HR: 12:05h
AN: B42B-07    [Abstracts]
TI: Optimization of Geoscience Laser Altimeter System Waveform Metrics to Support Vegetation Measurements
AU: * Miller, M E
EM: memiller@cnr.colostate.edu
AF: Colorado State University, Forest Rangeland and Watershed Stewardship 1472 Campus Delivery, Fort Collins, CO 80523, United States
AU: Lefsky, M
EM: lefsky@gmail.com
AF: Colorado State University, Forest Rangeland and Watershed Stewardship 1472 Campus Delivery, Fort Collins, CO 80523, United States
AU: Pang, Y
EM: caf.pang@gmail.com
AF: Colorado State University, Forest Rangeland and Watershed Stewardship 1472 Campus Delivery, Fort Collins, CO 80523, United States
AB: The Geoscience Laser Altimeter System (GLAS) has acquired over 250 million individual lidar waveforms over forest regions globally; an unprecedented dataset of vegetation heights. We have demonstrated the ability to retrieve accurate vegetation heights using waveform metrics including vertical extent and transformations of the depth of the waveform's trailing and leading edges. All three indices are highly dependant upon the signal strength and signal-to-noise ratio of the waveform, as the background noise contribution to the waveforms has to be removed before calculation of these waveform metrics. Over the last five years, GLAS has collected data during 12 observation periods using illumination from three different lasers. Power levels of these lasers have varied over time, resulting in variable signal characteristics. To minimize this effect, we optimized a noise effect parameter which varies for each observation period. This parameter is used with the mean and standard deviation of the background noise to create a noise level that is removed from the waveform. The optimization analysis uses a global dataset of waveforms that are near- coincident with waveforms from other time periods; the goal of the optimization is to minimize the difference in vertical extent between these spatially overlapping GLAS shots. Waveforms within 10 m of each other are considered near-coincident; 10 m is small relative to the 70 m diameter of the footprint. Initial optimization results are promising; the relative consistency of the waveform noise characteristics is known and the root mean square error of the difference in vertical extent between overlaps has decreased from 7.6 m to 6.6 m. Further optimization of the noise effect parameter will result in more accurate and precise estimates of canopy height from GLAS.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting