The Global Magazine of Leica Geosystems
Dear Readers, New technologies are changing working styles and methods for almost everyone who captures, processes, or passes data on to others, or those who further process or visualize data themselves. Our everyday tasks and the whole job profile of our industry have changed over recent decades. The last 10 years, especially, have seen expansion into new business areas. One of the technologies that has helped grow our industry is laser scanning, which allows users to capture millions of points – whether from the ground or from the air – in the shortest possible time. Laser scanning has hugely expanded the range of possible applications of traditional surveying, while also creating entirely new ones. Some extraordinary projects have already been completed with the new Leica ScanStation C10, such as the scanning of the Mount Rushmore National Memorial in the USA, featured on the front cover of this Reporter. Scott Macleod of Loy Surveys, who took delivery of one of the first ScanStation C10s in Great Britain, has written an exciting article on his first experiences with the instrument. Another new system, the Leica Viva Series, which we introduced at the last Intergeo, is playing the leading role in Swiss mobile phone operator Swisscom’s major infrastructure project, while models from the proven Leica GPS1200+ and TPS1200+ series are in use on the Russian bridge “project of the century” over the Bosporus. Now if we’ve piqued your curiosity, I look forward to your visit at our booth at Intergeo in Cologne.
03 Scanning on Washington’s Shoulder 06 Accreditation Creates Confidence 08 Speeding Up on Channel Project 09 Embracing Point Clouds 12 Russian Marvel 14 Virtual 3D Urban Design from Laser Scan Data 17 Big Ship, Tight Space 20 Utility Mapping with GNSS 22 CORS-Qatar: Updating Maps in Real-Time 24 Reacting to Climate Change 26 Modeling Istanbul: World’s Largest Scanning Project 29 Controlling Vertical Towers
Imprint Reporter: Customer Magazine of Leica Geosystems Published by: Leica Geosystems AG, CH-9435 Heerbrugg Editorial Office: Leica Geosystems AG, 9435 Heerbrugg, Switzerland, Phone +41 71 727 34 08, email@example.com Contents responsible: Alessandra Doëll (Director Communications) Editor: Agnes Zeiner, Konrad Saal Publication details: The Reporter is published in English, German, French, and Spanish, twice a year. Reprints and translations, including excerpts, are subject to the editor’s prior permission in writing.
Juergen Dold CEO Leica Geosystems
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© Leica Geosystems AG, Heerbrugg (Switzerland), September 2010. Printed in Switzerland Cover: CyArk
by Elizabeth Lee
3D laser scanning has already changed the fields of surveying, engineering, construction, and forensics. Now, 3D laser scanning is changing the fields of education, cultural tourism, and cultural heritage preservation and management. With help and support from Scotland and Leica Geosystems, the non-profit organization CyArk carried out the first comprehensive documentation survey of the Mt. Rushmore National Memorial.
Scanning on Washington’s Shoulder In May 2010, teams from CyArk and the Scottish Center for Digital Documentation and Visualisation (CDDV), with additional support from Leica Geosystems, deployed an array of Leica Geosystems laser scanners to digitally capture the famous Mt. Rushmore National Memorial. The memorial is a spectacular sculpture carved high into the granite face of Mount Rushmore in South Dakota (USA). It features four 18 m sculptures of the heads of former US presidents George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln, or as many surveyors know them, “three surveyors and some other guy (Roosevelt).”
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The memorial park site covers more than 5 km² and is 1,745 m above sea level. The data capture is the first phase of a five-year project between CyArk and the U.S. National Park Service (NPS) to provide both engineering-grade data for tasks such as rock-block monitoring, analysis, and site resource management, as well as a base data set to create virtual tourism and educational materials for public outreach and data dissemination. The project deployed up to three teams, operating five scanners at once, in various locations throughout the park and on the mountain. Complete coverage of the mountain sculpture was a necessity for the engineering and interpretive needs of the park; therefore it was critical that all surfaces be scanned at a high level of accuracy and resolution. Four Leica Geosystems scanner models were used: Leica ScanStation 2, Leica HDS6000, Leica HDS6100, and the new Leica ScanStation C10. Each scanner model was strategically deployed within the site to utilize its unique strengths; for example the ScanStation 2
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with its long-range capabilities was used along the base of the mountain. The speed and dense data capture abilities of the HDS6000 and HDS6100 were used to capture all the details in the canyon behind the sculpture and throughout the park grounds. Because of its blend of range and speed the ScanStation C10 was used as the workhorse atop the mountain for wide-view scans of the sculpture. The new compact design of the ScanStation C10 and its on-board controls were essential for using the scanner in precarious positions on the mountain. In one setup location, the NPS ropes team and scan team lead, Douglas Pritchard of CDDV, rappelled from the top of the monument down to George Washington’s shoulder with the scanner. With the scanner secured on the president’s shoulder and the scan settings selected, Pritchard and the ropes team then rappelled off the side of the shoulder to avoid obstructing the scan. Scans captured from these positions were critical to the success of the project. To ensure accuracy and complete coverage of the mountain, a data command center was set up on
The CyArk 500 and the Scottish 10 The non-profit organization CyArk was created to apply the advantages of 3D laser scanning or HighDefinition Surveying™ (HDS™) to the field of digital heritage preservation. Rather than transporting engineers to a digital plant, CyArk virtually transports students and web travelers inside Native American ruins at Mesa Verde National Park (USA) or to the top of the Leaning Tower of Pisa in Italy. Instead of capturing a crime scene for analysis, CyArk works to capture cultural heritage sites around the world to create a shareable, 3D digital record of humanity’s tangible history. CyArk was created shortly after the Taliban’s dramatic destruction of the Bamiyan Buddhas in Afghanistan. Often credited as the Father of Laser Scanning, Ben Kacyra knew the power of laser scanning to capture the built environment. Envisioning the creation of a cyber archive for humanity’s cultural wonders of
site and all team members were equipped with twoway radio systems. CyArk’s Justin Barton used Leica’s Cyclone software to do daily registrations of the data. This allowed the scan-team members on the mountain or on the visitor’s trail to radio the command center for up-to-date information on the scans and instant feedback on proposed scanner setup locations.
the world, Kacyra (who also founded Cyra Technologies – now the laser scanning business unit of Leica Geosystems), founded CyArk in 2003. To date, CyArk has utilized HDS technologies to capture, process, archive, and disseminate digital data for over 30 heritage sites around the world. This progress became the catalyst for launching the “CyArk 500 Challenge”, a challenge to digitally preserve 500 important heritage sites. Upon hearing about CyArk 500, the Scottish Minister of Culture, Michael Russell, was impelled to get involved. Already using HDS technology within Scotland and eager to contribute to CyArk’s global mission, the visionary Scottish Minister made the generous commitment of the “Scottish 10”, the contribution of 10 projects to the CyArk 500. These projects consist of the five UNESCO World Heritage Sites within Scotland and five international projects.
The project was a tremendous success, resulting in the first comprehensive survey documentation of Mt. Rushmore. The capture of this American icon complete, CyArk is now at work creating the engineering and educational deliverables to supplement the laser scan data in the CyArk archive. There, a digital 3D Mt. Rushmore will sit alongside world treasures from around the globe as the CyArk team takes on future challenges to bring state-of-the-art survey and documentation techniques to other heritage sites for the benefit of future generations.
