WU Peng-fei, LIU Lin, QIAO Xiao, ZHOU Jie, LIU Jin-tao, LI Xiao-peng, HAN Xiao-le
The accuracy and resolution of the Digital Elevation Model (DEM) affect the results of terrain analysis, and such effect is particularly evident in plateau and high mountains. With a hillside slope in the Duodigou watershed which is a sub-basin of the Lhasa River Basin as study object, we examined the abilities of three types of DEM data in reflecting the real terrain of typical profiles. As the analysis shows, in the high mountains of the Qinghai-Tibet Plateau, the SRTM and ASTER GDEM data have overestimated the elevation of the bottom of the valley and lost terrain features, while the DEM obtained using LiDAR (Light Detection And Ranging) technology can accurately reflect the actual terrain. We elaborated the terrain features, inclusive of slope gradient, plane curvatures and profile curvatures, of LiDAR DEMs of eight resolutions (1 m, 2 m, 5 m, 10 m, 15 m, 20 m, 25 m, 30 m) by means of local variance. We found that DEMs of low resolutions have lost much topographical information in high mountains, causing attenuations of the terrain and changes in the microtopography of hillsides. In order to avoid the distortion in high mountain areas, we further gave the minimum resolution for studies of slopes or curvatures. The resolution of DEMs used in slope studies should be higher than 5 m, and the optimal resolution for curvature studies is 1 m. The study has shown that the use of LiDAR technology to extract high-resolution DEMs has a promising application prospect in high mountains of the Qinghai-Tibet Plateau.
