E5fe258348be30eab6f5e1950fb8887c

MAPPING OF MALDIVES USING AERIAL PHOTOGRAPHY AND DIGITAL PHOTOGRAMMETRIC TECHNIQUES V. Raghu Venkataraman*, K. Kalyanaraman, Dr. K. Radhakrishnan, Dr. R.R Navalgund, P. Srinivas*, PVSSN Gopalakrishna, CVKVP Jagannadha Rao, K. Srinivasa Rao, G. Srinivas,

P. Shashivardhan Reddy, J. Narendran, CS Narsimham, Dr. K. Venugopala

Rao.

AERIAL SERVICES & DIGITAL MAPPING AREA National Remote Sensing Agency, Department of Space, Govt. of India, Balanagar, Hyderabad – 500037, India

Corresponding author 1

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P. Srinivas

e-mail: srinivas_p@nrsa.gov.in National Remote Sensing Agency, Department of Space, Govt. of India, Aerial Services & Digital Mapping Area, Balanagar, Hyderabad – 500 037 Andhra Pradesh, INDIA Telephone Nos. 0091 040 23884489 (O) Fax No. 0091 040 23884483 Corresponding author 2

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V. Raghu Venkataraman e-mail: raghu_vv@nrsa.gov.in Telephone Nos. 0091 040 23884470/71 (O)

Abstract Republic of Maldives is located in the Indian Ocean about 300 miles south of India and 450 miles south west of Sri Lanka consisting of 26 atolls with 1192 islands scattered between 1ยบ S to 8ยบ N latitude, 72ยบ E to 74ยบ E longitude with 99 % of the area being water.

The objective of this project was to prepare digital maps of the entire country in 1:25,000 scale using aerial photographs acquired in 1:40,000 scale in a single coordinate system. Remote sensing satellite data was acquired for preliminary reconnaissance of the terrain and selection of reference and base stations for continuous Global Positioning System (GPS) observations to establish reference datum in WGS 84. Thereafter, flight operations for aerial photography were carried out with automated Computer Controlled Navigation System (CCNS).

Digital photogrammetry techniques with Kinematic GPS data and pre pointed GPS control survey data was utilized for aero triangulation, block adjustment and vector capture.

The large scale mapping for 16 select islands of Maldives was carried out in 1:1000 scale using 1:6000 scale aerial photographs.

Keywords: Aero triangulation, Digital photogrammetry, GPS, Reference station, CCNS.

1. INTRODUCTION The Republic of Maldives consists of an archipelago of 1192 islands scattered over a distance of 870 km in the North–South direction and about 150 km in the East-West direction between 0º42’30”S to 7º6’30” N latitude, 72º32’30” E to 73º46’15” E longitude. It is located in the Indian Ocean about 480 km South of India and 725 km South West of Sri Lanka.

The islands are grouped in the form of atolls. An atoll is a coral island consisting of a circular belt of corals enclosing a central lagoon. Maldives consists of 26 atolls. The atolls and islands are scattered and spread across an area of 100 000 sq. km. area, 99% of which is water and less than 1% covers land portion. Only 33 islands have a land area of more than 1 sq. km and one third of all the inhabited islands have fewer than 500 people.

Earlier, different organizations have attempted and prepared very small scale maps for navigation but large scale maps of atolls and islands could not be prepared due to non availability of appropriate technology. With the advent of Global Positioning System (GPS) and photogrammetry techniques coupled with stereo aerial photography the potential for digital mapping in a single reference frame work was realized through a collaborative project between the Government of India (GoI) and the Republic of Maldives.

This paper attempts to provide a comprehensive picture of the methodology, technology and processes involved in the execution of the project by the National Remote Sensing Agency (NRSA), Hyderabad an organ of the Department of Space (DOS), GoI.

2.

BACKGROUND

In 1999, Honorable Mr. Ibrahim Hussein Zaki, Minister for Planning and National Development, Government of Maldives had discussions with the High Commissioner of India, Hon’ble Mr. Kanwar Singh Jasrotia regarding the possibility of digitally mapping the archipelago and establishing of a remote sensing unit in his country. Thereafter the Maldivian authorities sent a request for this purpose. The GoI responded to this request with a project proposal which was shared with the Maldivian authorities.

The President of Maldives H.E. Mr. Maumoon Abdul Gayoom, during the state visit to India in August, 2000, had evinced keen interest in the work carried out by NRSA and requested follow up action on the above mentioned project proposal.

Based on the request from the Maldivian authorities, The Ministry of External Affairs (MEA), GoI approached DOS and asked for a detailed project proposal for consideration by both the Governments. Accordingly the project proposal was prepared by NRSA for further consideration and implementation.

3.

PROJECT OBJECTIVES

NRSA was awarded the project “Digital Mapping of The Republic of Maldives� by the MEA. The project consisted of:

3.1

Preparation of digital maps on 1: 25 000 scale using 1: 40 000 scale aerial photographs for entire Maldives in a single reference frame with Universal Transverse Mercator (UTM) coordinates.

3.2

Preparation of digital maps on 1: 1 000 scale using 1: 6 000 scale aerial photographs for 16 selected islands.

3.3

Establishment of a Remote Sensing Centre at Male, Maldives

4.

AVAILABILITY OF MAPS

It was reported that metric charts of Maldives published in 1993 covering the whole of Maldives on a scale of 1:300 000 were available as given below:



Maldives Sheet 1 : Addu Atoll to North Huvadhoo



Maldives Sheet 2 : North Huvadhoo Atoll to Mulaku Atoll



Maldives Sheet 3 : Mulaku Atoll to South Maalhosmadulu Atoll



Maldives Sheet 4: South Maalhosmadulu Atoll to Thavndhippothu Atoll.