About the Author: Elizabeth Lee is Director of Projects and Development at CyArk. http://archive.cyark.org/
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Accreditation Creates Confidence by Sabine Reischmann
Leica Geosystems is one of few surveying instrument manufacturers in the world that is allowed to issue calibration certificates as a nationally accredited body. This expertise means increased transparency and better comparability. Accreditation and certification creates confidence in the mind of the customer. And to take this a step further: Leica Geosystems customers also gains from the confidence that their clients place in them. René Scherrer and Wolfgang Hardegen, the current and future managers of the accredited calibration laboratories for Leica Geosystems in Heerbrugg, compare calibration certificates with the fuel pump gauge at filling stations: “The customer must be able to trust that the gauge shows the actual quantity of fuel being pumped. The customer can be sure that what we promise is delivered.” A calibration certificate can be traced back to national standards and the measurement uncertainties of the measured values are fully documented. For the customer, this means that he can be certain the actual parameters and specifications of his Leica Geosystems product correspond with those quoted in the product literature.
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Several factors are critical to attaining the status of an accredited body. Hardegen identifies the first as quality management: “Our quality management system, which is certified in accordance with ISO 9001, forms the basis for accreditation.” The expertise of our staff is crucial: “All employees who work in the calibration laboratory at Leica Geosystems are trained accordingly.” Further prerequisites include an appropriate technical and organizational infrastructure. Technical infrastructure includes the premises; facilities and procedures; and consists of the measurement baseline as well as laboratories for distance, angle, frequency, and level measurements. A further accreditation is being sought to augment these five laboratories with a test laboratory for laser classification.
Baseline The baseline is not a typical laboratory, as it is situated on the west bank of the Rhine river at Kriessern, a village near Heerbrugg. “The bank of the Rhine here is straight for a length of three kilometers with no obstructions to the line of sight – something seldom encountered in the densely populated Rhine valley among high Alpine peaks,” explains Hardegen. Leica Geosystems can check the standard deviation of distance measurements over lengths of 500 m,
1,000 m, 2,000 m, or 3,000 m. The accurate determination of atmospheric parameters, such as temperature, pressure, and humidity is essential to obtain precise results.
Calibration Laboratory for Distance The calibration laboratory for distance, dubbed the “railway line” by staff because of its length and design, is used to determine deviations from linearity over distances of 60 m and 120 m. The results from this test determine the deviation of the highly accurate interferometer distance compared to the measured distance.
Calibration Laboratory for Angles The calibration laboratory for angles is used to determine the standard deviation of horizontal and vertical angle measurements. Leica Geosystems developed a very complex, highly accurate theodolite testing machine (TPM), the only one in the world, to carry out this task. This machine checks the horizontal circle and zenith angles of the instrument completely automatically.
Calibration Laboratory for Frequency In the calibration laboratory for frequency the accuracy of electronic distance meters (EDM) is checked in a climatized cabinet that can be set at any temperature between - 20° C and + 50° C. Analysis of the frequencies determines the scale error of the EDM.
Calibration Laboratory for Levels In the calibration laboratory for levels compensator setting accuracies or horizontal optical line of sight of levels are determined. The demand for certificates is continuously rising for various reasons. Wolfgang Hardegen cites the increased competitive capability of customers in tendering for public works contracts as a strong driver. Large private companies also often ask for certificates or customers themselves like to be accredited according to ISO 9001. But the main value added for the customer is still increased transparency, confirmation of confidence in the instrument by Leica Geosystems, and the improved comparability with respect to other products.
Accreditation of Calibration Laboratory In 1997, the Swiss Accreditation Service (SAS), which forms part of the State Secretariat for Economic Affairs (SECO), confirmed Leica Geosystems in Heerbrugg as an accredited body with a calibration laboratory for distances and angles. Through multilateral agreements with international organizations such as EA (European cooperation for Accreditation) and ILAC (International Laboratory Accreditation Cooperation), these certificates are internationally recognized in well over 100 countries. “Calibration certificates are legal documents. Their falsification is considered forgery and perpetrators would be appropriately punished,” stresses Wolfgang Hardegen, as he highlights the credibility of the certificates. Calibration laboratories have to be accredited by the Swiss Accreditation Service (SAS) every five years. Annual audits are carried out in accordance with ISO/IEC17025 by the supervisory authorities between accreditations. Official information about Leica Geosystems’ accredited laboratories (SCS 079) can be found on the SECO website (see below; search for 079 under Search “Accredited bodies”). The document lists the tests the laboratory can carry out, as well as measurement accuracies and uncertainties. http://www.seco.admin.ch/sas/
About the author: Sabine Reischmann is Marketing Communications Executive at Leica Geosystems in Heerburgg/Switzerland.
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Speeding Up on Channel Project by Daniel C. Brown
A 3D excavator guidance system is helping earthmoving subcontractor Ebert Construction beat the schedule by 15 percent on a 9-million USD channel repair project for the U.S. Army Corps of Engineers in Topeka, Kansas. Ebert Construction Co., Wamego, Kansas, is using Leica Geosystems machine control systems on its excavators to help reshape 2.5 miles (4 km) of the channel at Soldier Creek, which is contained by two parallel levees spaced 300 feet (91.5 m) apart. In 2005 a major flood eroded the creek banks. This project will repair the damage, helping to prevent further flooding upstream of the reconstructed area. Ebert has engaged a fleet of earthmoving equipment to remove 350,000 cubic yards (270,000 m³) of earth from the side slopes and take them to waste areas behind the levee. Some 170,000 cubic yards (130,000 m³) are being moved from cuts to fills on the slopes. Two hydraulic excavators, each fitted with a Leica PowerDigger 3D machine control system, are being used to shape the side slopes. Each slope is designed
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with an upper and a lower bank, both on a 3:1 slope and separated by a gentler 10:1 slope. Jim Ebert, project manager for the contractor, says the Leica PowerDigger 3D systems improve the excavators' efficiency because no grade checking is needed. He further states that the systems save Ebert 40,000 USD a year by eliminating the grade checker. The PowerDiggers' screen shows the operators the cuts and fills on a continuous basis. “Plus”, says Ebert, “we can work underwater without having a grade checker climb into the water.” “The Leica Geosystems GPS system takes the guesswork out of grading for the operators,” says Trent Ebert, project superintendent. “And there's no more calling us to say the stakes got run over by a dozer. There's no downtime. Nobody has to watch the operators; they can dig, back up, find the next place to cut and keep on going.” Completion is scheduled for February 2011, but the contractors hope to achieve substantial completion before winter. About the author: Daniel C. Brown is the owner of TechniComm, a communications business based in Des Plaines, Illinois/ USA.
Embracing Point Clouds by Scott Macleod
Loy Surveys had been aware for a number of years that laser scanning was going to be the next big thing in surveying and would eventually become a mainstream technology. They knew they would have to master it in order to stay at the leading edge of surveying. The only question was, when? Senior Surveyor Scott Macleod on how they met the challenge. With the technology changing at a rapid pace and becoming increasingly more affordable, it was a case of finding the right balance. Fortunately we had the
opportunity to purchase the first commercially available Leica ScanStation C10. This is a bit of kit that appealed to us and our style of workflow in a big way. Not only was it a significant step ahead of previous scanners, it provided us with an excellent entry point into scanning. Being both faster and lighter it was ahead of the game and looked as though it would be the pacesetter for the next few years. The fact that everything came in a single manageable package and did not need cables, external batteries, and laptops to operate it, meant it fitted perfectly into our flexible working system. Once in possession of the Leica ScanStation C10 we were able to put it straight to work.
