GEDI: A New LiDAR Altimetry to Obtain the Water Levels of More Lakes on the Tibetan Plateau

Remote sensing is an effective means for lake water level monitoring on the Tibetan Plateau (TP). The purpose of this study is to estimate water levels of lakes on the TP using the Global Ecosystem Dynamics Investigation (GEDI) and Cloud and Land Elevation Satellite-2 (ICESat-2), evaluate the performance of ICESat-2 and GEDI in estimating water levels, and analyze the differences of water level obtained by the two altimeters. The results showed that the average coefficient of determination (R2) values between the estimated water levels (GEDI and ICESat-2) and the datasets (DAHITI and Hydroweb) were greater than 0.80, respectively. The water level of DAHITI and Hydroweb are mainly from radar nadir altimeters. The average root mean square error (RMSE) between GEDI and DAHITI was 0.54 m, between GEDI and Hydroweb was 0.38 m for Qinghai Lake. The average RMSE of Qinghai Lake between ICESat-2 and DAHITI was 0.50 m, and between ICESat-2 and Hydroweb was 0.28 m. The comparison results showed that the accuracy of GEDI seems to be slightly lower than that of ICESate-2. The main impact indicators of the difference between the GEDI and ICESat-2 in lake level estimations were the viewing angles (VAs), solar elevation, air temperature, and wind. From 2019 to 2021, GEDI covered 770 more lakes than ICESat-2, and the lake level fluctuation mainly occurred in the Inner Plateau and Yangtze basins. The GEDI can effectively estimate lake levels, which provides more water levels for lakes and lays a foundation for future research on the TP.