These charts are the updated version using aerial photos taken by Royal Air Force (RAF) of UK in 1968 and 1969 and satellite imagery acquired between 1984 and 1988. These 1:300 000 charts were of not much of use to for detailed development planning as the Islands of Maldives are very small, ranging from 0.5 sq. km. to 2 sq. km. In addition, 8 sheets on 1:250 000 scale based on UTM projection were also available, but these maps also lacked much of the required details in terms of size and land area of the islands.

In the course of execution of this project, the 4 th edition of the “Atlas of the Maldives”, (ISBN 1 876410 42 6) published in 2004 by Atoll Editions, PO Box 113, Apollo Bay, Victoria, 3233, Australia was extensively used as a reference document.

5.

METHODOLOGY

The methodology for the preparation of digital maps (Paul R. Wolf and Bon A. Dewitt) on 1:25 000 scale and 1:1 000 scale involved the following processes as indicated in Fig. 1 and Fig. 2 respectively.

5.1

Flight planning of aerial photography operations.

5.2 Aerial Photography in 1: 40 000 scale and 1: 6 000 scale (for few selected islands) with Kinematic GPS (KGPS) observation

5.3 GPS observations on Reference stations (13 Nos.) and pre-targets (41 Nos.) of size 5m x 5m for establishment of reference frame in WGS 84 datum for entire Maldives

5.4 Processing of aerial exposed film rolls & annotations of processed film rolls at Photo processing lab at NRSA.

5.5 Ground control survey for few selected islands on 1: 6 000 aerial photographs

5.6 Post processing of airborne Kinematic GPS data and static GPS reference stations and other ground control points.

5.7 Scanning of aerial film rolls using precision photogrammetric scanner @ 21 microns for 1: 40 000 scale aerial photographs and @ 20 microns for 1: 6 000 scale aerial photographs.

5.8 Aero triangulation (densification of ground control points) using softcopy / Digital Photogrammetry systems.

5.9 Digital Mapping on 1: 25 000 / 1: 1 000 scale using Photogrammetry systems for plotting and subsequent use in Geographic Information System (GIS) environment.

5.10

Field verification / data collection for few selected islands and other atolls on 1: 1 000 scale and 1: 25 000 scale map sheets respectively.

5.11

Quality control of digital maps

6.

RATIONALE FOR METHODOLOGY FOR 1:25 000 SCALE MAPS

The methodology for mapping in 1:25 000 scale was arrived at based on the required map content and need to have a country wide coordinate system.

6.1

Requirements

The most challenging requirement was of course the need to have a single grid coordinate system for the entire country.

As regards content, essentially the 1:25 000 scale maps had to show the extent of the land area in terms of both shape and size clearly demarcating the land and water boundary, atolls, built up areas, roads, and vegetation.

As regards coordinates and projection, the need was to accurately depict the position of the islands in the country wide grid. This would automatically give the positions of the islands relative to each other and the distances between them.

6.2

Data sources

B & W stereo aerial photography in 1:40 000 scale was selected as the primary data source because it would provide a spatial resolution of about 100 cm which is adequate for demarcating the required content layers. The option of utilizing high resolution satellite data with 100 cm resolution was also thought of but discarded since the data comprising of about 800 scenes of entire 100 000 square km area would have to be sourced as the frame sizes are normally of 10 km x 10 km size. Aerial photography provided the twin advantage of economic

and selective data acquisition covering only those areas where the proportion of land was significant as well as providing stereo data for generation of height information. RMK 15/23 camera was selected as it would provide metric quality photographs with wide swath to reduce overall flying time.

For the purposes reconnaissance for aerial photography and GPS based control survey, LISS III sensor imagery of IRS 1C-1D was selected as the imagery with a resolution of 23 m and in color clearly show the relative positions of the islands along with the shape and size of the islands.

Since it would be virtually impossible to get required controls using traditional methods due to the vast expanses of water the only option was to use GPS controls. The GPS points were pre-signalized so as to be able to be identified on the aerial photos.

To derive full benefit of the availability of Kinematic GPS data for the aircraft platform for initial estimation of the frame centre coordinates.

6.3

Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form using high quality photogrammetric scanner.

It was also decided to utilize digital photogrammetrc techniques for aero triangulation and block adjustment since analytical systems were obsolete and a certain level of automation was inherently available for point selection.

Once the primary data is oriented in such to the correct direction and block adjustment completed, the process of vector capture in the mapping environment, comprising of PC based low cost systems, was selected for yielding the line maps with appropriate symbols so that multiple systems could be deployed.

7.

7.1

RATIONALE FOR METHODOLOGY FOR 1:1 000 SCALE MAPS Requirements

The main requirement was content. 1:1 000 scale maps had to show each individual building and built up features very clearly along with the land area utilized and the distances between features have to be accurate within 25 cm besides the extent of the land area in terms of both shape and size.

7.2

Data sources

B & W stereo aerial photography in 1:6 000 scale was selected as the primary data source because it would provide a spatial resolution of better than 10 cm which is adequate for demarcating the required content layers. Stereo data was critical for accurately mapping buildings.

To derive full benefit of the availability of Kinematic GPS data for the aircraft platform for initial estimation of the frame centre coordinates.

7.3

Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form using high quality photogrammetric scanner.

