‟s positioning technology “Locata” provides centimetre-level accurate position solution with millimetre-level precision. This technology can complement (or augment) or even replace GNSS in environments with bad satellite geometric distribution or poor received satellite signal levels. In this paper the Shewhart and CUSUM algorithms are implemented and compared with conventional least squares adjustment. Two experiments were conducted at the University of New South Wales to analyse Locata‟s performance. Simulated movement was introduced for algorithm testing. After generating the coordinate solution, the three displacement monitoring algorithms were tested. In addition the prerequisite requirements of these methods were also analysed. Prerequisite includes checking autocorrelation and checking residuals for zero mean normal distribution. An autoregressive model was used to model autocorrelation. Results show that CUSUM and conventional displacement test performs better than the Shewhart algorithm. KEYWORDS: Locata, Displacement monitoring application
PPP & Carrier Phase
1110 - 1250
Precise Point Positioning - Where are we now? Thomas Grinter Survey Infrastructure and Geodesy, Land and Property Information NSW Department of Finance & Services, Bathurst NSW 2795, Australia Tel: +61-2-6332 8211, Fax: +61-2-6332 8479, Email: Thomas.Grinter@lpi.nsw.gov.au Craig Roberts School of Surveying and Spatial Information Systems, University of New South Wales Sydney NSW 2052, Australia Tel: +61-2-9385 4464, Fax: +61-2-93137493, Email: email@example.com The concept of Precise Point Positioning (PPP) using Global Navigation Satellite System (GNSS) technology was first introduced in 1976. However, it took until the 1990s for PPP to generate interest amongst the greater GNSS community. Over the last two decades, dual-frequency PPP has been extensively researched, and several PPP online services and software packages have been developed. This research has shown that centimetre-level point positioning is not only achievable in post-processed static mode, but potentially also for real-time applications, with a single GNSS receiver. With the advent of cost-effective, accurate, Real-Time Kinematic (RTK) positioning provided by an increasing number of Continuously Operating Reference Station (CORS) networks around the world, the focus of PPP has shifted to real-time or near real-time solutions. Real-time and near real-time correction products from organisations such as the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL), the International GNSS Service (IGS) and Natural Resources Canada (NRCan) allow PPP to potentially offer a viable alternative to RTK solutions in some circumstances, while maintaining the advantages of PPP over differential real-time products. However, several limitations still remain, primarily the long convergence times needed to resolve ambiguities, currently restricting the use of PPP for real-time applications. This paper provides a brief history of the development of PPP and reviews the advances made in PPP in the last two decades with an emphasis on the potential to utilise PPP as a â€žfill-inâ€&#x; service for existing CORS networks in areas where dense CORS coverage is not justified, e.g. due to low population density. This paper also outlines the current limitations and possible future direction of PPP. KEYWORDS: Precise Point Positioning, GNSS, CORS, precise orbits, precise clock corrections.
An Accurate Single Point Positioning Method with Prediction Mode for LEO Satellites Yuanyuan Jiao (1) 1. Dept. of Mathematics and Systems Science, National University of Defense Technology, China 2. School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: 61-4-05279093, Fax: 61-2-93137493, firstname.lastname@example.org Yong Li (2) School of Surveying & Spatial Information Systems, The University of New South Wales, Australia Tel: 61-2-93854173, Fax: 61-2-93137493, email@example.com Jiongqi Wang (3) Dept. of Mathematics and Systems Science, National University of Defense Technology, China Tel: 86-13787198870, Fax: 86-731-84574234, firstname.lastname@example.org Haiyin Zhou (4) Dept. of Mathematics and Systems Science, National University of Defense Technology, China Tel: 86-13973165101, Fax: 86-731-84574234, email@example.com Chris Rizos (5) School of Surveying & Spatial Information Systems,The University of New South Wales, Australia Tel: 61-2-93854205, Fax: 61-2-93137493, firstname.lastname@example.org For many applications the single-frequency stand-alone GPS receiver operating in single point positioning mode is still the preferred choice because of its relative simplicity, low cost and robustness. This is especially the case for spaceborne applications. However it is well known that single epoch positioning accuracy in stand-alone mode is not very high due to a number of factors, including GPS ephemeris error, satellite clock residual error, ionospheric delay, multipath, and tropospheric refraction. In this paper the authors propose an Extended Kalman Filter (EKF) for increased accuracy single epoch absolute positioning of Low Earth Orbit
(LEO) satellites, which includes a prediction capability that uses a satellite orbital dynamics model. The combination of pseudorange and carrier phase is used as observations which can reduce the influence of ionospheric delay. Systematic errors, such as GPS ephemeris or satellite clock residual errors, and ambiguities are taken into account as a single error term for each visible GPS satellite. However they are different for the different GPS satellite measurements. Thus, to estimate them together with position parameters the state vector would become large and traditional methods cannot be used. Nevertheless, by adding the prediction information, all variables can be estimated and the influence of the errors is effectively constrained, though at a cost in increased computing time. Promising experimental results demonstrate the validity and effectiveness of the proposed method. In the scenario that ionospheric delay is relatively small, and the proposed method results in single point positioning accuracy improvement of at least 25%. If the scenario involved larger ionospheric delay, the positioning accuracy would be expected to be improved about 90%. KEYWORDS: single point positioning, prediction, Extended Kalman Filter
Outlier Detection Performance in Precise Point Positioning Changhui Xu School of Surveying and Spatial Information Systems, University of New South Wales, Australia School of Environment and Spatial Information, China University of Mining and Technology, China 0425426468, email@example.com Jinling Wang School of Surveying and Spatial Information Systems, University of New South Wales, Australia Jinxiang Gao School of Environment and Spatial Information, China University of Mining and Technology, China With the development of iono-free solution, provision of IGS orbit and clock products, high precision GNSS positioning with a single receiver, usually named Precise Point Positioning (PPP), has been playing an increasingly important role in many applications. PPP is to obtain the highly precise coordinates of the receivers, so it is necessary to establish the mathematical model according to the mechanism of the motion of the platform and geometric relationship for the measurements used. The commonly used method to describe these motion and relationship is the Gauss-Markov models which are then used in the Kalman filter, to produce optimal estimation of the parameters, only when the model is realistic. However, it is well known that GPS/GNSS measurements may be contaminated with outliers, which will certainly have an impact on the reliability of the results, and even the convergence period. If these outliers are not correctly identified, the results may be biased and the precision will be decreased. Therefore, it is necessary to analyse the outlier detection performance first. The experiment demonstrates that the internal reliability gives the minimal detectable bias of 4cm in carrier phases and 3.5m in pseudo-ranges under the given priori variance and the effects of undetectable bias on the states is at the millimetre level after convergence. KEYWORDS: Precise Point Positioning, Outlier Detection, Reliability
Carrier Phase Based Positioning Algorithms Applied by Gaussian Sum Filters Yukihiro Kubo Department of Electrical and Electronic Engineering / Ritsumeikan University / Japan Phone: +81-77-561-5972, Fax: +81-77-561-2663, E-mail: firstname.lastname@example.org Yuu Matsunaga Department of Electrical and Electronic Engineering / Ritsumeikan University / Japan Phone: +81-77-561-5972, Fax: +81-77-561-2663, E-mail: email@example.com Koji Ohta Department of Electrical and Electronic Engineering / Ritsumeikan University / Japan Phone: +81-77-561-5972, Fax: +81-77-561-2663, E-mail: firstname.lastname@example.org Yoshihiro Ikebuchi Department of Electrical and Electronic Engineering / Ritsumeikan University / Japan Phone: +81-77-561-5972, Fax: +81-77-561-2663, E-mail: email@example.com Sueo Sugimoto Department of Electrical and Electronic Engineering / Ritsumeikan University / Japan Phone: +81-77-561-2673, Fax: +81-77-561-2663, E-mail: firstname.lastname@example.org In this paper, the measurement noise distributions of the GNSS observables are analyzed for the carrier phase based positioning methods such as short and long baseline relative positioning and PPP(Precise Point Positioning). And it is shown that the measurement noises in such positioning methods can be modeled by the weighted sum of Gaussian distributions better than ordinary single Gaussian distribution.
Then the positioning algorithms applied by the Gaussian sum filtering methods are shown. The filter applied in this paper is derived for a discrete time system with Gaussian sum distributed measurement noise, therefore the proposed algorithms can be implemented based on more accurate model of the observables. One of the problems for implementing the derived filter is that the number of Gaussian distributions can grow exponentially with time. The method to reduce the number of components is also discussed. The proposed algorithms are applied to the real receiver data, and the accuracy of positioning and variance and covariance information are compared with those of the Kalman filter. KEYWORDS: Gaussian sum filter, Kalman filter, carrier phase, measurement noise
A Study on Cycle Slip Detection and Correction in Case of Ionospheric Scintillation Wu Chen The Hong Kong Polytechnic University/Hong Kong, China email@example.com Shengyue Ji The Hong Kong Polytechnic University/Hong Kong, China Xiaoli Ding The Hong Kong Polytechnic University/Hong Kong, China This research is aiming at cycle slip detection and correction in case of ionospheric scintillation. Different from the normal situation without ionospheric scintillation, ionospheric delay cannot be neglected due to abrupt ionosphere change. In this case, ionosphere-free testing quantities for cycle slip detection and correction have to be used. In the past research, several geometry-free and ionosphere-free testing quantities have been proposed and, code measurements are commonly used in cycle slip detection and correction. Therefore, these geometryfree and ionosphere-free testing quantities are sensitive to code observation noise and multipath. During ionosphere scintillations, the code noise level increases significantly which makes it difficult for cycle slip correction. In this paper, detailed discussion on cycle slip detection and correction in case of ionospheric scintillation are given and a new method using non-geometry-free testing quantities in combination with geometry-free & ionosphere-free wide-lane testing quantity is described. Test data from Hong Kong is used to test the efficiency of the proposed method. Some limitations of the method to deal with long duration cycle slips are also discussed in the paper. Although the cycle slip detection and correction performance under strong scintillation is not as reliable as normal situations, this study will benefit for GPS data preprocessing during the next solar active cycle. KEYWORDS: GPS, ionosphere, scintillation, cycle slip, detection and correction.
