Synthetic Aperture Radars offer the possibility of earth imaging notwithstanding night or weatherconditions. As the penetration of the electromagnetic waves in arid terrain could reach meters,SAR instruments can reveal paleo rivers in a desert. Also, SAR’s can measure travel times andthus distances, generating not only good digital elevation models, but also terrain models as thevegetation canopy can be penetrated. Finally, if the radar targets are temporally stable, thentheir millimetric motion can be measured allowing co-seismic motion studies, inflation - deflationof gas storage reservoirs, dams motion due to water filling, etc.Numerous public and private constellations of these sensors are nowadays available and theiruse is more and more common.