Evaluation of the Vertical Accuracy of Open Access Digital Elevation
Models across Different Physiographic Regions and River Basins of Nepal
Abstract
The vertical accuracy of eight different freely accessible DEMs has been
evaluated across different physiographic divisions and the river basins
of Nepal. Results revealed that MERIT is superior to other DEMs (RMSE
9m) in the low-lying Terai plains of Nepal where the elevation range is
lower. In High mountains and High Himalayas having higher elevation
range, SRTM90m outperformed all its counterparts. Meanwhile, in Siwalik
and middle mountains, both SRTM90m and HYDROSHEDS exhibited almost
similar RMSE indicating their compatible uses in these regions.
Meanwhile, the accuracy assessment across different river basins of
Nepal discerned that the accuracy of SRTM90m was above others in larger
river basins like Koshi (RMSE 224m), Narayani (RMSE 215m), and Karnali
(RMSE 265m) where the range of elevation is greater. In the smaller to
medium-sized basins like Kankai, Kamala, Bagmati, West Rapti, and Babai,
HYDROSHEDS was preferable along with SRTM90m. Based on different error
statistics, the DEMs were ranked in order of their accuracy.