Questioning the effects of raster-resampling and slope on the precision of TanDEM-X 90 m digital elevation model

Defining watersheds with enough topographical features is crucial when large infrastructure projects are concerned. German Aerospace Center (DLR) recently announced the dissemination of the 90 m variant of the original global TanDEM-X 12 m Digital elevation model (DEM). It was announced as produced with a special averaging technique, which would even surpass the precision of the 12 m DEM. This study aimed to test this claim while simultaneously testing whether resolution coarsening would deteriorate the performance of a higher precision DEM. AW3D30 was used as auxiliary data in four sites. Results confirmed that the 90 m DEM was indeed highly reliable at or below 20% slopes in two investigated dam reservoir areas with gentle terrain conditions, and overestimated in other two dam reservoirs with severe topography. The resampling approach did not necessarily worsen the elevation values aggregated into a larger raster resolution as obvious from the auxiliary data analyses.