Chinese Satnav Systems
1110 - 1250
Research on BEIDOU and Modernized GNSS Multi-constellation Integrated Navigation ZENG Qinghua Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-808, firstname.lastname@example.org, www.nuaanrc.com LIU Jianye Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-801, email@example.com, www.nuaanrc.com YANG Di Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-808, firstname.lastname@example.org, www.nuaanrc.com SUN Yongrong Navigation Research Centre, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China +86 25 84892304-803, email@example.com, www.nuaanrc.com
Satellite positioning system becomes the most widely used method of navigation for its advantage of allweather operation, high accuracy, passiveness, and broad signal coverage. On account of the high value in civil and military aspects, U.S, EU, Russia, P.R. China are committed to develop and update their global satellite positioning system (GNSS) positively. Because single satellite positioning system has less visible satellites, the positioning accuracy, reliability, security and availability of system can not be guaranteed when
signal is seriously interfered by terrible environment. Multi-constellation integrated system can overcome the shortcomings of each single navigation satellite constellation and improve the positioning performance greatly. Taking account of the update and modernization plan of each navigation satellite system, the positioning algorithm of multi-constellation integrated navigation system based on BEIDOU/GPS III/GLONASS/GALILEO was studied in the paper. Different coordinate systems and time systems of four satellite constellations were uniformed in the research programme; the least square method was used in the positioning calculation algorithm. Simulation results indicate: system based on BEIDOU & GPS III has the better performance than each single satellite navigation system, and the multi-constellation integrated satellite navigation system can greatly improve the positioning precision and reliability of GNSS receiver with more visible satellites. The result is helpful to modernized GNSS constellation, and has reference value for future GNSS application. The Navigation Research Centre (NRC, www.nuaanrc.com), Nanjing University of Aeronautics and Astronautics (NUAA), is engaged in the research of navigation and traffic technology. The researches focus on: GNSS theory and its application, Modern Inertial Navigation System, New Inertial Integrated Navigation Theory and Application, Mini Low Cost Navigation for Vehicles and GIS application and so on. Up to now a great deal of achievement has been made in the following fields, Strapdown Inertial Navigation System, Inertial Integrated Navigation System, Terrain Aided Navigation System, Fault-Tolerant Technique of Navigation System, and Modern Optimization Filtering Theory. In the recent years, Fiber Optical Gyros, Ring Laser Gyros and MEMS-based gyroscopes are especially investigated in NUAA NRC. The emphases mainly include the characteristic study on the modern inertia sensors, Error model and compensation and their applications in the inertial navigation systems. KEYWORDS: BEIDOU, GPS III, GNSS, Multi-constellation, integrated satellite navigation system
The Transmitting Satellite Navigation System Based on Communication Satellites Guoxiang Ai National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China Huli Shi National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China Lihua Ma National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China, firstname.lastname@example.org The transmitting satellite navigation system has been developed in China since 2003 as an alternative satellite system for navigation using C-band transponders onboard Geostationary Earth Orbit (GEO) communication satellites to transmit navigation message and ranging signals to users. Unlike the Global Navigation Satellite Systems (GNSS), such as the US Global Positioning System (GPS), Russian GLONASS, European Galileo and Chinese Compass satellite navigation system (Compass) and space based augmentation systems (SBAS), the system uses communication carriers at C-band and all the navigation and ranging signals are generated at a ground station instead of onboard satellites. Extensive positioning experiments within China have been performed since 2005. After the inclined-orbit operations are performed, some GEO satellites are moving in a very regular figure-8-like motion as seen from the ground, the inclination increases gradually with time and the satellites become Slightly Inclined Geosynchronous Orbit (SIGSO) satellites. These satellites can improve integrity of navigation system and positioning accuracy. Meanwhile, some transponders on these SIGSO satellites can provide a new satellite communication service. KEYWORDS: Transmitting satellite navigation system, Communication satellites, Navigation application, Inclined-orbit operations
Experimental Evaluation of Fast Beidou Orientation Ambiguity Resolution using the Lengthening Baseline Method Liangqing Lu College of Mechatronics & Automation, National University of Defence Technology/China Tel: 86-13874800505, Fax: 86-731-84576305-8212, Email: email@example.com School of Surveying & Spatial Information Systems, University of New South Wales/Australia Yong Li School of Surveying & Spatial Information Systems, University of New South Wales/Australia Tel: 61-2-9385-4173, Fax: 61-2-9313-7493, Email: firstname.lastname@example.org Chris Rizos School of Surveying & Spatial Information Systems, University of New South Wales/Australia Tel: 61-2-9385-4205, Fax: 61-2-9313-7493, Email: email@example.com
In order to use the 1st generation of Beidou GNSS for orientation determination, an ambiguity resolution method based on the principle of lengthening baseline is evaluated in this paper. The lengthening baseline method is implemented by placing the slave antenna at several specified locations which, together with the master antenna, form baselines of different lengths, with all baseline vectors pointing in the same direction. In the experiments a two-antenna Beidou receiver was used to record the carrier phase measurements. The experimental results have demonstrated the feasibility of determining the ambiguities of single-differenced carrier phase measurements by the lengthening baseline method. In the case of no cycle slips a 100% success rate has been achieved. The paper also investigates several deterministic factors that could affect the algorithmâ€&#x;s accuracy, such as baseline length, observation time span, and baseline direction. Being significantly different from the GPS-based orientation determination, the baselines should be aligned to the south-north direction as much as possible in order to maximise the Beidou orientation accuracy. The outcome of this work is applicable to orientation determination in actual Beidou applications. KEYWORDS: Beidou system, orientation determination, carrier phase measurements, ambiguity resolution.
Interference 2 / Antennas
1110 - 1250
Bit Error Rate Performance of SFH-Modulation Scheme System under Jamming Kwang-Chun Go Department of Electronics Engineering, Ajou University, Korea +82-31-219-2474, firstname.lastname@example.org Woo-Chul Park Defense Acquisition Program Administration, Korea +82-10-3718-3803, wcpark111@korea,com Ki-Keun Kim Agency for Defense Development, Korea +82-42-821-4833, email@example.com Jae-Hyun Kim Department of Electronics Engineering, Ajou University, Korea +82-31-219-2477, firstname.lastname@example.org The frequency hopping spread spectrum (FH-SS), in which a transmitter changes its carrier frequency according to a certain hopping pattern, is widely used in military network systems since it is highly resistant to deliberate jamming. In this paper, we consider PBNJ(Partial-Band Noise Jamming) and WPBJ(Worst case Partial-Band Noise Jamming) as jamming models, and we evaluate the bit error rate (BER) performances of SFH/NC-MFSK(NonCoherent M-ary Frequency-Shift Keying), SFH/SDPSK(Symmetric Differential PhaseShift Keying), and SFH/GMSK(Gaussian filtered Minimum-Shift Keying) modulation schemes under jamming conditions. We also analyze the performance of BER when the error correction of convolutional code is applied. We then suggest the best transmission method for each condition based on the results. We also proposed the characteristic of each modulation method that enables the change of low-speed voice and data communication that are very limited to satellite communication environments into high-speed data transmission regardless of jamming and interference. Through those modulation methods, we aimed at drawing the optimum Waveform for the next generation satellite communication by performing a function analysis and trade-off study via modeling and simulation in order to design a modulation method while considering jamming conditions. KEYWORDS: frequency hopping, bit error rate, jamming, convolutional code
GAJT - The First "Off The Shelf" Single Unit GPS Anti-Jam Antenna Rod MacLeod NovAtel Inc/Australia Phone: +61 400 883 601 Email: email@example.com Neil Gerein NovAtel Inc/Canada Phone +1403-295-4500 Email:firstname.lastname@example.org GPS has also become a critical element in PNT applications for both military and many civilian industries. GPS signals, however, are inherently weak and subject to both accidental and deliberate interference. GPS jamming devices are easy to obtain and jamming is growing more common. Recent examples of jamming have given the military and civil organizations cause for concern.
