Interferometric DEM Reconstruction of Alpine Areas – Experiences with SRTM Data and Improved Strategies for Future Missions

The Shuttle Radar Topography Mission SRTM produced the first global digital elevation model (DEM) data set of the world’s topography in the year 2000. The data set covers regions between ±60 degrees latitude with a resolution of 30 meters. The 90 % height accuracy in these regions is on the range of 6 meters, limited by the baseline length, the metrology and the instrument noise. In mountainous areas larger data gaps exist in the C-band data set produced by NASA/JPL as well as in the X-band data set produced at DLR. The reason for these gaps are high slopes that lead to radar shadow, layover and to phase unwrapping problems. In order to overcome these problems and to further increase the DEM accuracy, future systems must take advantage of multiple incidence angles, multiple heading angles and multiple baselines or multiple radar frequencies. The paper demonstrates high mountain artifacts in SRTM data and demonstrates strategies and algorithms to overcome them. Optimized acquisition strategies for future missions are proposed that are adapted to the slope distribution of the area. The TanDEM-X mission currently studied at DLR and the expected product accuracy is shortly presented.