Quality assessment of TanDEM-X Raw DEMs oriented to a fusion with CartoSAT-1 DEMs

Kurzfassung

This paper addresses a quality assessment of TanDEM-X standard Raw DEMs, with a resolution of 12 meters, for three different terrain configurations: urban areas, moderate topography and complex topography. The analysis is performed in the geospatial and in the spectral domain. Beside TanDEM-X, the same analysis is also carried out for CartoSAT-1 and LiDAR DEMs. The latter one is used as a reference. Nevertheless, the focus is centered on TanDEM-X, whose geometric limitations and their impacts on the DEM are analyzed here in detail. How the DEM appears in layover, shadow and phase unwrapping error areas is one of the objectives of the paper. The chosen test site is around Terrassa/Barcelona (Spain), offering all kinds of terrain variations. The final scope of the analysis is to learn about the potentials and the limitations of the two systems, radar (TanDEM-X) and optical (CartoSAT-1), in a way to optimally fuse them and to create an enhanced DEM. A simple fusion processing chain, based on a weighted average depending on the quality of the DEMs adapted to the local geometry, is tested. First results show that in urban and complex terrain areas the improvements are limited, mainly due to the previously analyzed geometrical issues, whereas in moderate terrain areas the enhancement is significant, with a drop in the RMSE of about 25% for TanDEM-X and 30% for CartoSAT-1.