A robust and cost-effective solution to protect military and civil services from GPS jamming has been developed. This paper discusses GPS jamming and introduces a new, high performance GPS anti-jam technology, developed in collaborative partnership by NovAtel Inc. and QinetiQ Ltd. GAJT™ (pronounced “gadget”) is a single-unit, GPS interference mitigation system. GAJT is an antenna that nullifies jamming signals and allows GPS receivers to acquire and track satellite signals needed to ensure accurate position. Designed as a compact standalone system, GAJT provides anti-jam performance comparable to larger, multi-component Controlled Reception Pattern Antenna (CRPA) systems currently used by military organizations but at a significantly lower cost. The rugged, exterior-mounted unit easily integrates into new platforms and is compatible with existing GPS receivers. Manufactured using commercial, military-grade technology from Canada and the UK, GAJT provides an off-the-shelf solution for military and civil applications. KEYWORDS: Interference; anti-jam; antenna
A Lock Detector for Signal Blockage Detection in GPS Receivers Mi Hyun Jin (1) Department of Electronics Engineering/Chungnam National University/Korea email@example.com Heon Ho Choi (2) Department of Electronics Engineering/Chungnam National University/Korea firstname.lastname@example.org Deok Won Lim (3) Satellite Navigation Department/Korea Aerospace Research Institute/Korea email@example.com Chansik Park (4) Department of Electronics Engineering/Chungbuk National University/Korea firstname.lastname@example.org Sang Jeong Lee (5) Department of Electronics Engineering/Chungnam National University/Korea email@example.com The performance of GPS receivers can be degraded by the signal blockage. If the GPS signal is blocked, the C/N0 estimates and carrier phase measurements are affected in GPS receivers. Therefore, the signal blockage detection measure is required for reliable operation of GPS receivers. The carrier lock indicator is used in GPS receiver to detect the signal tracking status. However, it is hard to detect the signal blockage promptly since it uses moving average with a small forgetting factor in order not to be sensitive to noises. On the other hand, the lock indicator becomes sensitive to noise by increasing the forgetting factor while it provides quick response to signal blockage. This paper proposes a dual lock detector to achieve both the quick the signal blockage detection and stable signal tracking. The proposed dual lock indicator adopts different forgetting factors so that the GPS receivers can efficiently track the unstable signal and detect the signal blockage promptly. The performance of the proposed method is verified by simulation study. KEYWORDS: GPS, Signal blockage, Lock detector, Lock indicator, Forgetting factor
Improving GNSS Antennas Using Electromagnetic Band Gap Structures K J Parkinson (1) E P Glennon (2) A G Dempster (3) C Rizos (4) School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, 2052, Australia Email for corresponding author: firstname.lastname@example.org Electromagnetic Band Gap (EBG) structures have been proposed in numerous designs in recent years. Several structures have been used for a number of different frequencies and applications leading to significant size reductions with no loss of performance. A traditional approach to shielding a GNSS antenna from unwanted Multipath signals is to use a choke ring which is large, heavy and costly. The EBG antenna structure has been used successfully to eliminate the need for choke rings while gaining improvements in axial ratio (AR) performance. Fractal based designs using the Cartesian arrangement of EBG cells have
been used to miniaturise GNSS antennas. More recently radial EBG cell layouts have shown promising results while offering design flexibility and a further reduction in size. This paper investigates radial EBG antenna cell designs and presents performance improvements for GNSS applications in the areas of gain and multi-band operations. KEYWORDS: Radial antenna, EBG, GNSS, Axial ratio
Performance Evaluation of Array Antenna Processing with PM Algorithm for GNSS Receivers Yun Sub, Choi (1) Department of Electronic Engineering/Chungnam National University/Korea email@example.com Jae Young, Ko (2) Department of Electronic Engineering/Chungnam National University/Korea firstname.lastname@example.org Sang Wook, Hwang (3) Department of Electronic Engineering/Chungnam National University/Korea email@example.com Chansik Park (4) Department of Electronic Engineering/Chungbuk National University/Korea firstname.lastname@example.org Sang Jeong, Lee (5) Department of Electronic Engineering/Chungnam National University/Korea email@example.com The GNSS signal is vulnerable to intentional or unintentional interference due to low signal power. The GNSS receivers are easily affected by these interference resulting in the signal and giving erroneous PVT(Position, Velocity and Time). Therefore, the appropriate AJ(Anti-Jamming) technique is strongly required in military and SoL(Safety of Life) applications. Among many AJ techniques, array antenna based AJ technique are known to have outstanding performance. In the array antenna based AJ system, the output of each array antenna element is weightsummed to make the beams formed to GNSS signals or make the nulls to jamming signal. In this paper, we implement and evaluate the array antenna-based AJ system with PM(Power Minimization) algorithm to generate weighting matrix. The FPGA and DSP are used to implement the AJ system. For the real-time implementation of the PM algorithm, we adopt the fixed-point arithmetic and the adaptive weights computation method for the numerical resolution and efficient resource utilization. The characteristics of the logical operators are used to reduce the computational cost. The performance of the designed algorithm is evaluated by comparing with the performance of the PM algorithm based on the floating point arithmetic. KEYWORDS: Anti-jamming, Spatial PM, Fixed-point arithmetic
UAV’s Sponsored by Position Partner
1110 – 1250
Multi-Sensor Data Fusion for Small Unmanned Aircraft Systems Claus-Sebastian Wilkens Technische Universität Braunschweig, Institute of Aerospace Systems, Germany Phone: +49-531-3919968, Fax: +49-531-3919966, email: firstname.lastname@example.org
Peter Vörsmann Technische Universität Braunschweig, Institute of Aerospace Systems, Germany Phone: +49-531-3919960, Fax: +49-531-3919966, email: email@example.com The Institute of Aerospace Systems (ILR) at the TU Braunschweig, Germany develops and operates automated unmanned aircraft systems (UAS). Reliable and precise navigation data is essential for flight control of such unmanned systems. For this purpose, a low cost inertial measurement unit (IMU), which is based on micro-electro-mechanical systems (MEMS), was tightly coupled with a low cost receiver for the Global Positioning System (GPS). Besides the mentioned navigation data, air data information regarding barometric altitude and airspeed is beneficial for the control of automated aircraft. Thereto the institute's UAS are equipped with sensors for static and dynamic pressure.
MEMS based sensors suffer from highly drifting errors. Thus it is common practice to support the generation of the navigation solution by measurements of the GPS. This gain in accuracy is contrasted by the high dependency on the GPS signal. The aim of the presented research is to reduce this dependency by the use of other information available on board the aircraft such as air data. For the task of sensor data fusion an unscented Kalman filter (UKF) is designed to estimate the states needed for the determination of position, velocity, attitude, and air speed. Earlier research demonstrated the applicability of air data in the bridging of GPS outages. The bridging time is highly dependent on the accurate determination of the wind vector which implies the exact measurement of the air speed. With the mentioned approach of sensor data fusion more accurate air data information is available which in turn should lead to an increase in bridging time. In order to evaluate the presented UKF and its performance, inflight measurements from the meteorological mini UAS MÂ˛AV and its post processing software are used as a reference. KEYWORDS: unscented Kalman filter, GPS, INS, air data
Development of an Unmanned Aerial Vehicle Platform for Testing Positioning Technology Jiawei Xie University of New South Wales/Australia Tel: 0403547720 Fax: 61-2-9313-7493, Email: firstname.lastname@example.org Yong Li University of New South Wales/Australia Tel: 61-2-9385-4173, Fax: 61-2-9313-7493 email: email@example.com Zhi Chen University of Electronic Science and Technology/ China Tel: 86-13901010234, email: firstname.lastname@example.org The Unmanned Aerial Vehicle (UAV) technology is useful for various tasks ranging from aerial surveillance, homeland security and positioning operations. The capability for the unmanned aerial vehicles to operate completely autonomously in real environments is a great challenge. With a full featured UAV system, an aircraft could be competent for these tasks. Advances in computing, sensors, and communications technology make it possible to achieve autonomous performance and coordination of these vehicles in uncertain environment. This paper aims to design a UAV control system, which is mounted on a mini UAV helicopter. The system can be employed to test various sensors performance, communication protocols and their use on UAV controls. In the development, a mini RC helicopter is used for testing purposes. At the heart of the firmware of the system is the direction cosine matrix (DCM) computation which is used in control and navigation. Ground control station software receives the UAV system telemetry data from the XBee 900MHz RF module and displays the location on the Google map with the instant altitude and all sensor data. A new UAV control board is under development to further investigate the benefit of using different sensors, GPS modules and control algorithms. A Linux-based real-time kernel will be running on the new board to handle critical mission tasks. Development of application software for different research purposes will become easy and portable. KEYWORDS: Unmanned aerial vehicle, GPS, Inertial sensors, control system, Linux operating system.
Use of GPS/INS Observations for Efficient Matching of UAV Images Juan Shi School of Geodesy and Geomatics, Wuhan University, Wuhan, China School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Key Laboratory of Precise Engineering and Industry Surveying, State Bureau of Surveying and Mapping, Wuhan, China Tel: +610406922406 / email: email@example.com Jinling Wang School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Tel: +61400463668 / email: firstname.lastname@example.org Yaming Xu School of Geodesy and Geomatics, Wuhan University, Wuhan, China School of Surveying and Spatial Information Systems, University of New South Wales, Sydney, Australia Key Laboratory of Precise Engineering and Industry Surveying, State Bureau of Surveying and Mapping, Wuhan, China Tel: +8613507196246 / email: email@example.com
The recent availability of very high resolution imagery from unmanned aerial vehicles (UAV) remote sensing platform integrated with GPS/INS has unfolded a wide range of opportunities for using Earth-observing data. Although UAV can provide images with high resolution in a portable and easy way, such images only cover small area of the entire field of interest and are often highly deformed due to the unstable attitude. Therefore, a fast and accurate mosaic method is required to put all the images together to create a good view of the entire field. There are some matching algorithms based on image only such as scale-invariant feature transform (SIFT) and Harris operators that have been widely investigated. However they are often time-consuming and have low accuracy especially for big angle images. In this paper, we combined all the available geo-referencing information (GPS, INS, images) to dramatically improve the efficiency of image matching process. The proposed method can be divided into three steps; firstly, the GPS information is used to construct the image matching network, which can narrow down the searching space by giving a rough corresponding overlap area. Secondly, the attitude information from INS (the three angle elements) was used to find a suitable resampling method and geometric transformation model to calibrate the images, which can greatly correct the deformation. Lastly, SURF (Speeded Up Robust Features) algorithm was utilized to extract features and match the images sequentially. The proposed approach is demonstrated via a test case based on very high-resolution sequence images taken by the UAV system. KEYWORDS: Inertial navigation system (INS), Global positioning system (GPS), Image matching , SURF, Unmanned aerial vehicles (UAV).