It was also decided to utilize digital photogrammetric techniques for aero triangulation and block adjustment since analytical systems were obsolete and a certain level of automation was inherently available for point selection.

8. FLIGHT PLANNING Flight planning was an important and critical component for this project since most of the area is covered by water. Information from various sources such as satellite images, existing atlas maps of Maldives, old maps etc., was used to prepare optimized flight plans so as to make flying economical and minimize wastage of both flying time and aerial film. This was especially critical as the window of opportunity comprising of cloud free season over the area is extremely limited. The imagery from LISS-III sensor of Indian Remote Sensing Satellites (IRS 1C/1D) for the entire area was used for preliminary reconnaissance and flight planning. The above IRS imagery were also utilized for identification of suitable locations for the GPS reference stations and Ground Control Point (GCP) pre signalized targets in an economical manner. The World Wide Mission Planning (WWMP) software was used for flight planning.

The entire country was divided into seven geographical blocks for planning, managing and execution of the project as shown in Fig. 3 for aerial photography in 1: 40 000 scale. The runs were planned for some blocks in N-S direction and for some blocks in E-W direction depending on the shape of the block. Besides the main runs, tie lines were also planned for each block in oblique direction.

Since the land portion was less the number of tie lines planned was much more than in normal situations. The intersection of main lines and tie lines in the flight plan was made in such a way as to fall in as many islands as possible.

The details of the flight plans are given below in Table 1

9.

AERIAL PHOTOGRAPHY OPERATIONS

Aerial photography (Black & White) was carried out using Beech Super King Air B-200 (Fig. 4) mounted with Zeiss RMK15/23 metric camera and integrated with INS and Kinematic GPS. The aircraft is guided by Computer Controlled Navigation System (CCNS) software for carrying out aerial photography very accurately. The camera is tightly coupled with CCNS that in turn connected to airborne GPS.

After interactive checks and corrections of the software-generated flight lines, the data is stored on a PCMCIA card. The aircrew was also provided with this flight planning information in hard copy form. During aerial photography this data is transferred to the on board computer. The aircraft navigation is carried out with the assistance of CCNS4, which is supported by GPS a satellite navigation system. At the precise moment that an aerial photo is exposed, the position of the aircraft can be determined by evaluating the signals from, at a minimum, four satellites. In addition to computer controlled navigation, aircraft position at the precise moment of shutter release can be determined by a ground station using Kinematic GPS (KGPS). After completion of aerial photography, the recorded coordinates of the camera’s projection centres are read into Bentley’s MicroStation CAD software using a standard interface and then plotted out as flight line indices.

The CCNS is a guidance, positioning and management system for aerial survey flight missions. The basic system consists of the Central Computer Unit (CCU), the 5'' TFT Command and Display Unit (CDU), and necessary cabling and mounting. Optional equipment completes the system to fulfill specific requirements. The system is universally usable and can operate and integrate all Wild/Leica, Zeiss respectively. Z/I Imaging aerial camera systems. It provides a complete and comprehensive solution for mission planning and documentation, aircraft guidance and sensor management during missions. CCNS controls the camera and other sensors, including crab/drift setting(s), forward overlap, V/H computation and provides data for data annotation on film; the co-ordinates may be WGS84 or the countries X/Y co-ordinates (optional).

The CCNS brings the advantages of a glass cockpit and a fully automated flight control system to aerial surveying and reconnaissance. All operations are activated via one knob and four buttons. The EFIS type display, which is operated like an aircraft instrument, is divided into guidance and system/sensor management information (right side of the display). The pilot just has to "follow the needle". Outputs, with selectable sensitivity for HSI, VDI and CDI instruments, are provided.

The camera used in this project is RMK aerial survey camera System. It features a systematic, modular design with individual components forming logical functional units optimized for both practical application and economical use. The

RMK features high-performance lenses with internal filters, which significantly enhance image quality and a unique pulsed rotating-dish shutter. It is Ideal for GPS/INS - supported navigation and aero triangulation. It also has eight pointshaped fiducials in the corners and midway along the edges, numbered 1 to 8, spacing 113 mm, point diameter 100 Âľm, cross lines with 50 Âľm line thickness, exposed at midpoint of exposure.

The flight operations were carried out during the month of February, 2004 as that was the ideal cloud free season over Maldives. Aircraft was ferried from Hyderabad to Male via Trivandrum. Permission from the Director General of Civil Aviation (DGCA), GoI was taken prior to departure as per the regulations for ferry flight to Male without licensed Navigator and for YA number was YA/N 538/01/30094. Civil Aviation Department of Maldives issued clearance letter to Maldives airports authorities for entry into Maldivian airspace vide Permit no. is CAD-VRMM/LP-IEXT/04/32.

The aircraft was mobilized only with crew, maintenance engineers, equipment and film. Camera system engineers, GPS survey team and coordinators were mobilized via civil airlines.

After the flight planning was completed hard copy print outs were taken for reference. Two PCMC cards with flight planning data were provided for loading on to the aircraft CCNS which was loaded and checked prior to departure.

Aircraft readiness was also checked at the base. The SKA B-200 aircraft has a mandatory 100 hour inspection to be carried out at base with hanger and stores facility. The volume of flying effort involved in terms of flying time was carefully estimated including main ferry, local ferry, actual operations and alignment/ turn times. This was optimized to approximately 95 hours by avoiding water areas so that the aircraft could mobilize to Maldives after 100 hour inspection at Hyderabad and complete the entire task without having to interrupt for coming base to base for inspection. To ensure snag free performance spare tyres and

A total of 25 film rolls of 240 mm format each having a capacity of exposing 275 frames was drawn from the refrigerated stores and loaded into the aircraft for mobilization. At Male the film rolls were unloaded and kept in a safe custody in air-conditioned environment to prevent degradation of film due to heat.

