A Method to Estimate Long-Wave Height Errors of SRTM C-Band DEM

The digital elevation model (DEM) of the Shuttle Radar Topography Mission (SRTM) still has known long-wave height errors. These errors occur especially in the continent's interior with a spatial scale of hundreds to thousands of kilometers and a magnitude of several meters. In this letter, for the first time, a method for estimating those long-wave height errors with the intention to improve the absolute height accuracy of SRTM C-band DEM globally is presented. The improvement of the SRTM DEM bases on continuously defined spherical harmonics which are able to model the whole sphere. The highly accurate measurements of the Geoscience Laser Altimeter System instrument aboard the Ice, Cloud, and land Elevation Satellite (ICESat) serve as input for the least-squares adjustment which estimates the relevant coefficients of the spherical harmonics. Selection criteria are applied to these data to get ICESat points on flat and nonvegetated areas which account for the most “reliable” points with an accuracy of approximately 1 m. Our results provide a height improvement of 5-6 m along Eurasia and up to ±4 m along North America. The validation with worldwide Global Positioning System tracks proves that the absolute height accuracy of SRTM could generally be improved to better than 3 m.