Interferometric DEMs in alpine terrain-limits and options for ERS and SRTM

With ERS tandem data being today's primary interferometric data source, DEM generation is currently limited to moderate terrain. In general, layover and shadow affect the visibility and resolution of SAR sensors in rugged terrain. As a consequence, classification and phase unwrapping of such data is difficult. Shuttle Topography Mission SRTM X-SAR data is expected to give better results due to its viewing geometry and the high coherence, but it might still suffer from the problem under extreme conditions. The authors perform a quantitative analysis of the radar illumination conditions, using a digital elevation model. The potential benefit of combining data from different viewing geometries like incidence angle and orbit inclination are shown.