Aerial photography operations were carried out from Male international airport as the base. Sorties were carried out in such a manner that the local ferries were made productive for tie lines.

10. GPS SURVEYS 10.1

Reference stations

Thirteen GPS reference stations spread over the entire Republic of Maldives in different blocks for the project were used for airborne GPS assisted aerial

photography for the establishment of reference network (Sapporo, July 2003 & Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998 ) in WGS-84 and pretarget GCPs in tandem as shown in Table 2. The reference stations were located in such a way that at least one reference station was there in one-degree grid.

Each reference station was occupied with geodetic grade dual frequency GPS receivers for a minimum of three days for duration of 12 hours from 6 AM to 6 PM every day. The Male International GNSS Services (IGS) station was also occupied as part of this GPS campaign. A permanent monument was established at each reference station site.

10.2

Pre-target base stations

Forty two pre-target GCPs spread over the entire country were installed in place and GPS survey of the points was carried out as shown in Table 3. The pretarget GCP designed was 5m X 5m in dimension with plus mark in white and remaining quadrant area in black as shown in the Fig. 5. Each pre-target GCP was occupied continuously with a geodetic grade GPS receiver for duration of 3 hours simultaneously with the GPS reference station as shown in the Fig. 6.

The land area of Republic of Maldives is spread over 100 000 Sq. Km. The planning of aerial photography, deployment of personnel for reference station operations and pre target surveys involves meticulous planning, coordination and implementation of the plan. Most of the islands in Maldives are uninhabited and locating natural and man-made features are next to impossible, hence pre signalization was carried out before the aerial photography. The major portion of

the country is covered with water and the numbers of airports were less, hence deployment of personnel at different GPS locations by traveling very long distance on open sea was an Herculean task. The following map as shown in the Fig. 7 depicts the planning carried out in the deployment of the personnel at different GPS sites.

10.3

GPS Data processing

The GPS data pertaining to the reference station is processed in a Bernese scientific post processing software, which is capable of processing long baselines and the coordinates of the reference stations are computed using the GPS data from the nearest IGS stations namely Bangalore (India), De Garcia (Indian Ocean), NTUS (Singapore), Bahrain etc. The coordinates of Pre-targets was derived by processing the GPS data collected at Pre-targets with reference to the nearest reference stations using SKIPRO software in differential mode.

11.

PATH RECOVERY, SCANNING OF AERIAL PHOTOGRAPHS, AERO TRIANGULATION AND BLOCK ADJUSTMENT

The path recovery of aerial photographs was a Herculean task. It involved retrieving the aerial photos as per the planned flight plans and recee reports (prepared by pilots on the day of aerial photography). Since 99% of the entire Republic of Maldives is covered with water, identifying and segregating of aerial photographs as per the recee report and flight plans was a very difficult task. This was very important to reduce the volume of effort in scanning of the aerial photographs.

The scanning of aerial photographs was carried out using very high precision Zeiss SCAI Photogrammetry scanner and aerial photographs in 1: 40 000 scale were scanned at 21 microns. The scanning was executed very carefully by applying enhancements since the terrain was very difficult and sun light was varying from one part of the atoll to another. The pre-targets placed on the ground were identified as shown in Fig. 8 and checked with the flight plan. Thus only 2377 out of the total 4456 frames representing 53 % of the frames were scanned. At an average daily productivity of 20 frames per day, this optimization resulted in saving about 100 days in the time schedule. These digital images were used for automatic aerial triangulation and block adjustment.

Triangulation is defined as the extension or densification of control within the block. Block adjustment depends on the distribution of GCPs, quality of GCP, type of terrain, quality of image (for generation of tie points by image matching) and the proper analysis of the block. The sigma defines the accuracy of the block

The scanned aerial images were input to the aero triangulation along with camera calibration report, processed DGPS data and processed KGPS data.

Triangulation was carried out using high-end Photogrammetry system consisting of Socetset software along with Orima block adjustment software. Automatic aero triangulation with an autonomous batch process by selecting pre-selected tie points and appropriate matching strategy was used in this project. Aero

triangulation was performed with different strips composed of both parallel and cross strips covering seven blocks. Utilization of Digital Photogrammetry Work Station (DPWS) with automation in triangulation and bundle block adjustment had reduced the processing time and expensive manpower otherwise required for analytical aerial triangulation. The project file was set up in Socetset with all the scanned images and calibration parameters such as calibrated focal length, fiducial mark coordinates, Principle Point coordinates, radial distortions etc.

Automatic IO was carried out in batch mode by image correlation with the fiducial templates available for RMKTOP camera.

The use of GPS derived antenna positions during the photo acquisition had considerably improved the performance of the aerial triangulation process as well as reduced the number amount of ground control points in the field (C.S.Fraser, 1994). Since the land portion is 1% of the total extent of the Maldives, enough GCPs (pre-targets) could not be placed. The exposure coordinates of each frame was taken as primary control and given more weight age for the block adjustment as compared to the Pre-target GCPs. The ground control points used for the block adjustment were the pre-targets, reference stations and processed KGPS data.

The other inputs for this project such as camera calibration file, flight plan index, overlaps, image scale and image sequences were used for initial approximation of the block. GPS camera stations are used for the stabilization of the block. The

results of block adjustment are based on the average image precision measurement of 0.5 to 1 pixel.