Robust CP Positioning
Reliability Analysis of Robust Estimation for Use GNSS Positioning Ling Yang (1) School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Phone: +61 2 9385 4185 Fax: +61 2 93137493 email: firstname.lastname@example.org Jinling Wang (2) School of Surveying and Spatial Information Systems University of New South Wales, Sydney, NSW 2052, Australia Phone: +61 2 9385 4203 Fax: +61 2 93137493 email: email@example.com In GNSS positioning, least-squares estimation method has been traditionally used, however, the leastsquares method is extremely sensitive to outliers and may break down when the data including leverage points. As a result, two typical categories of approaches to controlling the outlier influence in the final leastsquares results have been developed over the years: outlier tests and robust estimation. The outlier tests are based on the assumption of fixed number and location of outliers which limits their practical applications. Comparatively, robust estimation methods may fail because of the masking and swamping effects due to the weak geometry in the system. However, unlike the outlier tests, robust methods do not have proper reliability measures. To gain further insight into robust estimation and compare it with outlier detection test, A numerical example for GPS single point positioning is analysed, by which the influence of masking and swamping effects on the robust estimation are analysed. Besides, the internal and external reliability measures in outlier detection methods are introduced into iteratively reweighted procedure and their variety tendency during the reweighted steps are discussed. The results show that these reliability measures highly rely on the selection of down weight observations which is probably mis-identified due to the negative masking and swamping effects, and a robust initial value of unknowns used in the robust estimation can alleviate these harmful effects on the down weight option and hence improve the precision and reliability of resolution. KEYWORDS: robust estimation; outlier tests; least median of squares; reliability measures; masking and swamping effects
A-RAIM vs. R-RAIM: A Comparative Study Yiping Jiang (1) The University of New South Wales/Australia Yiping.firstname.lastname@example.org Jinling Wang (2) The University of New South Wales/Australia Jinling.email@example.com GNSS Receiver Autonomous Integrity Monitoring (RAIM) has been widely used in civil aviation with the purpose of keeping the users notified of the integrity risk of the navigation solutions. It is based on the scheme of consistency check among redundant observations and therefore independent of any augmentation systems. With the modernized GPS and GLONASS, as well as the new GNSS systems (Compass, GALILEO) well underway, the increase in the number of satellites and the multiple frequency signals are available. It is therefore reasonable to pursue the possibility of using RAIM in civil aviation for more stringent procedures, such as LPV-200 for vertical guidance on a global scale. This possibility is explored by US Federal Aviation Administration (FAA) under the panel of GNSS Evolutionary Architecture Study (GEAS), which has attracted attention of researchers thereafter. Two major architectures have been identified as feasible choices to meet the LPV-200 requirement: a) Advanced RAIM (A-RAIM), b) Relative RAIM (R-RAIM). With different advantages and disadvantages for the two architectures, it is realistic to have a comprehensive comparison. And then, reasonable choices can be made based on the requirements for specific applications. The comparison is conducted mainly at the algorithm level. In this paper, the Multiple Hypotheses Solution Separation (MHSS) method based on local tests with multiple alternative hypotheses is adopted. Based on the common threat model, A-RAIM and R-RAIM are compared with results of VPL. The comparison of VPL within a world-wide map and a time series is provided to illustrate the difference. This paper is concluded with analysis and suggestions based on the comparison. KEYWORDS: RAIM, R-RAIM, A-RAIM, GNSS, Civil Aviation
Effects of Different Reference Receiver Setups on IMT Performance Hui-Chieh Hsu Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: firstname.lastname@example.org Shuo-Ju Yeh Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: email@example.com Shau-Shiun Jan Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: firstname.lastname@example.org As we know, GPS stand-alone is not reliable on civil aviation because of the lack of real-time monitoring mechanism. In the other hand, A GPS-aided aviation might be a solution to increase airspace capacity and efficiency for the growth of civil aviation. A real-time monitoring mechanism such as the Integrity Monitor Test-bed (IMT), a Ground Based Augmentation System (GBAS) ground facility prototype, is a solution since the enhancement of GPS service, flexibility, and curved path approach support. For the development and implementation of the IMT, the purpose of this work is to evaluate its performance in two considerations: one is robust database of the integrity monitoring algorithm; the other one is different geometric distribution of reference stations. According to the integrity monitoring algorithm of IMT, each reference station generates the specific detection criteria based on its own test statistic. Furthermore, the test statistic is sensitive to the environment of reference station, and so are the detection criteria. Thus, the data fusion would be executed for a proper database to improve the performance of integrity monitoring algorithm. In addition, the geometric distribution of reference stations is an important issue of the IMT implementation. For specific airport, the terrain or the scale of runway constrains the setup of reference stations. Therefore, a survey of proper setup is necessary in order to obtain the optimal performance of the IMT. Accordingly, several geometries of reference stations would be investigated. In this paper, the implementation procedures of the IMT algorithms is introduced, and the experiment results of both considerations are shown as well, Finally, the evaluation of the IMT performance would be presented in Stanford chart. KEYWORDS: Positioning System, Integrity Monitor Test-bed, Ground Based Augmentation System.
Performance Improvement of RTK By Using Variable-Mask Strategy Hideki Yamada Electronic Navigation Research Institute, Japan Phone: +81-422-41-3194, Fax: +81-422-41-3199, Email: email@example.com Tomoji Takasu Tokyo University of Marine Science and Technology, Japan Phone: +81-3-5245-7365, Fax: +81-3-5245-7365, Email: firstname.lastname@example.org Nobuaki Kubo Tokyo University of Marine Science and Technology, Japan Phone: +81-3-5245-7376, Fax: +81-3-5245-7376, Email: email@example.com Takeyasu Sakai Electronic Navigation Research Institute, Japan Phone: +81-422-41-3194, Fax: +81-422-41-3199, Email: firstname.lastname@example.org Akio Yasuda Tokyo University of Marine Science and Technology, Japan Phone: +81-3-5245-7365, Fax: +81-3-5245-7365, Email: email@example.com Real Time Kinematic (RTK) is one of the most precise positioning techniques, which calculates centimeterclass user positions by resolving carrier-phase integer ambiguities. With Russian GLONASS signals in addition to GPS, the ambiguity resolution process can be greatly helped by redundant measurements. While, the additional satellites often disturb successful ambiguity resolution by large multipath errors in severer conditions like in urban canyons. In such condition, C/N0-mask and elevation-mask are useful in order to prevent the effect of multipath errors. These masks are usually configured as fixed values. However, the aspect of distribution of multipath errors with respect to C/N0 or elevation is not clear in such environment. Therefore, the fixed thresholds for the masks may reject not only observations with large multipath errors but also fine observations with small multipath. The variable-mask strategy is apparently suitable compared to the fixed-mask in such cases. The objective of this paper is to introduce and evaluate the optimized algorithm to determine the variable-mask for RTK, as well as to show the quantitative distribution of multipath errors in urban canyon. In the algorithm, the mask threshold is changed dynamically, based on quality check of estimated ambiguities. In order to verify the algorithm, we conducted some experiments. Observation data was collected for 24 hours at a static point in severe condition. We used double-difference residuals at a precise position in order to estimate multipath errors. According to the analysis results, the multipath error is within 1 meter for 74 % of measurements with C/N0 of 30 dB-Hz. The suggested algorithm increases the ratio of correct fixed solutions up to 38 %, compared to 32 % at fixed mask and 18 % at no mask with conventional GPS+GLONASS. The proposed variable-mask strategy works well to improve the performance of RTK especially in severe condition. KEYWORDS: GPS+GLONASS RTK, Multipath, C/N0 mask, Elevation mask.
INS Aided Integrated Ambiguity Resolution for Robust Precise Positioning under the Week signal Environment Sul Gee Park Marin Safety & Pollution Response Research Dept./Korea Ocean R&D Institute/South Korea +firstname.lastname@example.org Sang Hyun Park Marin Safety & Pollution Response Research Dept./Korea Ocean R&D Institute/South Korea +email@example.com Deuk Jae Cho Marin Safety & Pollution Response Research Dept./Korea Ocean R&D Institute/South Korea +firstname.lastname@example.org Jung Won Lee Ocean Exploration System Research Dept./Korea Ocean R&D Institute/South Korea +email@example.com Currently geographical position of the seafloor and the depth of water, height of bridges and facilities, and height of the keel and the mainmast of vessels are established by tidal datum. Many vessels determine overhead clearance by a rule of thumb based on their draft for maritime navigations. As a result, when vessels navigate, they donâ€&#x;t have good overhead clearance. In order to avoid accidents, it is necessary to determine the overhead clearance of vessels in real-time using precise positioning technology while traveling through the canal and under the bridges for safe navigation. However, when vessels navigate the coast or an inland waterway, there are many bridges and facilities. These bridges and facilities give cause for week
signal of satellite. When receiver use week signal, Carrier phase based precise positioning is impossible and is hard to search and maintain of integrated ambiguity. Because measurement noise increases due to week signal environment and satellite DOP is poor. Therefore, these environment systems need robust precise positioning under the week signal. This paper proposes INS aided integrated ambiguity resolution for robust precise positioning under the week signal environment. This system use Code and carrier phase measurement of L1 and L2 signal and UofC observation model for precise positioning and then remove all potential error sources in the system. All errors caused by space segment, propagation, environment, and receiver need to be mitigated. The mitigation can be carried out by modeling, estimation, or observation combination. Most of the PPP errors, except for troposphere and receiver clock, can to some extent be mitigated through modeling. Integrated ambiguity resolution method is LAMBDA. When satellite signal is week, integrated carrier phase is estimated using dynamic characteristic of vessels based INS information. Carrier phase measurement is recomposed using estimated continuous and stable ICP information. The validity of propose method is shown through simulation. Simulation is performed two case that satellite signal is week both in the south direction and north direction. As a result, propose method shows normal signal environment result. KEYWORDS: Week signal environment, Ambiguity resolution, INS, precise positioning, carrier phase measurement.
Occultation / Space Weather
Radio Occultation Study Using 3-D Numerical Ray Tracing R. Norman, C. Wang, B. Carter, Y. Li, S. Gordon, K. Zhang Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, RMIT University, Melbourne, Australia +61 3 9925 3762 firstname.lastname@example.org J. Le Marshall Centre for Australian Weather and Climate Research (CAWCR), Australian government Bureau of Meteorology Australia +61 3 9669 4420 JLM@bom.gov.au Ray tracing techniques are commonly used for calculating the path of an electromagnetic signal in a medium specified by a refractive index, dependent upon position. Ray tracing is becoming an important tool for the operation of GPS L-band frequency propagation and in particular GPS Radio Occultation (RO) where accurate and near real-time results are required. In this study we take into consideration the cold magnetised plasma referring to the refractive nature of electromagnetic propagation in the ionosphere and atmospheric refraction due to wet and dry molecules and the permanent dipole moment of the water vapour molecule. Three dimensional numerical ray tracing techniques are used to simulate GPS L-band signals received by Low Earth Orbital (LEO) satellites and to investigate the variability of the signalâ€&#x;s path and strength as a function of time and position due to the refractivity gradients in the ionosphere and atmosphere. The numerical ray tracing technique involves synthesizing ray paths and ray tubes and producing ray parameters such as group path, phase path, angle of arrival and signal strength. The L-band frequency paths from the GPS to LEO satellites are simulated with a focus on signal paths traversing regions of the atmosphere and ionosphere where refractive gradients are greatest. The birefringence effects due to the earthâ€&#x;s magnetic field on the signals are investigated. KEYWORDS: Ray tracing, ionosphere, atmosphere
Constellation Design and Antenna Array Processing for GNSS Radio Occultation Mission Jyh-Ching Juang Department of Electrical Engineering, National Cheng Kung University, Taiwan email@example.com Yu-Hsuan Chen Department of Electrical Engineering, National Cheng Kung University, Taiwan firstname.lastname@example.org Yung-Fu Tsai Department of Electrical Engineering, National Cheng Kung University, Taiwan email@example.com Chung-Huei Chu National Space Organization, Taiwan
firstname.lastname@example.org The well-known FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission is a joint Taiwan/US science mission for weather, climate, and space weather research. The six LEO satellites constellation equipped with GPS receiver for Radio Occultation (RO) experiment has successfully provided a significant amount of RO data for numerical weather predication, weather forecasting, and space weather monitoring. Owing to the success of the FORMOSAT-3 program, a follow-on FORMOSAT-7 mission is being planned by NSPO and NOAA to develop a capability of providing operational continuity of global GNSS RO observations. In the paper, the requirements on the FORMOSAT-7 mission will be briefly reviewed. The constellation design for global coverage with sufficient temporal and spatial resolution, and the operation features for enhanced regional resolution will be described. According to the antenna limits, a single antenna cannot track the satellite over a wide range of azimuths. Furthermore, the retrieval quality depends on the RO observations. Accounting for weak signal of occultation environment, antenna array and digital beamforming approach are adopted to enhance the signal power in this paper. The Minimum Variance Distortion Response (MVDR) algorithm is used to compute the weights iteratively. Then, combine the signal of antenna array and track the signal by either closed-loop or open-loop. An experiment is conducted by receiving a real GPS satellite in low elevation angle which simulates the weakness of the occultation signal. Finally, the assessment of antenna array processing will be shown in the last segment. KEYWORDS: Constellation Design, Radio Occultation, FORMOSAT-7, Beamforming
The Application of Radio Occultation for Climate and Weather Monitoring and Numerical Weather Prediction in Australian Region J. Le Marshall, Y. Xiao, P. Steinle, K. Puri, T. Le Centre for Australian Weather and Climate Research (CAWCR), Australian government Bureau of Meteorology Australia +61 3 9669 4420 JLM@bom.gov.au R. Norman, K. Zhang Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, RMIT University, Melbourne, Australia +61 3 9925 3762 email@example.com A. Rea, R. Seecamp Australian government Bureau of Meteorology Australia +61 3 9669 4420 JLM@bom.gov.au L. Curucurull NASA, NOAA and DoD Joint Center for Satellite Data Assimilation (JCSDA), USA The GPS/MET mission, the CHAMP (CHAllenging Minisatellite Payload) mission(Germany), the SAC-C mission (Argentina), the GRACE (Gravity Recovery And Climate Experiment) mission(2 spacecraft, US/Germany), the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission and the Meteorological Operational satellite (MetOp) mission provide a new observation type for climate determination and operational meteorology which has been shown to provide significant information on the state of the atmosphere and ionosphere and has allowed significant improvements in the determination of current and future atmospheric state. It has also enabled important activities such as examination of radiosonde performance and an examination of ionospheric composition. Here two separate months of COSMIC radio occultation observations have been assimilated into the global ACCESS (Australian Community Climate Earth Systems Simulator) system which is being employed at the Australian Bureau of Meteorology to provide real-time operational forecasts. In these studies four dimensional variational assimilation (4DVAR) has been used to assimilate the radio occultation data into the global ACCESS system (ACCESS-G), which has been used to provide forecasts to five days ahead. For the periods studied, the accuracy of these forecasts has been compared to forecasts generated without the use of the radio occultation data. The forecasts using radio occultation data have been found to be improved in the lower, middle and upper troposphere. In addition, because of the relatively unbiased nature of radio occultation observations, they have been used to study the characteristics of radiosonde data, particularly in the Australian region and they have also been used to probe ionospheric content. The results shown here indicate their use has the potential to improve operational analysis and forecasting in the Australian Region and also to make a very important and unique contribution to vital tasks such as climate monitoring and regional reanalysis. KEYWORDS: Meteorology, weather forecasting, radio occultation, atmosphere, Climate
Space Weather Effects on the GPS Scintillation Levels Received From Radio Occultations (1)
B. A. Carter , R. Norman , C. Wang , Y. Li , S. Gordon , G. Hooper and K. Zhang (1) SPACE Research Centre, RMIT University, Australia ph: +61 3 9925 0356, email: firstname.lastname@example.org (2) GPSat Systems Australia, Macleod, Victoria, Australia ph: +61 3 9455 0041, email: email@example.com
The relationship between the global characteristics of the ionospheric scintillation S4 index and the level of geomagnetic activity is investigated. The 4-year dataset spans the bottom of the declining phase of solar cycle 23 and is used to study the diurnal and seasonal variations of the space-based S4 measurements obtained from a large number of Global Navigation Satellite System (GNSS) Radio Occultation (RO) events. The statistical patterns observed are used as quiet-time baselines to investigate the effects of geomagnetic disturbances on the measured ionospheric scintillation levels at different locations. In addition, these characteristics are investigated for different longitude sectors. Ground-based Ionospheric Scintillation Monitors (ISMs) are also employed to determine the relationship, if any, between the S4 index measured on the ground and the S4 index derived from GNSS RO in the Asian sector. The feasibility of utilising the RO S4 index as a proxy for the level of amplitude scintillation measured on the ground is also explored and discussed in the context of space weather-related GNSS scintillation prediction. KEYWORDS: Ionosphere, Space Weather, GNSS Scintillation, Radio Occultation
Investigation of Atmospheric Parameters in the Australian Region Using GPS Radio Occultation Technology (1)