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Monitoring Cooling Towers With a job in the pipeline we were able to get an early delivery of the ScanStation C10. The job was to carry out a survey of three cooling towers at the Grangemouth Oil refinery on Scotland’s Firth of Forth. The ScanStation C10 was delivered to us on the first morning of the job by Steven Ramsey from Leica Geosystems. Steven was there for more than just delivery. He had been involved in the testing and development phase of the ScanStation C10 and, as we were going to be the first company to use it on commercial work, he joined us so that he could demonstrate its capabilities and observe the scanner in a commercial environment. The purpose of the job was to survey the cooling towers with a view to identifying any movement and changes of shape or deformations in the tower structures. Previous surveys had involved observing points at set heights along a number of vertical lines around the tower. Although these surveys had not been carried out by Loy Surveys, we believed that this method of setting out and surveying fixed points
around the tower could take two or possibly more days per tower. By using the ScanStation we were able to survey the three towers over the course of two days, with a survey time for each individual tower of approximately 2 ½ hours. Not only was this a massive saving in site time, we were also able to record infinitely more data on the cooling towers. Each tower was scanned by placing the ScanStation C10 over known control points. A total of five overlapping positions were used on each tower and they were scanned at a 30 mm grid. Importing and registering the individual scans proved straightforward with the Leica Cyclone 7 software and in less than an hour’s office time we had a 3D model of the tower.
Dounreay Castle One of our most recent jobs has been to carry out a 3D scan of Dounreay Castle on Scotland’s north coast. The castle, a scheduled monument (protected national monument), is unique in this area of Scotland, as it has an L-shaped footprint that is more commonly found in the Scottish Lowlands. This makes it an important part of the history and heritage of the area.
“... future comparisons between 3D scanned models will not be so cumbersome ...” As the castle is in a poor state of repair, Historic Scotland are keen to see something done in order to maintain and preserve the castle. It is currently owned by the Dounreay nuclear facility and is trapped by the coast on one side and the nuclear facility on all others. The nuclear plant is currently being decommissioned and the security and monitoring controls in place during this process mean that it is not viable or affordable to carry out a physical restoration of the castle at present. With this in mind we were approached by Dounreay Site Restoration Ltd and asked to carry out a 3D scan of the castle as a means of preservation by record. Only an exterior survey of the castle was possible. Its dilapidated condition meant that for health and
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safety reasons we were not allowed within 10 m of the structure. The ability to scan the castle was ideal as it meant we could record it quickly and efficiently at relatively low cost (compared to physical restoration), and at the same time remain at a safe distance from the structure. The survey itself was carried out over two days with a total of eleven overlapping scan positions. At a different site, without the security protocols, we could potentially have completed the survey in a day. The castle was surveyed with an overlapping grid of 8 – 10 mm or less so that we had enough information to see and record the individual stones within the coursework. The end product for the client was the full point cloud data, which they could present to Historic Scotland as a record of the castle in its current state for future use and reference. We also produced 2D elevation drawings.
Convincing Clients Looking at the long term, we see scanning as becoming the norm in the survey world, and are aiming to reach an ideal position where we will carry out the scanning, register the data, and then pass the raw point cloud straight to the client so that they can use the data as they see best. This has huge benefits for both us and our clients. For us it means less office time and accordingly more survey time, which boosts
“… we have made the right move at the right time …” our productivity. For our clients, they are able to get full 3D surveys in a fraction of the time and at an affordable price. At present however, only a small number of our clients are in a position to accept and deal with full point cloud data, but this is something we are keen to rectify. With the purchase of the Leica ScanStation C10, Loy Surveys has taken a major step into the world of 3D scanning. In doing so we are expanding our capabilities as a survey company and keeping ourselves at the leading edge in a competitive industry. Having put the ScanStation C10 to use, it is easy for us to see the huge advantages to be gained through highly detailed rapid 3D surveys, produced in record time. Although new to scanning and still with much to learn, we have no doubt that we have made the right move at the right time. About the author: Scott Macleod originally worked as an archaeologist, but soon developed an interest in land and building surveying and joined Loy Surveys four years ago.
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Russian Marvel by Pavel Antonov
Once finished, the “Bridge to Russky Island” will connect the city of Vladivostok with Russky Island and it is no exaggeration to say it is “the project of the century”. The bridge will be the largest in Russia and one of the longest worldwide, with a total span length of 3,100 m. The 1.2 billion USD project, also proudly called “The Russian Bridge”, is scheduled to be finished by the opening of the Asia-Pacific Economical Cooperation summit to be held in 2012 in Vladivostok. Leica Geosystems equipment was chosen to execute the surveying work. In September 2008 the main contractor, USK MOST, started construction work for the “Bridge to Russky Island” across the so called “Eastern Bosporus”, connecting Russky Island to the city of Vladivostok. Before it even started, it had already gained the status of one of the most demanding building projects in history. Not only because of the sheer dimensions of the bridge – the unique central span of 1,104 m will be the longest in the world, the 320 m tall bridge pylons will be the highest – but also because the works are to be carried out on a tight schedule while extreme winds, sea currents, and seismic activity are a great challenge for the professionals involved.
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Due to very strict project requirements, all surveying tasks are being carried out with the highest possible accuracy: from construction design to post-construction control. This is why Leica Geosystems equipment was chosen to help complete this demanding job.
Surveying Tasks During Construction The first task for the contractor was to supply a precise and reliable control network. A geodetic network (complying with the requirements of the State Geodetic class II network) was created on Nazimova Peninsula and Russky Island. The contractor had to re-determine position and height coordinates of the network points every six months, but as this was nearly impossible to do with optical equipment, GNSS sensors were chosen for the task. A reference station mounted by Leica Geosystems’ Russian dealer and partner Navgeocom was already available in nearby Vladivostok, to deliver correction data for precise RTK measurements. Two more reference stations were mounted on Nazimova Peninsula and Russky Island, both equipped with Leica GPS 1200+ GNSS sensors. Before starting measurements in real time surveyors had to determine transformation parameters from WGS84 datum to the local coordinate system, so that RTK jobs could be used in the local coordinate sys-
Bridge to Russky Island Total bridge length: 1,885.5 m Bridge width: 29.5 m Number of driving lanes: 4 (two in each direction) Under clearance: 70 m Number of bridge towers: 2 Bridge tower height: 320.9 m Number of cable stays: 168 Longest/shortest cable stay: 578.08 m/181.32 m
The bridge piles will be driven 77 m below ground. On the island side 120 auger piles will be piled under each of the two 320 m high bridge towers. The bridge towers will be concreted using custom self-climbing forms in pours of 4.5 m. Due to the A-shape of the towers the use of standard forms is not feasible. An individual set of forms were constructed for each bridge tower. (Source: www.wikipedia.org)
USK MOST USK MOST was founded in 1991. A highly professional team, experienced in another “construction project of the century” – the long term construction of Baikal Amur Railway Project (BAM, 1975 - 1990) –
tem. Anton Shirokov, senior surveyor at USK MOST: “Every construction stage was thoroughly controlled by different geodetic methods; this is why we were able to fulfill all requirements of geodetic tasks. The difference between parameters obtained by TPS and GNSS measurements were no more than 3 – 4 mm, which was within the required tolerances. GNSS surveying is really important when there is no way to perform TPS measurements.” Due to the strict requirements, surveyors had to draw from their wealth of professional know-how and experience in every construction phase. For example: to obtain the most precise positioning for bridge pylon parts, engineers used “conductors” (or “towers”). Connected within different levels of concrete, these elements helped strengthen the whole construction. There came a time when it became too difficult to use total stations for this task, so Leica Geosystems GNSS receivers were used to position these “towers” in their proper place in real-time. GNSS-technology helped reduce work time from approximately 1.5 hours per “tower” to 15 min. The time benefit is obvious.
Leica Geosystems Was the Best Choice “We only started to work with Leica Geosytems equipment in February 2010,” says Anton Shirokov. “In this
runs the company. Nowadays “USK MOST” is a holding consisting of 15 different companies. Its activities cover repair and construction works for bridges, pipelines, tunnels, etc.
short time, it has completely fulfilled and surpassed our expectations! Firstly, Leica Geosystems sensors have a comprehensive, friendly user interface – this means less loss of work time. Secondly, the equipment performed magnificently in our severe environment with snow, wind, and low temperatures, all of which never interrupted our sessions.” USK MOST professionals have also remarked on some of the exceptional functions of Leica Geosystems equipment, such as the excellent performance of the Leica TPS1200+ laser pointer by night. With this, measurements could be performed even 450 m from the total station. After the pylon height exceeds 100 m, triangulation will not be possible any more, so professionals working with a combined TPS/GNSS system. “Leica Geosystems equipment is modular and scalable,” says Anton Shirokov, “you can work with a total station or combine it with a GNSS system, to set up a Leica SmartStation or a Leica SmartPole. This way, you obtain baseline measurements to perform tasks even when the visibility is poor.” About the author: Pavel Antonov is head of the technical department of Navgeocom, Leica Geosystems’ authorized dealer in Russia.
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Virtual 3D Urban Design from Laser Scan Data by Konrad Saal
The Inselhalle in Lindau, Germany, a conference center on an island in Lake Constance, was to be refurbished and extended to meet modern requirements. Since only incomplete records of the original building existed, project organizers decided to capture the existing features of this old conference hall and its surroundings using laser scanning. The acquired data is now available to architectural consultants for their designs and for virtual “tours”. Consulting engineers Zimmermann & Meixner Z&M 3D Welt GmbH, from nearby Amtzell, won the contract for the building inventory documentation and 3D visualization. Their task was to capture the details of the whole hall (interior and exterior) and the adjacent features including the bank of the lake in the vicinity of the conference hall.
Survey of Existing Features Using 3D Laser Scanning Surveying technician Viola Leibold and graduate engineer Benjamin Sattes arrived on the island with
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a Leica ScanStation 2 to produce as-built recordings of the original buildings and surrounding features. This versatile 3D laser scanner captures up to 50,000 points per second and has a range of up to 300 m. “Laser scanning provides surveyors with a way to overcome the hurdle of capturing the features of existing objects at an adequate level of detail precisely and cost-effectively,” explains Benjamin Sattes. “The 3D laser scanner is linked to a laptop and controlled using the Leica Cyclone software package, which consists of several different modules. This arrangement allows the user to define the required scan window and point density and store the captured point data. Targets are set up and scanned at the same time as the object to permit subsequent geo-referencing, the linking of all captured point clouds into a single, consistent system. We captured an area of about 73,000 m² from 38 stations in five days. The interior, for which we needed about 21 stations over three days, involved a total area of 5,000 m²,” says Viola Leibold. The Lindau fire brigade even made a turntable ladder available to capture the roofscape.
To edit the point clouds Leica Geosystems offers modules that can interface with a number of engineering CAD programs, allowing users to work in their familiar software environment. The expanded and partially automated functions in Leica CloudWorx for AutoCAD allowed Benjamin Sattes to generate a 3D model of the whole object from the point clouds. “Any section or view can be generated from the model once complete.” Two cross-sections; layout plans of the basement, ground, and first floors; as well as four views were generated for the Inselhalle. The 25 architectural consultancies selected for the design competition used the model as the basis for their designs. With a maximum deviation of one centimeter from the actual dimensions of the building, the data is considered equivalent to surveys of the highest quality.
3D Visualization and Virtual Tours “The particular aim of the exercise was to capture the features of the Inselhalle at such a level of detail and precision that the architects would have access to a robust and comprehensive survey of the existing building and would not have to produce one themselves,” explains Benjamin Sattes. “At the same time,
we were able to use Leica Geosystems’ free Internetbased visualization software TruView to allow people to take a virtual tour of the Inselhalle.” Leica TruView can be used to analyze and take measurements within large point clouds in a CAD or other 3D technology environment, even for users without 3D laser scanning experience. The point clouds are presented as photorealistic images. Architects can move around in a virtual world inside the point cloud, measure distances, highlight details, make annotations, and save the results. The project participants can also use the processed data to communicate effectively over the Internet. Using 2D layouts and a 3D model of the existing building, and with TruView as a substitute for a site visit with the additional feature of being able to take measurements, each architect has the optimum basis for expressing his ideas and designs.
Linking Designs to the Real World Thanks to the visualization concept developed inhouse by Z&M 3D Welt, the architects, civil engineers, and landscape planners can see how their proposals and plans would look in the context of the
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Z&M 3D Welt is able to visualize the real environment from the raw laser scanning results. The captured point clouds visualize the existing objects and do not have to undergo further processing into 3D models with the customary loss of detail and accuracy.
The Sustainability of Using 3D Models
Leica TruView: Moving around in a virtual world inside the point cloud to take distance measurements.
real situation. The design results can be delivered to Z&M 3D Welt as 3D models or 2D views. The company will then develop 3D models from the 2D drawings or directly import the 3D models created in the customer's own choice of software module. The data is visualized in three-dimensional space with a new road layout, open space design, landscape architecture, and the existing real buildings and features. The process is particularly interesting because of its cost-effectiveness compared to previous methods:
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Users are often faced with the question of how best to make data available for future use with minimum cost and effort. The data obtained from laser scanning can be accessed immediately to provide measurements from the 3D model and pass them on to the judging committee. The competitors particularly appreciate the ease of operation â€“ it is so easy that no experience is needed to move about freely within the model. The future designs and animations for the â€œInselhalle Lindauâ€? project can be found at: www.zm-3dwelt.de/ inselhalle. About the Author: Konrad Saal is a surveying engineer and Marketing Communications Manager with Leica Geosystems in Heerbrugg, Switzerland.
Big Ship, Tight Space by Brad Longstreet and Dave Murtha
With a clearance of about 226 feet (69 m) between Mean Lower Low Water (MLLW) and the span underside of the San Francisco Bay Bridge, there’s usually plenty of room for the world’s biggest ships to pass through on their way to the Port of Oakland. But when one of those ships is loaded with three of the world’s tallest container cranes, maybe there’s not enough room … or maybe there is. The job of deciding fell to Dave Murtha, the Port’s chief surveyor. The cranes in question are “Super-PostPanamax” and they’re monsters – PostPanamax ships are too big for the Panama Canal, and as more are built, ports around the world are installing cranes that can accommodate them. In this case, the cranes being delivered are wide enough to reach across vessels carrying up to 22 Sea-Land style cargo containers side by side. Of more concern to Murtha was their height: 253 feet (77 m). When loaded on a ship big enough to carry them, this would easily exceed the Bay Bridge’s clearance.
