Recent advances on surface ground deformation measurement by means of repeated space-borne SAR observations

Space-borne Synthetic Aperture Radar interferometry (INSAR) is a well known widely used remote sensing technique to get precise (sub-centimetric) surface deformation measurements on large areas (thousands of km2) and high spatial density of measurement points (hundreds per km2). In this work the recent technological advances of this technique are presented. First, a short review of the INSAR basics is dedicated to readers who are not INSAR specialists. Then, an analysis of the improvement of ground motion measurement offered by multiple repeated space-borne SAR observations gathered by the new generation of high resolution SAR systems is given. An example obtained with the recent German TERRASAR-X system is shown and compared with the measurements obtained with the elder C-band RADARSAT-1 system. Finally, a possible processing of multi-temporal analysis of SAR images that allow extracting ground motion information also from partially coherent targets is given. In this case the core idea is to relax the restrictive conditions imposed by the Permanent Scatterers technique. The results obtained in different test-sites show an increased spatial density of areal deformation trend measurements, especially in extra-urban areas at the cost of missing motions with strong velocity variation.