The triangulation of aerial photographs in 1: 40 000 scale was carried out for individual blocks as shown in the Fig. 3. However for aerial photographs in 1: 6000 scale, the triangulation was carried out island wise and adjusted accordingly. The GCPs were acquired by our team for selected islands in the difficult terrain conditions. The nearest reference station was taken as the base station and the GPS survey was carried out in the same coordinate system reference schema. The results of aerial triangulation for all the blocks are tabulated as shown in the Table 4.

12.

REFERENCE GRID

A reference grid has been designed for covering the entire Maldives with 1:25 000 scale maps. The reference grid is in UTM projection. The grids are of 10 000 m (10 km) interval. The Latitude and Longitude values are also available in Degrees, Minutes & Seconds for which the gridlines are drawn for 1 degree, 15 minutes and 7 ½ minutes intervals.

The numbering schema for the entire Maldives on 1: 250 000, 1: 50 000 and 1: 25 000 scale maps are shown in Fig. 9, Fig. 10 & Fig. 11 respectively. The numbering schema derived for 1: 25 000 scale maps is as per the International Map World (IMW) series. In Maldives most of the area is in northern hemisphere above the equator and a small portion part of the area falls in southern Hemisphere, below the equator. To have positive coordinate value in North direction, the origin was shifted to the Southern Hemisphere. The zone number 43 (Southern hemisphere) was taken for processing the GPS coordinates with UTM projection. The datum (vertical reference) for the mapping is with respect to WGS 84.

13.

LAYER LIST

The data is captured in different layers as per the feature (layer list), which aides in importing the data into GIS environment. The list of maps in 1:25 000 which actually cover land or atoll portion (no deep waters) is as given below as shown in Table 5. List of islands for which 1:1 000 scale maps were prepared and are listed below in Table 6. The layer list used for the preparation of maps in 1: 25 000 scale for entire Republic of Maldives & 1: 1 000 scale for selected islands are listed in the Table 7.

14.

GIS DATABASE

Maldives GIS database has been created at 1:1 000 scale and 1:25 000 scale using object oriented technology with open GIS standards in ArcGIS environment. In order to have compatibility with base maps in AutoCAD format, the GIS data models were developed with same spatial reference system including datum, projection and spatial extent.

To facilitate nation wise as well for island wise GIS applications such as censes, utilities (water supply, sewerage, gas, communication, power, environmental, agriculture, fisheries, navigation, national security, transportation) and revenue a seam less GIS data model was developed.

Keeping GIS database volume and optimization, it is proposed to develop the data structures as personal GIS geodatabase, which uses the Microsoft access to store the both spatial and non-spatial database. The developed GIS database can be scalable to enterprise GIS database using Relational Data Base Management (RDBM) software like oracle, once the GIS applications developed over this as mentioned above.

15.

ESTABLISHMENT OF REMOTE SENSING LAB AT MALE

The establishment of Remote Sensing Centre at Male, Maldives involved the following: 15.1

Procurement of digital image processing system, digital photogrammetry system, GPS receivers & GIS system.

All the hardware and software

modules were tested at NRSA.

15.2

Training of personnel of Maldives for the period of 4 to 6 weeks at NRSA. This phase of training was carried out in November / December 2004 for 4 Maldivian officials

15.3

Submission of digital maps. The final maps including orientation files, images etc has been copied in the systems at Maldives and NRSA officials had demonstrated the usage of the maps for different applications.

15.4

Installation of systems at the full fledged remote sensing unit with all the hardware and the software as shown in Table 8 at Male, Republic of Maldives during April 2006 with on site training on the systems with the populated with digital maps.

16.

CONCLUSIONS

The aerial photography along with the establishment of reference datum in WGS84 was carried out for the first time for entire Republic of Maldives. Mapping in 1: 25 000 scale for entire Maldives and large scale mapping in 1: 1000 scale for a few selected islands are the landmark. The whole task including the establishment of remote sensing centre at Male was completed within the stipulated project time as planned and the timeline for the individual activities is as shown in Fig. 12.

17.

ACKNOWLEDGEMENTS

We acknowledge our sincere thanks to the DOS, GoI for giving us the opportunity to take up this project. We also acknowledge our thanks to MEA for funding and awarding the project to DOS.

We extend our sincere thanks to Dr. RR Navalgund, Director SAC who had extended his full support in planning and executing the project in his capacity as Director, NRSA. We also extend our warm thanks to Director, NRSA Dr. K. Radhakrishnan for his guidance in establishing a remote sensing centre at Male, Maldives.

We acknowledge the contribution of all the other personnel involved in the project mainly (i) pilots Capt. AL Hannurkar and Capt SMH Mehdi, (ii) Navigator Wg. Cdr. (retd) Dalbir Singh, (iii) Aircrew engineers, field survey personnel and photogrammetrists Shri B. Laxman, Mrs. I Jayalakshmi, Shri P. Krishnaiah, Shri

B. Sadasiva Rao, Shri Anantha Padmanabha, Shri M. Sreedhar, Shri NMS Reddy, Shri D. Syama Rao, Shri G. Anil Kumar, Shri Y. Srinivasa Rao, Mrs. M. Udayalakshmi, Mrs. TE Rani, Shri P. Srinivas Reddy, Shri G. Devender Rao, Shri K. Krishna and Shri Ashutosh Bharadwaj.

18.