The crane’s designers knew this, and planned to cut and fold the cranes shortly before passage was attempted. But this still left plenty of uncertainty. To be sure he was making the right call, Murtha would have to precisely equate tidal elevation values and NAVD 88 (North American Vertical Datum of 1988), determine the absolute Bay Bridge clearance, and verify the total height of ship and cranes. And just to complicate matters, he would have to do it all in real-time; the San Francisco Bar Pilots who oversee large vessel operations in the Bay wanted verification of sufficient clearance as the cranes approached the Bay Bridge. The Bay Bridge, incidentally, is known to have several feet less clearance than the Golden Gate Bridge, so Murtha’s work would automatically confirm that the cranes could pass under the Golden Gate. Murtha had an idea that made use of his extensive experience with leading edge survey techniques: “Since RTK GPS methods are now being used to measure elevation profiles of airport runways, it didn’t seem like a big stretch to adapt RTK methods to verify load clearance. I told people in my organiza-
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tion that I could measure the height of the cranes as they approached the bridge. Eventually my claim got passed on to the San Francisco Bar Pilots, and they were very interested in having me provide that information.” Airport runway profiles can be postprocessed and re-measured if necessary … but given the inertia of giant cargo vessels, there would be no second chances to re-measure as the cranes approached the bridge.
Laying the Groundwork Providing real-time information for this project required painstaking preparation for several reasons. For example, Murtha knew he needed a backup plan. “Redundancy was a very important part of the survey plan,” he says, “Two different RTK rovers would be used at the top of the load of cranes, one using cellular modem communication equipment, and the other using a spread-spectrum radio modem.” The cellular modem could access a Leica GRX1200 Pro permanently installed at the Port’s headquarters. This receiver is part of RTKMAX, a subscription real-time network operated by Haselbach Surveying Instruments (Leica Geosystems’ authorized dealer for Northern California). But for reliable radio link RTK, he would need a base station with line-of-sight from both the Golden Gate and Bay Bridges. “The levee on the west side of Treasure Island was the perfect location,” says Murtha. Work was already underway to verify the Port’s reference station and relate it to tide station values.
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Murtha says: “I included the Port’s reference station in a GPS control survey which I am submitting to the National Geodetic Survey (NGS). The control survey was mostly conducted in June 2009 using Leica ATX1230GG antennas. Additional vectors focusing on height differences were measured in August 2009. This control survey consists of more than 100 vectors and also includes several miles of leveling conducted in June 2009 with a Leica DNA03 digital level and a calibrated pair of Wild GPCL3 Invar rods. Four different tidal bench marks were part of this control survey.” To supplement the work for the crane height survey, Murtha planned a static control survey with two objectives: establish the needed base station location and elevation on Treasure Island, and relate local tide datums to NAVD 88. He included six stations in the final network. With control firmly established; tide related to available benchmarks and NAVD 88; and the Treasure Island station set, Murtha could move on to additional tasks in this challenging project: verifying Bay Bridge clearance and crane height above the deck of the transport vessel.
Tricky Measurements on the High Seas In 2000, when a shipment of Post-Panamax container cranes was delivered to the Port of Oakland at the Navy’s former Fleet Industrial Supply Center (FISCO) in Oakland, Port personnel measured the Bay Bridge’s mid-span clearance by trigonometric leveling methods. This time, Murtha used RTK to establish a spot elevation on the upper deck of the bridge,
then used a Leica TCRP 1201 total station to transfer elevation from that point to a magnetically mounted prism target that was visible from the upper deck and from the base of the nearest suspension tower pier. Then, in what must have been a fun day in the field, Murtha took a boat to the pier and set up his total station. Two CalTrans (California Department of Transportation) employees, certified to climb on the bridge, used safety harnesses and belaying equipment to set another prism directly on the bridge’s bottom chord. Murtha was able to confirm a clearance of 226 feet (69m) above MLLW. The three cranes, standing their full 253 feet (77m) tall, arrived at Drake’s Bay, north of San Francisco, on March 12, 2010, loaded on the Zhen Hua 15, a tanker with a specially modified low deck. While anchored at Drake’s Bay, the crew of the Zhen Hua 15 spent three days folding over the crane apexes. Two days later, Murtha traveled by boat to the vessel to verify the final crane height, and to set GPS antenna mounts at the top of the middle crane. It turned out to be another exciting day in the field: “The crew of the Zhen Hua hoisted our equipment up to the boom level of the crane, which is about 180 feet (55 m) above the deck of the vessel. Since the apex had been folded over more than 70 degrees, the stairs to reach the boom of the cranes were much more difficult to climb – think of a jungle gym 200 feet in the air slowly rocking back and forth with the waves. Once we got to the top we set ourselves to the task of setting up the GPS antenna mounts. I had modified two old tripods by removing the metal points and replacing them with three inch (7.6 cm) diameter disk magnets attached to the tripod legs by metal hinges. Since tripods are excellent for setting up over non-level surfaces, I figured these modified tripods would be the best way to setup the antenna mounts.” With antenna mounts in place, Murtha and his crew returned to the deck to take total station measurements. Since the rolling of the deck ruled out the use of the vertical compensator – “I could see the bull’s eye bubble moving back and forth” – Murtha turned it off and took a series of measurements intended to define the deck plane and crane height above deck. Back in the office, he “performed a classic sevenparameter, three-dimensional coordinate transformation,” which confirmed what the crew’s engineers
had told him – the cranes had been lowered even more than planned, and should clear the bridge with about 10 feet (3 m) to spare.
The Big Day The transit was set for March 16th. The Port of Oakland employees once again climbed to the boom level, donned safety harnesses, and climbed to the top of the center crane. Even with all the checking and rechecking, it was still a tense moment; “We got there just a few moments before the Zhen Hua reached the Golden Gate Bridge,” says Murtha, “and we were happy to see it pass under with what looked like 15 feet (4.5 m) of clearance.” Murtha put his equipment into stakeout mode and started gathering data: “We hadn’t yet reached Alcatraz, so we were still more than three miles away from the Bay Bridge, and I was able to tell the pilot that we had 9 feet (2.7 m) of clearance. I called him again when we were between Alcatraz and Treasure Island, and he called me once more when we were much closer to the Bay Bridge to confirm the clearance values. Shortly after that I realized I could see the bottom of the bridge, so I called him on the radio one more time and said, ‘I can see the bottom of the bridge. We’re definitely going to clear it!’” About the authors: Brad Longstreet is a freelance writer who specializes in construction and surveying. Dave Murtha is the Chief Surveyor for the Port of Oakland.
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Utility Mapping with GNSS by Thorsten Schnichels
Reliable digital data acquisition, robustness, and ease of use – these were the requirements stipulated by Swisscom AG when it set out to acquire new GNSS instruments to determine the positions of telecommunication infrastructure in the company's country-wide fixed-line network. After a detailed evaluation the Swiss telecommunications company decided in favor of Leica Viva GNSS. “Determining and recording the position of items in our telecom network has been a long-standing daily chore for us – in particular since cables were first buried underground,” explains Andreas Häsler, Technical Project Manager at Swisscom. The conventional
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methods being used were time-consuming and error prone. Swisscom was therefore seeking a more efficient and reliable method of data acquisition that would reduce these recurring daily costs to a minimum.
Measuring System Requirements The first requirement was for the measuring system to provide reliable digital data acquisition to allow data transfer to be extensively automated. Furthermore, the system had to be robust, easy to transport, and able to be used by staff who had no detailed knowledge of surveying. The new satellitesupported surveying system Leica Viva GNSS fulfilled all these requirements – in addition to the GNSS and communications technology, the client was also impressed by the systems’ newly designed, easy to use software, Leica SmartWorx Viva.
GNSS (Global Navigation Satellite System) receives GPS satellite data as well as signals from other systems (e.g. the Russian GLONASS satellites). The higher signal density provides more reliable reception, which is necessary since Swisscom has to carry out most of its surveys in urban areas. Corrections are transmitted via mobile phone to the swipos reference service to achieve an accuracy of 1 â€“ 2 cm.
Example of an imported DXF infrastructure map on the Viva Controller. Measured points and items are shown immediately.
