Experiences with Multiresolution and Multifrequency InSAR Height Model Generation

Interferometric synthetic aperture radar (InSAR) has become a broad field encompassing the use of both airborne and spaceborne sensors operating at a range of wavelengths and resolutions. This paper derives general conclusions from experiences at the Remote Sensing Laboratories of the University of Zürich with a variety of airborne and spaceborne InSAR sensors. Results from multiple systems operating at a variety of radar wavelengths are reviewed. For test sites in Switzerland, single-pass airborne InSAR-generated DEMs with resolution of approximately one metre are compared with references generated both photogrammetrically and through laser scanning. DEMs generated using satellite-based InSAR (at different wavelengths) are compared with reference elevation models derived from digitized topographic maps. Airborne dual-antennae systems offer low-cost, high resolution, single-pass coverage. Simultaneous acquisition with two antennae ensures uniformly high coherence, exceptions being extremely radar dark (e.g. shadow) areas. Using highly accurate differential GPS, no ground control points (GCPs) are required, making automated processing possible. Airborne systems also allow flexible choice of acquisition geometry, free of the fixed ascending/descending duality inherent in spaceborne SAR imagery. Airborne and spaceborne InSAR offer complementary technologies. Upcoming generations promise some relief from remaining weaknesses.