REFERENCES



Paul R. Wolf and Bon A. Dewitt, Elements of Photogrammetry



Sapporo, The Royal Thai Survey Department - A report on the Geodetic work (1999 – 2002) at the XXIII General Assembly of the International Union of Geodesy and Geophysics during 30 June – 11 July, 2003.



Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998 , Establishment of a GPS High accuracy Reference Geodetic Network in the Caribbean, Surveying and Land Information System, Vol. 58, No. 1, 1998, pp 13-24.



C.S.Fraser, - GPS Aerotriangulation – in sights from Angledool project., Aust .j.Geod. Photogram.Surv, No.61, December, 1994, pp 1 – 16.

List of Tables Table 1:

Flight Plan Details for 1:40 000 scale photography

Table 2:

GPS Reference Station for Airborne GPS

Table 3:

GPS Reference & Target / Rover Stations

Table 4:

Results of Aerotriangulation of entire Maldives shown as blockwise

Table 5:

List of maps for entire Maldives in 1: 25 000 scale

Table 6:

Name of the selected islands in 1: 1 000 scale

Table 7:

Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping

Table 8:

List of hardware and software established at Male, Maldives

Table 1 Flight Plan Details for 1:40 000 scale photography Block Number

Number of Main Run lines and direction

No. of tie lines

Approx. number of frames per run

No of frames as per tie line

No. of frames actually exposed

No. of Photos selected for scanning

1

40 E-W

31

11-41

5-24

1635

989

2

9 N-S

8

41-68

8-11

626

311

3

11 N-S

22

84

5-12

1121

313

4

15 E-W

8

21-32

7-16

473

365

5

15 E-W

8

29

8-13

516

357

6

1

0

4

4

4

7

5 E-W

2

13

81

38

4456

2377

8

Total

Table 2 GPS Reference Station for Airborne GPS

Sl. No. 1 2 3 4 5 6 7 8 9 10 11 12 13

Reference Station Hanimaadhoo Alifushi Rasdhoo Nilandhoo Kaashidhoo Male Kolhufushi Veymandoo Kadhdhoo Kaadehdhoo Gemanafushi Fuvamullah Gan (South)

Block 1 1 2 2 3 3 3 4 4 5 5 6 7

Table 3 GPS Reference & Target / Rover Stations

Sl .No. 1 2 3 4 5 6 7 8 9 10 11 12 S.No. 1 2 3 4 5

Block-1 Reference Station Hanimaadhoo Alifushi

Block-2 Reference Station Rasdhoo Nilandhoo

6 7 8 S.No. 1 2 3 4 5 6 7 8

Target/ Rover Station Innafinolhu Kelaa Kanditheemu Makunudhoo Feevah Maafaru Kothafaaru Dharvandhoo Thulhaadhoo Goidhoo Kanifushi Maabinhuraa Target/ Rover Station Thoddoo Feridhoo Dhigurah Hukurudhoo Filitheyo Hulhudheli Kandinma Kudahuvadhoo

Block-3 Reference Station Kaashidhoo Male Kolhufushi

Target/ Rover Station Gaafaru Reethirah Dhiffushi Guraidhoo Kunaavashi Fotheyobodufushi Raimandhoo Thuvaru

S.No. 1 2 3 4 5 6 S.No. 1 2 3 4 S.No. 1 S.No. 1 2 3

Block-4 Reference Station Veymandoo Kadhdhoo

Block-5 Reference Station Kaadehdhoo Gemanafushi

Block-6 Reference Station Fuvamullah Block-7 Reference Station Gan (South)

Target/ Rover Station Buruni Vilufushi Kandoodhoo Ishdoo Maavah Hithadhoo Target/ Rover Station Kolamaafushi Vilingili Fares Gan Target/ Rover Station Fuvamullah Target/ Rover Station Hithadhoo Hulhumeedhoo Gan

Table 4 Results of Aerotriangulation of entire Maldives shown as blockwise Block No.

Scale of Photography

No. of images

No. of GCPs

Pixel size(µm)

σ0 (µm)

Empirical accuracy (RMS) of GCPs µX (cm) µY (cm) µZ (cm)

1

1: 40,000

824

13

21

10

29.2

15.4

18.3

2

1: 40,000

262

6

21

10

21.8

12.0

14.4

3

1: 40,000

458

9

21

10

25.2

8.5

3.5

4

1: 40,000

238

7

21

10

12.8

11.4

25.9

5

1: 40,000

260

4

21

10

5.6

1.6

4.3

7

1: 40,000

32

3

21

10

2.6

2.0

1.0

Table 5 List of maps for entire Maldives in 1: 25 000 scale Block

Sl. Number

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

1-2 3-6 7-9 10-12 13-15 16 17-19 20-23 24-27 28-31 32-35 36 37-40 41-42 44-47 48-51 52 53-54 55-58 59-61 62-64 65-67 68-71 72-74 75-78 79 80 84 85-86 1 2-3 4-6 7-10 11-12 13-14 15 16-19 20-23 24-27 28-31 32-35 36-37 38 39 40-41

Map Sheet Number 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N

01 02 02 02 02 02 03 03 03 03 04 09 10 10 10 10 10 10 11 11 11 11 11 11 11 11 11 11 12 04 04 04 04 05 05 05 05 05 05 05 06 06 12 13 13

