Alpine Digital Elevation Models from Radar Interferometry - a Generic Approach to Exploit Multiple Imaging Geometries

The generation of Digital Elevation Models (DEMs) from Synthetic Aperture Radar Interferometry (InSAR) has developed rapidly in the last 10 years. This new method proofed to be operational with the global success of the Shuttle Radar Topography Mission in the year 2000 and with several companies offering regional topographic mapping campaigns based on airborne InSAR today. However, the current radar systems and the current processing methods will deliver robust results only over moderate terrain. When confronted with steep mountains or canyons, the measurement principle poses a number of problems that are quite hard to solve. The reason being the radar viewing geometry that limits the range of observable terrain slopes in one acquisition and the problem to unwrap the ambiguous phase, a measure for the radar look angle. The paper shows examples from the Shuttle Radar Topography Mission in mountainous terrain and demonstrates some specific deficiencies. Then, some processing techniques are sketched that can help to achieve improved results with available data. Finally, techniques for future high resolution InSAR DEM missions are proposed to minimize the artefacts in mountainous terrain and to actively use multi-angle, multi-frequency observations for more robust and more complete DEM reconstruction.