Comprehensive Training and Support Concept At the same time, Swisscom and Leica Geosystems worked together to devise a comprehensive training and support concept: ten people identified as SuperUsers, would, after intensive training, pass their knowledge on to the 150+ Swisscom field engineers who have access to the large pool of Leica GNSS Viva instruments. The instruments are managed and the firmware kept up to date through the myWorld@ Leica Geosystems Internet portal. The same system offers Super-Users a continuous overview of all support and service cases. Besides capturing the positions of existing cables, the Leica Viva GNSS Rovers will also be used to set out new telecom cables.
Instruments and Software Leica Viva GNSS (GS15, CS10) used by approx. 150 engineers Leica SmartWorx Viva software
Objective Higher productivity with better quality at lower cost
Benefits Simple to operate Rapid, accurate, and safe capture of objects Reliable and robust system
About the author: Thorsten Schnichels is sales and support engineer at Leica Geosystems AG, Glattbrugg/Switzerland.
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CORS-Qatar: Updating Maps in Real-Time by Konrad Saal
In the past few years the State of Qatar, a peninsula on the Arabian Gulf, has experienced extensive infrastructure development. More than twenty years ago the results of a user needs assessment carried out by the government clearly indicated an enormous need for a fully integrated nationwide GIS. The government then established the Centre for GIS (CGIS) as a department of the Ministry of Municipality & Urban Planning. It is based in the capital Doha and became the official mapping agency of the State of Qatar. Since the end of October 2009, many public and private survey and mapping communities have been benefiting from a nationwide Continuously Operating Reference Station (CORS) network. The CORS network was set up with receivers, antennas, high-precision tilt sensors, and GNSS Spider software from Leica Geosystems. Delivering highly accurate data and comprehensive customer services, the CORS network now plays a major role in all geodetic and topographic surveys to update Qatarâ€™s
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maps, as well as in integrating collected GIS data into the common nationwide GIS database. CGIS setup the CORS network to help achieve country-wide, homogenous horizontal and vertical accuracy and to ensure the availability of RTK corrections for all survey and mapping communities in Qatar. Many agencies can now log on to the CORS network to carry out their tasks without needing to setup single base stations. The new CORS-Qatar network consists of nine reference stations and helps many organizations using RTK and GIS rovers receive differential corrections for their day-to-day activities. All reference stations are homogenously distributed throughout the country and were established at Al Shamal, Al Thakhira, Al Jumailiya, Dukhan, Al Kharanah, Abu Samra, Mesaieed and Sawda Natheel, and finally, at the Qatar University in Doha. Each of the nine reference stations is equipped with future proof Leica GRX1200+ GNSS receivers and highly accurate Leica AR25 choke ring antennas. Due to the high temperatures in Qatar, the receivers are installed in air-conditioned indoor and outdoor cabinets. The control center of the CORS-Qatar network is located
at the Urban Planning sector building in Doha. CGIS decided in favor of Leica Geosystems equipment because of its high quality, outstanding customer service, ease of use, and product durability. In the meantime, the system has already passed durability tests in the Middle Eastern summer temperatures.
Reliable GNSS Data and Comprehensive Service The physical stability of the antennas fixed on rigid masts is monitored to ensure the CORS network delivers reliable and precise data. They are monitored by Leica Nivel220 dual-axis high-precision tilt sensors that deliver an accuracy of 3 mm @ 1,000 m. The data is continuously streamed to check stability. Tilt measurements at the Al Thakhira site for testing purposes had proven that the position of the Leica AR25 is very stable at 0.45 mm. Additionally, the stability of the climatization inside the cabinets is monitored by meteo sensors measuring temperature and humidity. The CORS-Qatar network is managed by CGIS. With Leica GNSS Spider, CGIS provides correction data for precise measurements for RTK surveys through TCP/IP, network processing, raw data streaming status, and satellite tracking for its customers 24/7. Leica Spider Web is used for the convenient distribution of GNSS data sets for public or internal access via standard web browsers. The software allows keeping track of data, downloads, users, and costs while providing additional services such as automatic coordinate computation and a constant overview of file availability and data quality. Registered clients can simply upload their GNSS raw data. SpiderWeb then uses one or more nearest reference stations to calculate the coordinates of their data sets. Leica GNSS Spider with SpiderNet software then processes the raw data to issue correction information to the users in the field. The network and the services of CGIS bring numerous benefits to users of RTK for land surveys. The system operates without downtime and since its establishment has routinely been used by land surveyors and GIS professionals to position themselves with high accuracy anywhere within Qatar. Leica Geosystems Spider Business Center makes it easy to manage and track customers’ access to the RTK network services.
Quick and Accurate Update of Maps After the installation of the CORS network, agencies began mapping Qatar’s main roads in real-time.
Many public and private survey and mapping communities now have access to CORS-Qatar.
Points were automatically recorded at regular intervals of 5 m. No office processing of the data was required and the data could be quickly integrated into the common CGIS database via GISnet highspeed network. Qatar is the first country to implement a comprehensive nationwide GIS and is internationally recognized as having one of the finest GIS implementations in the world. The CORS network is now constantly in use for GIS and GNSS surveys to keep Qatar’s maps up-to-date. The network is also used for hydrographic surveys, offshore and ocean navigation. In the years to come, as Qatar’s infrastructure develops further, many of the organizations working with GNSS will benefit from the homogenous CORS network that provides consistent, high accuracy 24/7. All installed Leica Geosystems receivers and antennas are ready for future signals. More information about the Centre for GIS in the State of Qatar at: www.gisqatar.org.qa
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Reacting to Climate Change by Konrad Saal
‘Sweden facing climate change – threats and opportunities’ is the title of final report SOU2007:60 presented by the ‘Swedish Commission on Climate and Vulnerability’ in 2007. Appointed by the Swedish government in 2005, the commission’s task is to assess the impact of global climate change on the country. Over the last decades Sweden has suffered from significantly rising numbers of floods, landslides, and erosion. The persistent and increasing risk will affect buildings, roads, and many other infrastructure facilities. The Swedish government has granted a considerable amount of money to protect Sweden’s society, infrastructure, industry, and agriculture. One of the preventive measures is a new digital elevation model delivering highly accurate elevation data of Sweden. As the Swedish mapping, cadastral, and land registration authority, Lantmäteriet is responsible for the national co-ordination of the production, cooperation, and development of geo-data. In 2009,
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Lantmäteriet received a special grant from the government to start the new terrain elevation database using airborne laser scanning technology. “The existing national Digital Elevation Model (DEM) database covering Sweden is unsuitable for most of today’s tasks. It was initially created only for in-house production of orthophotos. Over time, it has become obvious that a better DEM database is of great importance for many required activities in the coming years,” states Gunnar Lysell, Business Developer at Lantmäteriet. Furthermore, the existing model provides a height accuracy of only ± 2 m and has a 50 m grid spacing.
Highly Accurate LiDAR Data Acquisition In summer 2009, Blom Sweden AB, a subsidiary of Norway based Blom ASA, started the five-year project. They were chosen to provide LiDAR data to Lantmäteriet, but before the project could start the Swedish mapping authority needed to verify the LiDAR data from test flights. Among the equipment chosen for data capture was a Leica ALS60 airborne laser scanner. It delivered outstanding results that fully met Lantmäteriet's expectations.
