From Bureau of Economic Geology, The University of Texas at Austin (
For more information, please contact the author.


Austin Geological Society, February 2001

Airborne LIDAR at The University of Texas

Rebecca C. Smyth, Roberto Gutierrez, James C. Gibeaut, Tiffany L. Hepner, and John R. Andrews1; Melba Crawford, Bob E. Schutz, Amy Neuenschwander, J. Trelogan, and Chris Weed2; W. Gutelius, and others3


The University of Texas at Austin has acquired an airborne LIDAR (Light Detection and Ranging) instrument for mapping the earth's surface. Our instrument is an ALTM 1225 (Airborne Laser Terrain Mapping System) manufactured by Optech Inc. of Toronto, Canada. The ALTM is mounted in a single-engine Cessna 206 modified for aerial photography. The ALTM instrument utilizes a pulsed laser operating at 25kHZ and scanning optics to measure the topography in a wide swath below the aircraft. Airborne LIDAR mapping requires the integration of three basic measurement sources: (1) laser ranges and associated scan angle information; (2) aircraft attitude information from an Inertial Measurement Unit (IMU); and (3) an absolute aircraft trajectory derived from a differential, geodetic Global Positioning System (GPS) network. By combining these measurement streams we obtain x, y, z data with an vertical precision of 10-15 centimeters and a horizontal spacing as close as 1 meter. In addition to precise elevation data, the Bureau's LIDAR system provides laser intensity imagery that is being evaluated as a new remote sensing data source.

Since 1997 the BEG has conducted LIDAR surveys for FEMA, NASA, the Texas General Land Office, and the USGS in coastal, forested, urban, and mixed-use areas for flood-hazard, landslide, and shoreline mapping. During the year 2000, the BEG mapped the entire Texas Gulf shoreline from Sabine Pass to Brownsville. Other survey areas include Lakewood, California, Austin, Texas, Bentsen-Rio Grande State Park, and fifteen municipalities in Honduras, C.A. The ALTM data from these surveys are typically used to generate high-resolution digital elevation models (DEM). Contour maps, three-dimensional images, and two-dimensional, topographic cross-sections are other products that can be derived from ALTM data.

1 Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713.

2 Center for Space Research, The University of Texas at Austin, 3925 West Braker Lane, Suite 200, Austin, Texas 78759.

3 Optech, Inc., Toronto, Canada.