NepalDTM: A National 8-Metre Bare-Earth Digital Terrain Model of Nepal from Multi-Source Satellite Data Fusion

Achyut Paudel

NepalDTM is an open bare-earth elevation model of Nepal stored on an 8 m grid. Where the NASA High Mountain Asia 8 m stereo mosaic has a usable height, that mosaic is the surface. Elsewhere the surface is Copernicus GLO-30. A histogram gradient-boosting model, trained on 6,230,548 ICESat-2 points and 7,035,904 GEDI points, predicts how far the surface sits above the ground and subtracts that height. On 4,463,463 held-out ICESat-2 points inside Nepal, with whole 48 km blocks left out of each training fold, the root-mean-square error is 6.10 m (NMAD 2.61 m, bias -0.15 m). The same points give 9.07 m for Copernicus GLO-30, 8.47 m for GEDTM30, and 7.78 m for FABDEM. The error is 1.96 m below 300 m and 8.27 m between 2.5 and 4 km. Independent differential GPS on the Khumbu surface agrees to 2.49 m RMSE at glacier margins. Inside the delivered grid, 37% of the area uses the 8 m mosaic and 63% is Copernicus fill, so the posted spacing is not 8 m terrain detail on every cell. The tiles, the figures, and the code that rebuilds the model are public.