Visualizing Historical Shorelines A first processing of the data has disclosed patterns of historical shorelines after hiding the vegetation. “These shorelines are remains of the raised sea level after the last ice period some 10,000 years ago. Ice melting caused an uplift of the land, up to almost 300 m in some parts of Sweden,” explains Lysell. “Before the new, accurate elevation data, this pattern could only be found through field research, but now we can see it easily by viewing the elevation model on our computer screens.” The old elevation model with 50 m grid and a height accuracy of approximately ± 2 m could not resolve the patterns. Even today, the land is still rising at a rate of approximately 1 cm per year in the central part of Sweden.
BLOM Group is a leading international company specializing in the collection and processing of highquality geographic information using airborne sensors and the development of software applications and services. Andreas Holter, Head of Resources at BLOM, says: “LiDAR has become an efficient technology to create digital terrain models of large areas. The Leica ALS60 meets Lantmäteriet’s specifications, delivering a height accuracy on hard and well defined surfaces of 20 cm or better.” BLOM uses Leica AeroPlan60 to set up the ALS60, and the Leica FPES software for cost efficient and detailed flight planning and evaluation. The software computed a total flight length of 550,000 km in approximately 12,500 lines for the entire project. According to the flight plans created in FPES, the sensor is automatically activated for data acquisition by the Leica FCMS Flight & Sensor Control Management System. Up to 70,000 “shots” are captured per second. The collected data is geo-referenced via GNSS base stations which provide ground control points. This data is post-processed through different software, such as Leica IPAS Pro, NovAtel’s GrafNav/GrafNet, Leica ALS Post Processor, Terrasolid's TerraScan/TerraMatch, and BLOM’s own TEPP software, and finally converted into ground coordinates including latitude, longitude, elevation, and intensity values. Andreas Holter confirms, “We are very satisfied with the support from Leica Geosystems in the integration of Leica ALS Post Processor with our own software TEPP. This has sped up the processing workflow. The accuracy of the final processed data is very good, mainly because of the high accuracy
Inertial Measurement Unit (IMU). This, combined with good flight and processing procedures, including strip adjustment and ground truth verification, has produced very good results.“
Great Benefits for Many Organizations Lantmäteriet uses the geo-referenced point cloud data to calculate the new digital elevation model. “The benefits of the project appear to be many. We have noticed a great interest from potential users of both the DEM database and of laser data,” says Gunnar Lysell. “The data can be used for almost anything. We expect all Swedish Municipalities will use it for their planning of new infrastructure and for flood protection planning.” The data can also be imported into GIS software suites and advanced software packages to simulate floods for future infrastructure planning. “The forestry industry will definitely use the laser data for investigations on the wood yield of Swedish forests,” continues Lysell, “and even Swedish orienteering clubs will use it for production of orienteering maps.” For public authorities, municipal and governmental, the elevation data will be available as part of the European wide “Inspire” project. “When the new data is available to end users, we will publish references on our website to various applications where the data is being used,” concludes Gunnar Lysell. Of course, Lantmäteriet will use the data to update their orthophoto production and to put height values on cartographic features mapped in 2D.
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Modeling Istanbul: World’s Largest Scanning Project by Geoff Jacobs
With a population of over 12 million, Istanbul is the world’s 5th largest city. Its rolling terrain, rich architecture, and Bosporus Strait views also make it one of the most magnificent. In 2003, UNESCO designated large portions of the historic Istanbul peninsula as protected areas. All further development of these areas was stopped until a detailed and highly accurate as-built 3D city model could be created for use by the city planning commission. It was urgent to complete the 3D city model as quickly as possible to lift the moratorium on development. The need to create the model quickly and with high accuracy triggered the largest terrestrial scanning project ever undertaken: 48,000 buildings (11,000 of which had great historic importance), 1,500 hectares, 5.5 million m² of facade, and 400 km of city streets. Included in this project was the creation of highly accurate and detailed 3D models of many cultural landmarks, including the famous Topkapi Palace and Hagia Sophia mosque.
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The project was conducted by IMP – BİMTAŞ, the Istanbul Metropolitan Municipality’s Directory of the Protection of Historical Environment. Over a period of 18 months it involved approximately 120 field & office staff and five Leica Geosystems HDS scanners, including one in mobile mode.
Requirements Requirements of 1/500 and 1/200 scale for the first and second degree protection areas were critical. This translated into a requirement of 2 cm point density for scanning facades. Landmarks, such as the Süleymaniye mosque, required an even higher scan density of 5 – 10 mm. All scan data had to be georeferenced for use in a city-wide GIS. Of course, the other critical requirement was the 18-month schedule. After the data was collected, three types of deliverables were required. One was a 3D wire frame model of all of the external building facades and walls. For cultural landmarks, fully textured 3D models were required. For key city landmarks a third type of deliverable was needed: a physical, solid 3D model made
from computer models by a 3D printing device. These “exact replica” models are used on official occasions by city personnel.
scan speeds > 125,000 points/sec. Scans were registered and tied to control using scan targets placed on tripods, facades, or other convenient locations. Control points were surveyed with total stations.
Field Methodology To accomplish the data collection of the building facades in the city’s narrow and crowded streets, BIMTAS used four short-range, Leica HDS phasebased scanners (HDS4500) on tripods. Each featured
Scanning the Suleymaniye Mosque required a longrange, high-accuracy Leica Geosystems laser scanner.
For cultural landmarks, BİMTAŞ turned to Leica Geosystems’ versatile, high accuracy time-of-flight scanner (HDS3000). Although not as fast as phasebased scanners, this scanner was needed to achieve high-accuracy (6 mm), high-density (5 – 10 mm spacing) scan data at long ranges. The Süleymaniye mosque, for example, features a 76 m minaret and 55 m dome. As the project progressed, it became apparent that even with four static phase-based scanners, the schedule for the mammoth undertaking was in jeopardy. To remedy this, BİMTAŞ secured the system integration services of VisiMind from Sweden to develop a mobile scanning system for one of the phase-based scanners. BİMTAŞ was able to scan while driving up to 5 km/h in the crowded city streets and still achieve the required accuracy and 2 cm point density.
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Happy Clients and More Customers
After the scan data was cleaned, registered, and geo-referenced (in Leica Cyclone Register software), office staff worked within a custom 3D CAD environment to create the final 3D wire frame CAD deliverables, including detailed stonework. These CAD models were, in turn, combined with high resolution photographs in 3D Studio Max to create final, textured models of stunning visual quality, all with 2 – 3 cm overall accuracy.
Working with a highly accurate 3D city model, Istanbul city planners were extremely pleased. Prior to this, they made important planning and zoning decisions based solely on 2D drawings and photos. With an accurate 3D model, they can better visualize proposed projects, overlaying them in 3D against the current city model. In particular, they can assess the impact of proposals on views across the city’s many beautiful areas. Another big plus is their ability to accurately account for the rolling terrain and its impact on views affected by new proposals. The Istanbul 3D City Modeling project was so successful that BİMTAŞ has received similar requests from other cities for their scanning and modeling services and executed additional projects with impressive and valuable results. About the author: Geoff Jacobs is Senior Vice President, Strategic Marketing, for Leica Geosystems’ HDS business.
All laser scan data were accurately geo-referenced.
3D point clouds of facades along Suleymaniye Kirazli Mescit street.
