A Kinematic Terrestrial LIDAR Scanning System

Craig Glennie

Abstract:	Terrapoint has developed a novel kinematic terrestrial based laser scanning system, called TITAN™ (Tactical Infrastructure and Terrain Acquisition Navigator) that can be deployed on a passenger vehicle or small watercraft. LIDAR (Light Detection And Ranging), digital imagery and digital video are collected from the survey platform while it is moving at speeds up to 100 km/h. The system is georeferenced using a high accuracy GPS/INS system. The laser scanner assembly in TITAN™ acquires 360 degrees of coverage in the LIDAR point cloud with a single vehicle pass. Commercially available airborne LIDAR systems have been deployed for more than a decade, and the technology has been widely accepted as a fast and efficient means of capturing topographic information. The accuracy of the final 3D LIDAR point cloud is directly affected by the accuracy of the underlying GPS/INS trajectory utilized to georeference the LIDAR measurements. For airborne systems, obtaining the highest accuracy is primarily accomplished by paying close attention to maintaining the integrity of the GPS solution. As airborne GPS for remote sensing is collected in a fairly benign environment (i.e. minimal signal shading, low dynamics, lack of loss of lock) a reliable GPS solution can normally be obtained by preplanning missions during good PDOP windows, maintaining benign flight characteristics (i.e. no steep banks of aircraft) keeping baseline length short, and not flying during periods of high ionospheric activity. In the kinematic terrestrial case, obtaining an accurate and reliable trajectory for the ground based platform is a much more difficult and challenging task than that of an airborne platform due primarily to increased multipath and frequent GPS signal outages caused by obstructions such as buildings, bridges, terrain and vegetation. Again, careful mission planning can mitigate some of these problems by traveling the optimum route, and by preplanning locations for zero velocity updates of the IMU. Given the dynamic and fast-changing environment w.r.t. GPS positioning, it is often a much more difficult challenge to ensure the reliability and integrity of the final post-processed terrestrial trajectory However, the simultaneous collection of LIDAR data from the vehicle platform provides an accurate 3D reference that can be utilized to check the reliability, accuracy and consistency of the GPS/INS derived vehicle trajectory. Repeated passes over the same area provide a tool to observe long term biases in the trajectory by analyzing the time differences in the LIDAR point clouds. Overlap between sensors in the TITAN™ LIDAR array can also be used to examine short-term changes in the GPS/INS trajectory, and have proved invaluable in locating and removing undetected GPS cycle slips. Some examples of this will be presented. Methods of utilizing the LIDAR data to validate and improve the GPS/INS trajectory will be discussed. Finally, overall absolute accuracy of survey results obtained with the kinematic terrestrial LIDAR system (when compared with dense DGPS ground control) will be presented and discussed.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1625 - 1630
Cite this article:	Glennie, Craig, "A Kinematic Terrestrial LIDAR Scanning System," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1625-1630.
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