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Global Positioning System (GPS) has been used so extensively and widely in the Middle East that explaining it, and proving its usefulness and advantages, has become redundant. On the other hand, Laser Scanning Technology (LST) has been evolving and is fast becoming the method of choice for an increasing number of applications in the western world. Its serious introduction and integration in the business activities conducted in the Middle East is eminent. This article will highlight this issue briefly, as GeoTech is dedicated to providing its customers with the highest possible standards of technology.
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Internet Provides an environment that can be accessed “virtually” everywhere. Please see Figures 2 and 3 for samples.
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Figure 1: Registered point clouds (Hawarey and Falk, 2004)
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The tremendous growth in LST research and applications can be ascribed to several reasons, such as the provision of 3D point clouds with color intensity information that can represent any object with the internal precision of few millimeters. While this technology has already found its customers in the entertainment sector, such as some of Hollywood’s movies, it has also been implemented to capture the scene of the twin towers in New York City just after the 9/11 incidents. On another occasion, the whole city of Austin, Texas was scanned from an airplane using LST (Ouellette, 2002). Archeologists appreciate this technology because of the power it provides them. They can scan any object, dismantle it, then reconstruct it within a few millimeters of accuracy. The space industry has been implementing LST for some time. The construction industry has been using LST to measure deflections in steel columns (Hawarey and Falk, 2003 & 2004), and to simulate the installation of huge objects in an as-built environment (Hawarey and Falk, 2005). Figure 1 shows sample multiple point clouds registered onto each other with millimeter accuracy.
In a study that took place at Purdue University (Bethel, et al., 2003), LST was integrated with GPS to study the as-built status of a bridge near Indianapolis International Airport in the USA. Bridgeport bridge was scanned by LST to be represented by 2,756,495 points; as seen in Figure 2.
Figure 2: Bridge represented by ~ 2.75 million points (Bethel, et al., 2003)
Figure 3: Point clouds of LST correctly geo-positioned onto MXRoad data (Bethel, et al., 2003)
Then a GPS campaign was carried out to geo-reference these registered point clouds to another point cloud provided by the Indiana Department of Transportation (INDOT) in MXRoad format, which had been acquired by aerial LST, usually called LiDAR (Light Detecting And Ranging). Integrating both sets of LST data resulted in one single compiled data set as seen in Figure 3 with a maximum horizontal error of 3.8 cm and a maximum vertical error of 1.5 cm.
Going one step further, the mid part of the bridge was modeled as seen in Figure 4.
Figure 4: Mid-part of Bridgeport Bridge, as point clouds represent it and as modelled (Bethel, et al., 2003).
The modeling process enabled volume measurements, distance measurements, surface meshing or fitting, and even Digital Elevation Model (DEM) generation, as seen in Figure 5.
The ability to scan small and medium sized objects can be extended to large scale areas, such as scanning a whole city from the air, as shown in Ouellette (2002). This would enable us to efficiently build virtual cities in 3D digital medium. Also, it would enable us to acquire very strong representation of Digital Elevation Model in urban and rural areas.
Figure 5: Volume between mesh with DEM
contours and reference plane (Bethel, et al., 2003).
In conclusion, LST is a very promising technology, and it can be integrated with GPS smoothly, as described in this article, to produce magnificent results which enable engineers to carry out various analysis tasks that can assist them in design, maintenance or construction processes. Intuitively speaking, this indicates the ease and practicality of integrating LST with Geographic Information Systems (GIS), too.
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mhawarey@ags-group.com
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Dr. Mosab Hawarey got his B.S. in Construction Management from Middle East Technical University. He has an M.S. Degree in Geodesy from Middle East Technical University, and an M.S.C.E. in Geomatics Engineering from Purdue University. Upon completion of his first Ph.D. in Geodetic and Photogrammetric Engineering from Istanbul Technical University, he ceased his second Ph.D. studies at Purdue University. He has wide expertise in Turkey, USA, and Austria in GPS, Geodesy, VLBI, GIS, and Laser Scanning.
He has recently joined GeoTech’s team at Saudi Arabia.
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