C.S. Wang , K. Zhang , R. Norman , S. Gordon , Y. Li , J. Le Marshall , (1) (1) B.A. Carter and S. Choy (1)SPACE Research Centre and School of Mathematical and Geospatial Sciences/RMIT University/Australia +61-3-99251046 firstname.lastname@example.org (2)Bureau of Meteorology/Australia email@example.com GPS radio occultation (RO) is a space-based technique for sounding the Earth‟s atmosphere. The GPS RO technique uses GPS receivers onboard Low Earth Orbit (LEO) satellites to measure the radio signals emitted from GPS satellites to retrieve atmospheric information such as temperature, pressure and water vapour. This technique has the potential to improve numerical weather prediction and climate monitoring. The aim of this study is to utilise COSMIC data over the Australian region (110°E to 160° E and 10°S to 50° S) to analyse the difference between the RO results produced by two different data processing packages. The Radio Occultation Processing Package (ROPP) and the COSMIC Data Analysis and Archive Center (CDAAC) software packages are compared using a period of three days GPS RO data (January 1 to 3, 2010). It is shown that the dry temperature profiles retrieved from both the ROPP and CDAAC software packages are strongly correlated at altitudes between 10km and 25km. The average difference in the pressure profiles determined using ROPP and CDAAC (V2009.2650) is 0.12 - 1.54 hPa at 5 - 35 km altitude. The dry temperature varies from 0° to 3.5°. By comparing the ROPP with the two versions of CDAAC (V2009.2650 and V2010.2640), the difference in the average dry temperature can approach 1.6° at 25 - 35 km altitude and 0.9° at 5 - 10 km altitude. However, no obvious difference is found in the refractivity and the pressure when using the different versions of CDAAC. For refractivity and pressure, similar results in the Australian region can be obtained using different RO processing techniques. However, large differences in the dry temperature exist at 25-35 km altitude if different versions of CDAAC are used. KEYWORDS: GPS, Radio Occultation, Dry temperature, Pressure
Mixed Stream / Late Papers
A Study on Long-Term Predicted Ephemeris for GPS Satellite Cen XIAO Graduate School of Marine Science and Technology， Tokyo University of Marine Science and Technology firstname.lastname@example.org Chunming FAN Tokyo University of Marine Science and Technology email@example.com Tomoji TAKASU Tokyo University of Marine Science and Technology firstname.lastname@example.org Kimihiko UENO Tokyo University of Marine Science and Technology email@example.com Akio YASUDA Tokyo University of Marine Science and Technology firstname.lastname@example.org To shorten the TTFF (time to first fix) of GPS receivers, the long-term ephemeris technique has been recently developed. The existing technique, however, usually requires a communication link to obtain ephemeris information from an external server. Due to the external requirements, not all receivers can utilize such technique. In this paper, we propose a method which use past navigation messages to obtain the initial satellite positions, propagate them and predict the future satellite positions considering appropriate perturbations effecting the satellite orbit. We consider four kinds of perturbation for the precise orbit dynamics, which are the gravitational, attraction due to the sun and the moon, solar-radiation pressure (SRP), and general relativity. We revise each perturbation through precise models and predict the satellite orbit by the following procedure. First, based on the past navigation data for the last three days, we can calculate the initial satellite position and velocity, SRP parameters, and ERP (earth rotation parameters) based on the least square fitting to the past satellite positions derived from the ephemeris. Then, we use the satellite orbit parameters obtained from the previous step as the initial value and predict the satellite orbit‟s current position. With the predicted orbit, the long-term ephemeris can be generated. We have examined several models and optimized parameters for such orbit prediction. To evaluate the proposed method, we conducted some experiments. We adopted JGM-3 model with degree/order 8 for the gravitational and GSPM.04b for the SRP model. At any given point, the forecasted satellite positions within the next 72 hours based on the previous three days‟ navigation data, show that the mean value of maximum margin of error is below 7 m for all satellite position errors projected in users‟ viewing direction. The result demonstrates that the proposed method is helpful in obtaining the estimated user position immediately with confidence in accuracy in the case of emergency situations such as accidents or disasters. KEYWORDS: GPS, TTFF, least squares method, Satellite Orbit Prediction, Error Factor
Correlation of Land Surface Temperature and Vegetation Density Classified from Satellite Images Nang Mya Mya Nwe Tokyo University of Marine Science and Technology /Japan +813-5463-4232, email@example.com Shoko HASHIDA Meisei University Tokyo/Japan +814-2591-5111, firstname.lastname@example.org Yoshikazu KOIKE Shibaura Institute of Technology, Tokyo, Japan +813-5859-8301, email@example.com Akio YASUDA Tokyo University of Marine Science and Technology/Japan +813-5245-7365, firstname.lastname@example.org Land surface temperature (LST) is important in studying global warming. The knowledge of surface temperature is also important to a range of issues and themes in earth sciences central to urban climatology, global environmental change, and human-environment interactions. This study is intended to estimate surface temperature changes over the Hino City, Tokyo as a test site using the data from Landsat TM and ETM+ satellite Images. The emissivity per pixel is retrieved directly from satellite data and has been estimated as narrow band emissivity at the satellite sensor channel in order to have the least error in the surface temperature estimation. The retrieved LST has been investigated with respect to both of AMeDAS (Automated Meteorological Data Acquisition System) data that is a high-resolution surface observation network developed by Japan Meteorological Agency (JMA) and classified data from the visible and NIR channels of Landsat TM and ETM+ images. An extensive comparison will be done with the temperature measured by GPS data logger. The processing result shows strong correlation is observed between surface temperature and Normalized Difference Vegetation Index (NDVI) over different classes of classification. From this research, it is observed that the region having high amount of vegetation showed low mean surface temperature and the spatial layout of the land use/ land cover in the area has a great impact on the development of urban heat islands. And the retrieved values are in good agreement with an error of around 2ËšC. Therefore, this research is considered helping urban planning that should be adopted to avert or alleviate the effect of urban heat islands. KEYWORDS: Surface Temperature, Surface Emissivity, Landsat TM/ETM+, GPS data logger, NDVI
Global Tropopause Derived from COSMIC for Climate Study Y. Li(1), R. Norman(1), S. Wu(1), B. A. Carter (1), K. Zhang(1), C. Wang(1) (1) SPACE Research Centre, RMIT University, Australia email: email@example.com In this paper, tropopause height and tropopause temperature parameters derived from COSMIC radio occultation and radiosonde measurements based on two different tropopause definitions using four years data from 2007 to 2010 in global scale are performed and the results are analysed. The validation of RO temperature profiles against those from radiosonde data indicate the suitability of the RO data for tropopause study. Spatial variations of the tropopause parameters are investigated and the results show that most of the tropopause parameters are highly correlated with latitude and not much correlated with longitude. The suitability of lapse rate temperature (LRT) and cold point (CPT) definitions are investigated by analysing the agreement of the tropopasue parameters derived from both COSMIC and radiosonde data. Results indicate that the CPT definition is more suitable for low and middle latitude regions and the LRT definition is suitable for high latitude regions. KEYWORDS: GPS Radio Occultation, Tropopause, Lapse rate temperature, Cold point temperature.
The Airborne Science Initiative LiDAR Beach Survey; Development and Results P. J. Mumford University of New South Wales (02) 93854189 firstname.lastname@example.org G. Nippard University of New South Wales J. Middleton University of New South Wales E. Kearney University of New South Wales C. Cooke University of New South Wales I. Turner University of New South Wales M. Mole University of New South Wales The Airborne Science Initiative is a collaborative effort between the Department of Aviation, School of Surveying, School of Civil Engineering and School of BEES at the University of New South Wales. Harnessing the equipment and skills of the team, a series of beach surveys have been performed to gather data about beach dynamics over a period of six months. Long range weather forecasts have predicted that a major storm event will occur in 2011 with the development of a deep low pressure system in the Tasman Sea. Two beaches were chosen for the study; Narrabeen and Wamberal in an effort to document beach erosion before, after and during a major storm event. This paper documents the design of the system, the data flow and the analyses techniques used. Results of initial accuracy testing are provided, along with other results available at the time of writing. Finally, future development and missions are discussed. KEYWORDS: LiDAR, GPS/INS, beach, erosion, airborne mapping
Optimization-based In-flight Alignment for Airborne INS/GPS Navigation Yuanxin Wu National University of Defense Technology, P. R. China +86-0731-84576305-8217, email@example.com Xianfei Pan National University of Defense Technology, P. R. China +86-0731-84576305-8204, firstname.lastname@example.org The in-flight alignment is a critical stage for airborne INS/GPS applications. The alignment task is usually carried out by the Kalman filtering technique that necessitates a good initial attitude to obtain satisfying performance. Due to the airborne dynamics, the in-flight alignment is much difficult than alignment on the ground. This paper proposes an optimization-based coarse alignment approach using GPS position/ velocity as input. It is founded on the newly-derived exact velocity/position integration formulae. The alignment approach does not make any assumption on the inertial sensor and GPS position/velocity noise characteristics. Vehicle tests show that the optimization-based alignment approach is able to yield the initial heading angle, with less than 5 degree error in 10 seconds, less than 0.5 degree error in 70 seconds and less than 0.05 degree in 1000 seconds. It can serve as a nice coarse in-flight alignment stage for the subsequent fine Kalman alignment stage if other parameters such as sensor biases have to be estimated, or even act as a solo alignment stage if only the attitude estimate is concerned. The approach can also be applied to other applications that require aligning the INS on the run. KEYWORDS: In-flight alignment, INS/GPS, Kalman filtering, optimization
Validation of Interacting Multiple Model Estimator in Radar Tracking System Yu-Chun Kao Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: email@example.com Shau-Shiun Jan Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: firstname.lastname@example.org This paper focuses on the implementation and validation of the radar tracking smoothing algorithm. There is an optimal tracking smoothing algorithm called Multiple Hypothesis Tracker (MHT), but its computational complexity limits its practical application to radar tracking. Therefore, the Interacting Multiple Model (IMM) estimator is used in this paper which is a suboptimal hybrid filter. The IMM filter is one of the most costeffective hybrid state estimation schemes, and in this paper, an IMM filter is implemented by three parallel Kalman filters and then fuses the results according to their model probabilities. In general, a Kalman filter is an efficient algorithm of one exact inference by the linear dynamic system, but to utilize Kalman filter alone will fail to track the manoeuvre with highly nonlinear motion. In this paper, each Kalman filter is associated with a model based on the specific motion of an aircraft such as a straight line motion, turning motion and accelerating motion. The performance analysis of this IMM estimator is investigated with the simulation data and the real radar tracking data which was collected by Civil Aeronautics Administration (CAA), Taiwan. In the simulation process, a calibration procedure of the three dynamic models is developed in this paper, and their performance is evaluated by their positioning errors. In order to verify the manoeuvre tracking performance of the developed IMM filter, various simulated scenarios are implemented to validate the feasibilities of the calibrated model probabilities. Finally, this developed IMM filter is utilized to smooth the real radar tracking data recorded by CAA to validate its effectiveness in the real radar tracking system. KEYWORDS: Radar tracking; Interacting Multiple Model estimator.