P K M N O P M N O P M D A B C D G H A B C D E F G J K L A K L O P I J K M N O P M N C C D

SE, SW NE, SW,SW,SE, NE, NW,SE NE, SW, SE NE, NW, SE NE NE, SW,SE NE, NW, SW, SE NE, NW, SW, SE NE, NW, SW, SE NE, NW, SW, SE SW NE, NW, SW, SE NE, NW NE, NW, SW, SE NE, NW, SW, SE SW NW, SW NE, NW, SW, SE NE, NW, SW NW, SW. SE NE, NW, SW NE, NW, SW, SE NE,NW,SE NE, NW, SW, SE SW NE, NW, SW, SE NW NW,SW SE NE,SE NE,SW,SE NE, NW, SW, SE NE,SE NE,SE NE NE,NW,SW,SE NE, NW, SW, SE

NE, NW, SW, SE NE,NW, SE

NE, NW, SW, SE NE,NW SW SW NW,SW

Total

86

2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 5 6 7

42-43 44 1-2 3-5 6-9 10-13 14 15-17 18 22-23 24-27 28-31 32-33 35-38 39 40 43-46 47-49 50 51-54 55 56-58 1 2-3 4 5-6 7-10 11-12 13 14-15 16-17 18-19 20 22-24 26-27 1 2 3-4 5-8 9-12 13-14 15-18 19-22 23-26 27 28 29-30 1 1-4 Grand Total

43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43N 43M 43M

14 14 12 12 12 12 12 12 12 12 13 13 13 13 13 13 13 13 13 14 14 14 06 06 06 14 14 14 14 14 14 14 15 15 15 08 08 16 16 16 16 16 16 16 16 16 16 09 09

A B E F G H I J K L E F G H I J K L O E F I N O P B C D F G H L A E I N O A B C D E F G H J K F C

NW,SW NW NE,SE NE,SW,SE NE, NW,SW,SE NE, NW,SW,SE SW NW, SW, SE NE, NW,SW,SE NW, SW NE, NW,SW,SE NE, NW,SW,SE NE, NW, SE NE, NW, SW, SE NW NW, SW, SE NE, NW,SW,SE NW, SW, SE NW NE, NW,SW,SE NE NE, NW, SW SE NE,SE NE SW,SE NE, NW,SW,SE NE,NW SW NW, SW SW,SE NW,SW NE,SE NE, NW,SW,SE NW, SW SE NE NE, SE NE, NW,SW,SE NE, NW,SW,SE NE, NW NE, NW,SW,SE NE, NW,SW,SE NE, NW,SW,SE NW SW NW, SW NE NE,NW,SW, SE

44

58

27

30 1 4 250

Table 6 Name of the selected islands in 1: 1 000 scale S. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Island Name NILANDHOO FUNADHOO MAAMIGILLI NAIFARU VILLIGILLI GURAIDHOO HUVARAFUSHI GADHDHOO MALE K_FUNADHOO HULHULE KEDHIKULHUDHOO MULI HITHADHOO HANIMAADHOO FOAMMULAH GAN (SOUTH)

Table 7 Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping Sl. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Layer list BOUNDARY_ISLAND BUILDING_DUCT BUILDING_GROUP BUILDING_INDUSTRIAL BUILDING_SHED BUILDING_SINGLE BUILDING_UNDERCONSTRUCTION CANOPY CULTIVATION FOUNTAIN_AREA LAGOON MARSHY_LAND PALMYRA_GROUP PARK PLANTATION PLATFORM PLAYGROUND POND ROAD_ISLAND STADIUM SWIMMING_POOL TANK

Feature POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON

Remarks

TREE_COVER

ELEVATED_SURFACE

WATER_TANK(MANMADE)

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72

TANK_CIRCULAR TANK_DRY TANK_OIL TANK_SQUARE WATER_TANK_SINTEX WELL_AREA BOAT_CHANNEL BUILDING_ELEVATION BUILDING_RIDGE DEEP_WATER_LINE DRAIN EMBANKMENT FENCE FOOTBRIDGE HEDGE HELEPAD JETTY PARKING_AREA PIPELINE PROTECTED_WALL ROAD_BLACKTOP ROAD_BLACKTOP_CENTER ROAD_BRIDGE ROAD_CARTTRACK ROAD_CARTTRACK_CENTER ROAD_CULVERT ROAD_DIVIDER ROAD_FOOTPATH ROAD_METAL ROAD_METAL_CENTER ROAD_UNMETAL ROAD_UNMETAL_CENTER ROCKAWASH RUNWAY RUNWAY_CENTER SAND STEPS STREAM UNSPECIFIED WALL BUILDING_HEIGHT FLAGPOLE FOUNTAIN IDGAH MANHOLE MOSQUE NAVIGATIONAL_LIGHT OHT PALMYRA POWERPOLE

POLYGON POLYGON POLYGON POLYGON POLYGON POLYGON LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE LINE POINT POINT POINT POINT POINT POINT POINT POINT POINT POINT

CHANGE ELEVATED LINES

73 74 75 76 77 78 79 80 81 82 * *

STATUE TOWER TREE_COCONUT TREE_OTHER WELL TXT_COCONUT TXT_CULTIVATION TXT_SAND TXT_FEATURES TXT_NAME BOUNDARY_ISLAND_AREA BUILDING_GROUP_ELEVATION

POINT POINT POINT POINT POINT TEXT TEXT TEXT TEXT TEXT POLYGON POLYGON

Table 8 List of hardware and software established at Male, Maldives SL. NO 1 2 3 4 5 6 7 8 9 10 11

