Proceedings Article | 8 September 1998
KEYWORDS: LIDAR, Global Positioning System, Airborne laser technology, Ranging, Laser systems engineering, Kinematics, Data modeling, Associative arrays, Pulsed laser operation, Laser scanners
During October 1996, the University of Florida, the Florida Department of Environmental Protection, the Florida Department of Transportation and the United States Geological Survey-Center for Coastal Geology and Regional Marine Studies jointly conducted a demonstration/test project of airborne laser swath mapping. Project Laser Swath-mapping Evaluation and Resurvey, included mapping of more than three hundred kilometers of beaches, stretching from Mexico Beach, just east of Panama City, Florida, to the western tip of Perdido Key, Alabama. The observations collected along the beaches included returns from the water surface at a number of inlets and from near short portions of the Gulf. The typical flying altitude during the tests was 350 meters above the surface, with an airspeed of 75 meters per second. The laser swatch mapping system operated at 5000 pulses per second, and scanned in a saw tooth pattern with a scan angle of plus and minus 15 degrees and a scan rate of 25 Hz. More than 50 million data points were collected in about three hours of operations, spread over three days. Proprietary computer software was used by the vendor to combine aircraft orientation (roll, pitch and yaw) values from an inertial navigation unit in the laser scanning unit, the angular orientation of the scanner mirror, and the range data to compute vectors from the aircraft to the reflecting surface. These vectors were added to the location of the aircraft, determined by phase difference kinematic Global Positioning System observations to compute the coordinates of the reflecting surface at each measurement epoch, expressed in UTM Northings and Eastings and ellipsoid heights. Commercial software was then used to create a variety of products, including 3D shaded relief `snapshots,' contour maps, false colored maps, cross sections and profiles. Repeat coverage was used to estimate the short term repeatability of the measurements and comparisons with cross sections from classical surveying methods were used to estimate the accuracy of the airborne laser swath mapping results.