Evaluation of APNT using ADS-B Radio Hou-Jen Chen Department of Civil Aviation, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: email@example.com Shau-Shiun Jan Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 70101, Taiwan Phone: +886-6-2349294 / email address: firstname.lastname@example.org In order to support the navigation service of the growing air transportation, Global Positioning System (GPS) has become the basis of the next generation Air Traffic Management (ATM) system in many countries. However, the signal of GPS may be weak that the ATM system is vulnerable under intentional or unintentional radio frequency interference (RFI). As a result, alternative position and navigation systems are necessary to maintain the ATM operation during GPS outages and to satisfy the safety requirements regarding to the aviation navigation service. The Automatic Dependent Surveillance-Broadcast (ADS-B) radio is a proper alternate because it is a part of Communications, Navigation, Surveillance and ATM (CNS/ATM) system developed by the Civil Aeronautics Administration (CAA) in Taiwan. ADS-B radio system constructs a mechanism that the aircraft and the ground stations broadcast the flight data to each other. Thus, this paper uses the time of the signal broadcast from the aircraft to the ground stations as the measurements of Time Difference of Arrival (TDOA) for the aircraft position. In this paper, two TDOA algorithms, which are Taylor-series Method and Chanâ€&#x;s Method, are evaluated. Unlike Chan's Method, Taylor-series method is sensitive to the transmitter-receiver geometry. For analyses presented in this work, the accuracies of the positioning results by two methods are evaluated by Mean Square Error (MSE) based on the Cramer-Rao Lower Bound (CRLB), Circular Error Probability (CEP), and GDOP methods. KEYWORDS: ADS-B; TDOA; APNT
POSTERS Poster 1 – A New Velocity Field From A Dense GPS Array In Southeastern Taiwan Horng-Yue Chen Associate Scientist/Institute of Earth sciences Academia Sinica/Taiwan 27839910 ext 417; 27839871;email@example.com Shin Tung Assistant Research/Institute of Earth sciences Academia Sinica/Taiwan 27839910 ext 516; 27839871;firstname.lastname@example.org Shui-Beih Yu Research Fellow/Institute of Earth sciences Academia Sinica/Taiwan 27839910 ext 416; 27839871;email@example.com In a 30 km x 20 km area of southeastern Taiwan, a dense GPS array composed of 10 CORS (Continuously Observation Reference Station) and 84 CMS (Campaign Mode Station) have been set up since 2001. The scientific goal of this array is to detect the crustal deformation and near-fault movement behaviors along the Longitudinal Valley Fault system. Position time series from a decade GPS observation is used to estimate the velocity for each station. A detailed near-fault deformation can be realized in the Luyeh area, Peinanshan massif, Taitung alluvial plain, and Coastal Range. With respect to Paisha, Penghu, the station velocities in the Coastal Range are 67 - 77 mm/yr in the directions of 308° - 321° and that in the Peinanshan massif are 44 - 67 mm/yr in 269°-307°, while the velocities are 29 - 34 mm/yr in 284°- 300 ° in the eastern margin of the Central Range. In the Taitung alluvial plain, the velocities are in the range of 39 - 52 mm/yr in 268 °- 286°. A significant discontinuity of about 32 mm/yr on the station velocities across the Longitudinal Valley Fault is observed as previous studies. However, more detailed features of near-fault movement are detected. KEYWORDS: CORS, CMS, Longitudinal Valley, near-fault deformation, station velocity.
Poster 2 - Applications Of Indoor Locating Technique Based On Various Types Of RFID C. C. Chang Department of Applied Geomatics, Ching Yun University, Taiwan firstname.lastname@example.org
The wireless communication technology is potentially applicable of providing spatial information to an indoor environment, and expected to effectively extend the locating areas from outdoors to indoors. One of such devices, namely the Radio Frequency Identification (RFID), was adopted to work with the in-house developed information system to investigate and implement its operation on indoor locating. It has been widely developed with a variety of RFIDs, including the passive, active, and radar types, for locating applications. A prototype of indoor guidance system, operated by pre-storing the spatial information into the tags attached on the decision points along the indoor paths, performs its locating function to find the ways and update the routing suggestions. Followed with the modelling to range estimation relied on the received signal strength, an indoor tracking system can provide the information of time, location, trajectory, speed, and alert message for the monitored objects. Moreover, a RFID-Radar system is applied to detect the targets‟ range and angle measurements and to decide their locations for inventory management. The graphical user interface is designed and provided to all the systems for an easy operation. The systems‟ architectures, tag contents, calculation algorithms, and function tests are comprehensively discussed. KEYWORDS: Radio Frequency Identification (RFID), indoor locating, guidance, tracking, inventory management.
Poster 3 - A Compressive Sampling Approach to Narrowband Interference Elimination for GNSS Chung-Liang Chang Department of Biomechatronics Engineering, National Pingtung University of Science and Technology No. 1, Shuefu Road, Neipu, Pingtung County, Taiwan, R.O.C. Tel: 08-7703202-7586 Fax: +886-8-7740420 email@example.com In this paper, the scenario where a modified compressive sampling algorithm acquires global navigation satellite system (GNSS) signal contaminated by an interfering signal is presented. Note that if the interfering signal exists in a known subspace orthogonal to the desired signal, the compressive measurements are projected into an orthogonal subspace and then the interference is nulled out. Besides, the interference cancellation method keeps the restricted isometry property (RIP) property of the sampling process which assures that distances between desired signals in the space are not influenced by the sampling process. Therefore, the state embedding of desired signal stays in the compressive domain and the proposed method remains robust in term of measurement noise and sampling non-idealities. The simulation result shows that the proposed method can enhance signal acquisition performance under the present of interference. It is shown that cancelling the interference in the compressive sampling process is helpful in subsequent signal acquisition in contrast to the fast Fourier transform (FFT)-based excisor approach. KEYWORDS: Compressive sampling; FFT; GNSS
Poster 4 - Dynamic Modelling for MEMS-IMU/Magnetometer Integrated Attitude and Heading Reference System Wei Li (1) 1. School of Electronics and Information/Northwestern Polytechnical University/China 2. School of Surveying and Spatial Information Systems/ University of New South wales/Australia Phone: 61- 404086982, firstname.lastname@example.org Jinling Wang(2) School of Surveying and Spatial Information Systems/ University of New South wales/Australia Phone: 61- 400463668, email@example.com Zhanrong Jing (3) School of Electronics and Information/Northwestern Polytechnical University/China Phone: +86 029 88492094, firstname.lastname@example.org
The MEMS based Inertial Measurement Unit (IMU) has a wide range of applications due to its low-cost, small size, and low power consumption. While their performance is affected by sensor noise, bias, and scale factor error, the traditional strap-down algorithm only using low-cost MEMS cannot satisfy the attitude and heading performance requirements. To achieve a long term stable solution, modern attitude and heading reference systems (AHRS) generally integrate IMU with other sensors, such as magnetometers. This paper has proposed a new dynamic modelling method for low-cost IMU and magnetometer integrated AHRS. In this method, the system dynamics model is based on the Psi-angle error equation. The acceleration residuals in North and East detraction and heading residual are chosen as the observation vectors, and the corresponding system observation model has been developed. Since the acceleration measurements would be affected by the dynamic acceleration of the system, the measurement covariance matrix is tuned adaptively according to the system dynamics to yield good estimates of the states. This proposed method for AHRS avoids the nonlinear problem, and consider the system dynamics sensed by the accelerometers to yield optimal performance. The experimental results show that the proposed method is a promising alternative for use in the AHRS. KEYWORDS: AHRS; IMU; MEMS; Adaptive Kalman Filter;
Poster 5 - Determination of Sudden Crustal Deformation by Earthquakes Su-Kyung Kim (1) Department of Geoinformation Engineering/Sejong University/South Korea Phone: +82-10-4115-4098, Email: email@example.com Tae-Suk Bae (2) Department of Geoinformation Engineering/Sejong University/South Korea Phone: +82-2-3408-3231, Email: firstname.lastname@example.org It is generally known that GPS baseline processing can precisely determine a user position at the level of sub-centimeter. The U.S. Geological Survey (USGS) announced that a magnitude of 9.0 Earthquake had occurred near the east coast of Japan on March 11, 2011, resulting in a displacement of the crust at the maximum of 2.4 meters. The Korean peninsula is located on the Eurasian tectonic plate that stretches out Japan, therefore, it is highly possible to be affected by the Earthquake. We processed the Korean GPS CORS network operating by NGII (National Geographic Information Institute) for 7 days before and after the Earthquake. The data processing strategy can be categorized by 1) Static baseline processing by fixing three IGS stations in China, Mongolia and Russia, 2) Static processing by fixing one of CORS network to verify the internal distortions of the network, 3) Kinematic processing in order to check the possibility of detecting the signals. All data processing was carried out using Bernese V5.0 with IGS precise orbit. The test results show that most of the parts in Korean peninsula has moved to the east, ranging 2.6 to 5.8 cm, compared to the final solution for the day before the Earthquake. The static processing has an agreement with the precise point positioning (PPP) solution in the horizontal displacement. The stations, such as DOKD, ULLE that are established on the islands closer to the epicenter, have clearly moved the largest amount. On the contrary, the station JAHG located on the southwestern part of Korea presents relatively small variations with slightly different direction. The relative positioning between CORS confirms internal distortions of the Korean peninsula. In addition, the kinematic processing of CORS data with 30-second interval gives an indication of Earthquake signals with a latency of about 5 minutes depending on the distance from the epicenter. It should also be verified by processing a long-term data and the kinematic processing of high-rate data such as 1 Hz. KEYWORDS: Earthquake, GPS, Crustal deformation, Kinematic processing
