InSAR enables ground motion detection

The so-called 'Permanent Scatterer' method of Synthetic Aperture Radar Interferometry (InSAR) involves combining multiple radar images of the same location, using 'stable scatterers' such as rock outcrops or buildings to avoid signal decoherence and make measurements of millimetre-scale ground shifts occurring between acquisitions. Permanent-Scatterer InSAR is at the basis of the SLAM project in Italy, aimed at better quantifying landslide hazard and employing a decade's worth of archived satellite data. Here permanent scatterer measurements are overlaid on a Spot 5 image and wrapped on a digital elevation model.