DESCRIPTION ERDAS IMAGINE PROCESSING ARC INFO BASE 9.0 AUTO DESK MAP 2004 LEICA PHOTOGRAMMETRY SOFTWARE(LPS) LTO 2 Tape Data Cartridge 24 PORT 10/100/1000T GIGABIT AUTO SENSE ETHEMET SNMP MANAGEABLE SWITCH STEREO VIEWING EQUIPMENT WTRELESS LIQUID CRYSTAL GLASSES, IR EMITTER FOR EACH WORK STATION SERVER SYSTEM FOR REMOTE SENSING AND DIGITAL MAP DATABASE STORAGE AND DATA SERVING WORKSTATION FOR REMOTE SENSING, GIS AND DIGITAL PHOTOGRAMMETRY OPERATIONS LARGE FORMAT INKJET COLOUR NETWORK PLOTTER HANDHELD GPS RECEIVERS

List of figures Fig. 1

Methodology for mapping at 1:25 000 scale using 1:40 000 scale aerial Photographs

Fig. 2

Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

Fig. 3

Seven Geographical Blocks for planning, managing and execution of the project

Fig. 4

NRSA’s SKA B-200 aircraft

Fig. 5

GPS Survey Pre Target

Fig. 6

Simultaneous observation of GPS reference / Pre-target Control point

Fig. 7

GPS Control Survey Deployment Plan

Fig. 8

Pre-target Control point imaged on aerial photograph

Fig. 9

Numbering schema for 1: 250 000 scale

Fig. 10

Numbering schema for 1: 50 000 scale

Fig. 11

Numbering schema for 1: 25 000 scale schema

Fig. 12

Aerial photography & Mapping of Maldives - timeline

Fig. 1 Methodology for mapping at 1: 25 000 scale using 1: 40 000 scale aerial Photographs RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-III DATA

FLIGHT PLANNING

AERIAL

PHOTOGRA

GPS SURVEY 

PHOTOPROCES SING

REFERENCE STATIONS FOR AIRBORNE GPS

SCANNING OF DIAPOSITI VES

GPS DATA PROCESSIN G 

AIRBORNE

AEROTRIANGUL ATION & BLOCK ADJUSTME ORTHOPHOTO DEM 2D MAPPING FIELD DATA

GIS GEODATAB

HARD COPY MAPS

Fig. 2 Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-IV DATA

FLIGHT PLANNING

AERIAL PHOTOGRAPHY

GPS SURVEY

PHOTOPROCESSING

REFERENCE STATIONS FOR AIRBORNE GPS GCPs - POST POINTED

SCANNING OF DIAPOSITIVES

GPS DATA PROCESSING AIRBORNE GPS GCPs

AEROTRIANGULATION & BLOCK ADJUSTMENT

3D MAPPING & CONTOURS FIELD DATA

GIS GEODATABASE

HARD COPY MAPS

Fig. 3 : Seven Geographical Blocks for planning, managing and execution of the project

Fig. 4. NRSA’s SKA B-200 aircraft

Fig. 5 GPS Survey Pre Target

Fig. 6 Simultaneous observation of GPS reference / Pre-target Control point

Fig. 7 GPS Control Survey Deployment Plan

Fig. 8

Pre-target Control point imaged on aerial photograph

Fig. 9 Numbering schema for 1: 250 000 scale

8N 7N 6N 5N 4N 3N 2N 1N 0 1S 2S 3S 4S 5S

Sheet Numbering for 1:250 000 scale 43N01 43N09 43N17 43N25 43N33 43N41 43N02 43N10 43N18 43N26 43N34 43N42 43N03 43N11 43N19 43N27 43N35 43N43 43N04 43N12 43N20 43N28 43N36 43N44 43N05 43N13 43N21 43N29 43N37 43N45 43N06 43N14 43N22 43N30 43N38 43N46 43N07 43N15 43N23 43N31 43N39 43N47 43N08 43N16 43N24 43N32 43N40 43N48 43M01 43M09 43M17 43M25 43M33 43M41 43M02 43M10 43M18 43M26 43M34 43M42 43M03 43M11 43M19 43M27 43M35 43M43 43M04 43M12 43M20 43M28 43M36 43M44 43M05 43M13 43M21 43M29 43M37 43M45 43M06 43M14 43M22 43M30 43M38 43M46

6S 7S 8S 72

43M07 43M15 43M23 43M31 43M39 43M47 43M08 43M16 43M24 43M32 43M40 43M48 73

74

75

76

77

78

Fig. 10

Numbering schema for 1: 50 000 scale Sheet numbering for 1:50 000 scale 0

15'

30'

45'

1deg

1deg 43N01A

43N01E

43N01I

43N01M

43N01B

43N01F

43N01J

43N01N

43N01C

43N01G

43N01K

43N01O

43N01D

43N01H

43N01L

43N01P

45’'

30’'

15’'

0

Sheets North of Equator

0

15'

30'

45'

0 43M01A

43M01E

43M01I

43M01M

43M01B

43M01F

43M01J

43M01N

43M01C

43M01G 43M01K

43M01O

43M01D

43M01H

43M01P

15'

30'

45'

1deg

43M01L

Sheets South of Equator

1deg

Fig. 11

Numbering schema for 1: 25 000 scale schema

Sheet numbering for 1:25 000 scale 0' 15'0”'

7'30"

15’0”

43N01A NW

43N01A NE

43N01A SW

43N01A SE

7'30"

0'

Sheets North of Equator

0' 0’'

7'30"

15’0”

43M01A NW

43M01A NE

43M01A SW

43M01A SE

7'30"

15'0”

Sheets South of Equator

Fig. 12

Aerial photography & Mapping of Maldives - timeline