Poster 6 - The RAIM Based Airborne Ionosphere Anomaly Monitoring Algorithm Using the Differential Hatch Filters Jungmin Joo (1) Satellite Navigation Department/Korea Aerospace Research Institute/South Korea Phone: +82-42-860-2554 Fax: +82-42-860-2789 Email address: email@example.com Jeongho Cho (2) Satellite Navigation Department/Korea Aerospace Research Institute/South Korea Phone: +82-42-860-2407 Fax: +82-42-860-2789 Email address: firstname.lastname@example.org Moonbeom Heo (3) Satellite Navigation Department/Korea Aerospace Research Institute/South Korea Phone: +82-42-860-2266 Fax: +82-42-860-2789 Email address: email@example.com Ground Based Augmentation System (GBAS), such as the U.S. Local Area Augmentation System (LAAS), augment satellite navigation system by providing differential corrections and integrity information to aviation users to provide precision approach for aircraft landing at airports. However, because the current Category-I GBAS architecture uses only single frequency signal, the current architecture may not be able to meet GBAS performance requirements under the large ionospheric gradients because of spatial ionospheric decorrelation between the GBAS ground station and aviation users. During ionospheric storms in October and November 2003, these severe problems were happened. Several previous signal or measurement quality monitoring algorithms take longer time than Time-to-Alert requirement to detect ionosphere anomalies in a certain worst case and occasionally happen to alert in spite of the small position error. In this paper, we propose a RAIM based airborne monitoring algorithm using the differential Hatch filters for ionosphere anomaly detection in position domain to detect more quickly and accurately. While the current GBAS system is based on carrier smoothed code phase differential processing using the Hatch filter, the proposed detection technique is designed to be able to detect a significant gradient in the ionosphere by comparing the position error between the airborne and the ground station with double different time constants for the Hatch filters respectively. In simulation results, it demonstrated that the proposed scheme is capable of detecting ionosphere anomaly in worst case in 4 seconds. In addition, it showed appropriate threshold decision architecture for the monitor followed by availability performance analysis. KEYWORDS: GBAS; RAIM; Ionosphere anomaly detection; Differential Hatch Filters; Time-to-Detection
Poster 7 - Enhanced time transfer of Loran-C by temperature compensation Chang Bok Lee KRISS/ Center for Time and Frequency/South Korea 042-868-5140/042-868-5287 firstname.lastname@example.org Sung-hoon Yang KRISS/ Center for Time and Frequency/South Korea 042-868-5147/042-868-5287 email@example.com Young Jae Kim KRISS/ Center for Time and Frequency/South Korea 042-868-5232/042-868-5287 firstname.lastname@example.org Sang Jeong Lee Chungnam National University /Department of Electronic Engineering/South Korea 042-821-6582/042-823-4494 email@example.com In recent the GPS is the most popular in the field of the timing application. However, as we known, it has weak point to be easily affected by jamming. Therefor most of GPS users have a redundancy system in mind for reliable system. Republic of Korea has been operating the two long range navigation (LORAN) stations, so we have studied on the method of enhanced time transfer by Loran-C as a domestic timing reference. We found that the time transfer results by Loran signal is changing by environmental temperature. In order to compensate its influence, we utilized the temperature data which had been measured the day before. In this paper we present how to reduce the effect by it and report the results by the technique. KEYWORDS: Time transfer, Loran, Time accuracy, Temperature compensation
Poster 8 - A TDOA Based BLUE for a 3-D Localization Young Kyu Lee Korea Research Institute of Standards and Science, Korea Phone: +82-42-868-5569, Fax: +82-42-868-5022, firstname.lastname@example.org Sung Hoon Yang Korea Research Institute of Standards and Science, Korea Phone: +82-42-868-5147, Fax: +82-42-868-5022, email@example.com Chang Bok Lee Korea Research Institute of Standards and Science, Korea Phone: +82-42-868-5140, Fax: +82-42-868-5022, firstname.lastname@example.org In this paper, we derived a closed-form equation of a best linear unbiased estimator (BLUE) and its minimum variance for the estimation of the location of the emitter based on the time difference of arrival (TDOA) technique. The minimum variance is the same as Crammer-Rao lower bound (CRLB) when the noise has the Gaussian probability density function. They are derived for the case of estimating 3dimensional position of the emitter with 4 receivers or sensors, and for this purpose, we used an approximated equation of the TDOA hyperbola equation obtained from the first order Taylor-series after setting the reference points of the position. The derived equation can be used for any kind of noises which are uncorrelated in each other in the TDOA measurements and for a white Gaussian noise also. KEYWORDS: Location Estimator, TDOA, CRLB, Taylor series, BLUE.
Poster 10 - Acquisition Complexity Reduction by Multi-stage Partial CrossCorrelation Technique for GPS Receiver Jae-kil Kim Department of Information Communications Engineering / Chungnam National University / South Korea Tel : +82-42-821-7796, Fax : +82-42-826-5586, email@example.com Jeong-been Kim Department of Information Communications Engineering / Chungnam National University / South Korea Tel : +82-42-821-7796, Fax : +82-42-826-5586, firstname.lastname@example.org Jae-Min Ahn Department of Information Communications Engineering / Chungnam National University / South Korea Tel : +82-42-821-7796, Fax : +82-42-826-5586, email@example.com A new acquisition technique based on delay-multiply correlator followed by multi-stage Doppler frequency shift acquisition for Global Positioning Satellite (GPS) signal is proposed. By applying the delay-multiply correlator, the code phase acquisition becomes independent to the Doppler frequency shift and the
acquisition complexity could be reduced to 1-dimensional search. However, to demodulate the navigation message, the Doppler frequency shift should be estimated and compensated during the acquisition process of the GPS signal. At first, the proposed scheme acquires the code phase with the delay-multiply correlator, and then estimates the Doppler frequency shift with partial cross correlation technique. By applying the delay-multiply technique to the partial cross correlation values, the Doppler frequency shift could be estimated and compensated. The Doppler frequency shift estimation using partial cross correlation should be performed with increased partial cross correlation length to reduce the remaining frequency shift, that is, multi-stage correlation and compensation. The proposed acquisition technique for the GPS signal could greatly reduce the complexity of GPS receiver. KEYWORDS: GPS, Acquisition, Doppler shift, Delay and Multiply Approach
Poster 12 - Impact of the Yaw Modeling on the Precision GPS Orbit Determination Tae-Suk Bae (1) Dept. Geoinformation Engineering/Sejong University/South Korea +82-2-3408-3231(T), +82-2-3408-4341(F), firstname.lastname@example.org Su-Kyung Kim (2) Department of Geoinformation Engineering/Sejong University/South Korea Phone: +82-10-4115-4098, Email: email@example.com The dynamic modeling is generally used for the determination of the precise GPS orbit by numerically integrating the accelerations acting on the satellite. The GPS Block II/IIA satellites have the antenna offsets from the center of the mass in the direction of both X and Y axis of the satellite body-fixed frame. These offsets affect the satellite attitude as well as the positioning accuracy, especially in the case of PPP (Precise Point Positioning). The satellite attitude is difficult to model in noon and midnight turns. Therefore, many analysis centers exclude the GPS measurement during the eclipse including the recovering period after shadow-crossing. Kouba (2009) developed a simplified yaw-attitude model consistent with the original one (Bar-Sever, 1996). New model is incorporated and tested in the orbit integrator, called ORB, which is a collaboration with the NGS (National Geodetic Survey). The numerical accuracy of the bi-directional multistep integrator is at the level of sub-micrometer level at GPS altitude. All dynamic accelerations caused by the geopotential, the third-body such as the Moon and the Sun, are combined together for the integration. The remaining forces are modeled as the empirical parameters at the frequency of once-per-revolution. The integrated orbit is compared with the published IGS precise orbit in inertial frame. Consequently, it can be noticed that there is an impact of the yaw attitude modeling on GPS orbit during the eclipse season. These should be combined with the PPP software to verify the positioning accuracy in the future. KEYWORDS: GPS, Orbit, Yaw modeling, Numerical integrator.