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Controlling Vertical Towers by Joël van Cranenbroeck
There has been considerable interest in the construction of super high-rise and iconic buildings recently. From a surveying perspective, these towers present many challenges. The Burj Khalifa in Dubai and the Al Hamra tower in Kuwait, for example, have risen into territory previously uncharted: methods and processes normally used to control tall buildings have needed a rethink. Leica Geosystems’ Core Wall Control Survey System (CWCS) delivers precise and reliable coordinates on demand that are not influenced by building movements. In addition to being very tall, high-rise buildings are often quite slender and during construction there is usually a lot of movement of the building at upper levels due to wind loads, crane loads, construction sequence, and other factors. It is essential that a straight “element” be constructed that, theoretically, moves around its design center point due to varying loads and, if all conditions were neutral, would stand exactly vertical. This ideal situation is rarely achieved due to differential raft settlement, differential concrete shortening, and construction tolerances. Structural movement creates several problems for correct set-out of control: at a particular instant in
time the surveyor needs to know exactly how much the building is offset from its design position and at the same time he must know the precise position at the instrument location. Construction vibrations in the building and building movement further complicate this situation, making it very difficult, if not impossible, to keep an instrument leveled up. Leica Geosystems has developed and tested a surveying system, the Core Wall Control Survey System (CWCS), using networked GNSS (GPS and GLONASS) sensors combined with high precision inclination sensors and total stations to deliver precise and reliable coordinates on demand that are referenced to the design frame, where the construction was designed and projected, and that are not influenced by building movements. These coordinates are used to control the position of the climbing formwork systems located at the top of any vertical structure, such as a tall building under construction, as well as to monitor the dynamics and behavior of the structure implemented.
Active Control Points and Inclination Sensors As on most construction sites, surveyors typically work around steel structures and obstructions and beneath or beside materials being lowered by crane. The working areas are congested with materials,
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equipment, and people, and of course working at height requires a special regard for safety. Under these conditions surveying becomes difficult. In time, surveying becomes very much a steering of the vertical alignment of every single wall element by making discrete corrections to the position of each, but with strict limitations placed on the amount of correction per rise. This needs to be done while the structure continues to move as usual. The optimum method for placing survey control for tall buildings needs much consideration. The use of conventional methods such as optical plumbing of control through slab penetrations is very limited for such structures. Core walls are constructed in a sequence of several concrete pours. After each pour, three to four GNSS antennas combined with a GNSS permanent reference station and a total station are set up. The total station observes the geometry of the GNSS antennas by measuring angles and distances to the 360° collocated reflectors (Active Control Points). This information and the GNSS data are either post-processed at the survey office or calculated in real-time on site. The resulting coordinates are transferred to the total station to update its coordinates and orientation.
Precise dual-axis inclination sensors are installed at ground level and at about every given number level above. The information from the inclination sensors is logged at the survey office and the exact amount in Δx and Δy that the building is offset from its vertical position is applied as corrections to the coordinates of the Active Control Points. The total station then observes the control points (nails set in the top of the concrete) to derive the corrections to be applied to the formwork structure. These coordinates are in relation to a continuous line of the building as defined by the control lines and therefore when the points are used to set the formwork for the next pour, the construction progresses as a straight element regardless of building movement.
From WGS to Gravity Vertical All the results from GNSS surveying refer to an ellipsoidal normal as reference for the Z component (WGS84). Therefore a transformation is carried out to transform the results obtained by GNSS to the same local coordinate reference frame as the primary survey control network. If this transformation is limited to a single point, the difference between the gravity vertical (that could be visualized by a plumb line) and the ellipsoid normal (deflection of the vertical) will introduce a bias that will impact the vertical alignment of the construction. The transformation needed to get GNSS to provide coordinates and orientation for the total station is derived by using the coordinates of the reference frame and the coordinates obtained for the same marks with GNSS. To summarize, GNSS receivers, automatic total stations, and precise inclinometers must all refer to the same reference frame, where the gravity vertical is the most sensitive component as the building’s main axis reference.
Benefit The real advantage is that the surveyor is able to continue to set control – even when the building has moved “off centre” – confident that he will construct a straight concrete structure. With the networked dual-axis precise inclination sensors he also obtains precise information about building movement.
Burj Khalifa in Dubai (828 m)
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The analysis isolates factors such as wind load, crane loads, and raft slab deformation and also relates movement to the construction sequence. This information is of great benefit in explaining to the client
what is actually happening to the structure. If there is a trend in any one direction it can be identified and an RFI (request for information) submitted for a correction based on reliable data obtained over a long period of time. Another advantage is that the surveyor is able to get precise positions at the top of the formwork without the need of sighting external control marks, which become increasingly difficult to observe as the building rises. The control surveys are completed in a shorter time, improving productivity, and the instruments do not need to be leveled during the survey, which is an important consideration when the building is moving or there are vibrations.
A Tribute to Chief Surveyors and Structural Engineers
similar system and a professional surveyor that would be able to drive it. Soang Hoon from South Korea was willing to accept the challenge and became Chief Surveyor for the contractor. Even though the system was similar to the one delivered for the Burj Khalifa, he made necessary adaptations and we learnt how tall buildings are different even if, from a surveying point of view, they have the same specifications. A year after the installation in Kuwait, we were asked to provide a CWCS system for the Landmark tower in Abu Dhabi. This tower was again slightly different and the contractor had great interest in having the system run in real-time mode. Mohammed Haider, structural engineer for the contractor, oversees the system and has been an outstanding supporter.
Doug Hayes, an Australian surveyor who worked on a number of large construction projects world-wide and was Chief Surveyor at Samsung Engineering & Construction, United Arab Emirates, immediately recognized the merit of Leica Geosystemsâ€™ Core Wall Survey Control System proposal and largely contributed to the success of its implementation during the construction of Burj Khalifa in Dubai.
In this article I tried to review the state of the art of an innovative surveying method to support the construction of outstanding vertical structures. The dedicated involvement of the surveyors and engineers in this process has contributed greatly to the sophistication of our system. In the near future we would not be surprised to receive requests for semi or fully automatic systems. After all, it is only the first step in a long journey.
A short time after the installation of the CWCS in Dubai we were contacted about the Al Hamra tower project in Kuwait. The contractor was requesting a
About the author: JoĂŤl van Cranenbroeck is Business Development Manager for Leica Geosystems, Heerbrugg, Switzerland
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www.leica-geosystems.com Head Office Leica Geosystems AG Heerbrugg, Switzerland Phone +41 71 727 31 31 Fax +41 71 727 46 74
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Poland Leica Geosystems Sp. z o.o. Warsaw Phone +48 22 260 50 00 Fax +48 22 260 50 10
United Kingdom Leica Geosystems Ltd. Milton Keynes Phone +44 1908 256 500 Fax +44 1908 256 509
China P.R. Leica Geosystems Trade Co. Ltd. Beijing Phone +86 10 8569 1818 Fax +86 10 8525 1836
Italy Leica Geosystems S.p.A. Cornegliano Laudense Phone + 39 0371 69731 Fax + 39 0371 697333
Portugal Leica Geosystems, Lda. Moscavide Phone +351 214 480 930 Fax +351 214 480 931
UAE Leica Geosystems c/o Hexagon Dubai Phone +971 4 299 5513 Fax +971 4 299 1966
Denmark Leica Geosystems A/S Herlev Phone +45 44 54 02 02 Fax +45 44 45 02 22
Japan Leica Geosystems K.K. Tokyo Phone +81 3 5940 3011 Fax +81 3 5940 3012
USA Singapore Leica Geosystems Techn. Pte. Ltd. Leica Geosystems Inc. Norcross Singapore Phone +1 770 326 9500 Phone +65 6511 6511 Fax +1 770 447 0710 Fax +65 6511 6500
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Leica Geosystems AG Heinrich-Wild-Strasse CH-9435 Heerbrugg Phone +41 71 727 31 31 Fax +41 71 727 46 74 www.leica-geosystems.com