)An Algorithm for Slope Estimation from Repeat Tracks of ICESat/GLAS

Objective A slope estimation model and algorithms were advanced based on the repeat ground track el-evation data collected from the Geoscience Laser Altimeter System(GLAS)on board the Ice,Cloudand land Elevation Satellite(ICESat).Innovative algorithm steps show and confirm the referencestarting point(RSF)on the reference track(RT)and the corresponding starting point(CSF)on otherrepeat corresponding track(CT).The slope model and algorithms were validated with the elevationdata from ground track 420collected by ICESat/GLAS when passing over the Beijing area during2003-2009.The RMS and standard deviation of slope differences between RT and CTs were deducedand discussed.The results show that the RMS and standard deviation(STD)of the slope differencesincrease with the increase in the STD/RMS of the separation between the CT and RT.The slopedrawing on a geographic map were coincidental with the geographical ground truth when comparedwith an image obtained from Google map.The calculated slope based on ICESat/GLAS data was com-pared to that based on SRTM DEM data demonstrating the reliability of these results.