HR: 08:00h
AN: G11B-01    [Abstracts]
TI: Defining and Verifying Research Grade Airborne Laser Swath Mapping (ALSM) Observations
AU: * Carter, W E
EM: bcarter@ce.ufl.edu
AU: Shrestha, R L
EM: rshre@ce.ufl.edu
AU: Slatton, C C
EM: cslat@ce.ufl.edu
AB: The first and primary goal of the National Science Foundation (NSF) supported Center for Airborne Laser Mapping (NCALM), operated jointly by the University of Florida and the University of California, Berkeley, is to make "research grade" ALSM data widely available at affordable cost to the national scientific community. Cost aside, researchers need to know what NCALM considers research grade data and how the quality of the data is verified, to be able to determine the likelihood that the data they receive will meet their project specific requirements. Given the current state of the technology it is reasonable to expect a well planned and executed survey to produce surface elevations with uncertainties less than 10 centimeters and horizontal uncertainties of a few decimeters. Various components of the total error are generally associated with the aircraft trajectory, aircraft orientation, or laser vectors. Aircraft trajectory error is dependent largely on the Global Positioning System (GPS) observations, aircraft orientation on Inertial Measurement Unit (IMU) observations, and laser vectors on the scanning and ranging instrumentation. In addition to the issue of the precision or accuracy of the coordinates of the surface points, consideration must also be given to the point-to-point spacing and voids in the coverage. The major sources of error produce distinct artifacts in the data set. For example, aircraft trajectory errors tend to change slowly as the satellite constellation geometry varies, producing slopes within swaths and offsets between swaths. Roll, pitch and yaw biases in the IMU observations tend to persist through whole flights, and created distinctive artifacts in the swath overlap areas. Errors in the zero-point and scale of the laser scanner cause the edges of swaths to turn up or down. Range walk errors cause offsets between bright and dark surfaces, causing paint stripes to float above the dark surfaces of roads. The three keys to producing research grade ALSM observations are calibration, calibration, calibration. In this paper we discuss our general calibrations procedures, give examples of project specific calibration procedures, and discuss the use of ground truth data to verify the accuracy of ALSM surface coordinates.
DE: 1214 Geopotential theory and determination
DE: 1229 Reference systems
DE: 1244 Standards and absolute measurements
DE: 1247 Terrestrial reference systems
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting