Vertical accuracy of digital elevation model from Shuttle Radar Topographic Mission - a case study

Vertical accuracy of the processed Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM) was evaluated using spot height as well as reference DEM. Terrain dependency of error was also explored in relation to elevation, slope and aspect of the terrain. The positive mean error (6.77 +/- 1.79 m) indicated that the SRTM DEM was slightly underestimating the elevation and this pattern gradually increases towards higher elevation. The observed root mean square error (RMSE) (27.58 +/- 4.22 m) for the region do not fulfill the 16 m RMSE specification of the SRTM mission. High magnitude errors are typical to steep slope (due to overestimation) and in stream valley (due to underestimation). The magnitude of residuals for NW, W and SW facing slope was smaller as compared to their complementary angle. Results also indicated a S and NE components in SRTM DEM because of underestimation and overestimation of elevation, respectively.