Cost-Effective Global Deformation Monitoring Using Ambiguous Staggered SAR and Permanent Scatterer Interferometry

Permanent scatterer interferometry (PSI) is an established technique that enables the retrieval of deformations with meter spatial resolution and subcentimeter accuracy from stacks of synthetic aperture radar (SAR) images. However, the exploitation of this technique for global monitoring places very high demands on the mapping capability of the SAR instrument and mission. Based on the observation that deformation can still be retrieved with similar accuracy using SAR images corrupted by significant disturbance, this letter proposes a dedicated ambiguous staggered SAR mode that combines beam shaping in elevation, alternation of orthogonal waveforms, and continuous variation of the pulse repetition interval (PRI). This mode achieves meter resolution over ultrawide ground swaths of over 600 km at a total disturbance level of less than 10 dB without the use of digital beamforming (DBF) or multiple apertures. As a result, the mapping capability for deformation monitoring of a satellite like TerraSAR-X can be increased by a factor of over 20 without any noticeable degradation in performance and with a considerably smaller data volume per unit of mapped area. The theoretical arguments are supported by analyses of stacks of TerraSAR-X images acquired over Mexico City, Mexico. This concept paves the way to a new strategy for cost-effective Earth monitoring based on frequent, low-quality SAR observations.