HR: 0800h
AN: G51B-0433    [Abstracts]
TI: Survey-scale airborne lidar error analysis from parallel swath comparison
AU: * Borsa, A A
EM: aborsa@usgs.gov
AF: U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106, United States
AU: Bevis, M
EM: mbevis@osu.edu
AF: The Ohio State University, 275 Mendenhall Laboratory 125 South Oval Mall, Columbus, OH 43210, United States
AU: Hudnut, K W
EM: hudnut@usgs.gov
AF: U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106, United States
AB: The determination of robust system calibration parameters and reliable survey error statistics is still an area of active research in airborne laser altimetry. We show how these twin challenges are in part related to long-period GPS noise due to multipathing and tropospheric effects. Systematic differences in absolute GPS positioning over periods of tens of minutes to hours mean that a major component of airborne survey error is both time and space dependent and cannot be determined by local measurements alone. Furthermore, it is standard practice to compare intersecting swaths at one or two locations to determine calibration parameters for a given flight. Correlation between vertical translations and other geolocation biases means that calibration parameters determined without explicitly accounting for GPS elevation error might inadvertently correct a portion of this error and thus be incorrectly estimated. Angular errors would then be apparent in footprint geolocation at other points in the survey. We diagnose error in a recent airborne laser altimeter survey by comparing 5 parallel and partially overlapping swaths from a continuous flight over a section of the Southern San Andreas fault (from the 2005 "B4" Survey). Correlated elevation errors between swaths range over +/- 10 cm, which may explain the presence of linear "corduroy" patterns in DEMs created from point cloud data. Although this survey segment was calibrated to remove biases in aircraft attitude and laser scan angle, the pattern of the residual misfit throughout much of the flight (e.g. across-track "ramps" in elevation) suggests that the estimated calibration parameters are not optimally determined. We also show the effect of long-period GPS noise on the mean bias between swaths and report on an attempt to independently estimate and remove this error.
DE: 1294 Instruments and techniques
DE: 7250 Transform faults
SC: Geodesy [G]
MN: 2007 Fall Meeting