SAR analysis of building collapse by means of the permanent scatterers technique

As already shown in previous papers, detection of stable areas make it possible to use DInSAR techniques to get local measurements on a pixel-by-pixel basis. Reliable deformation measurements can then be obtained on a subset of image pixels, called Permanent Scatterers (PS). These points can be used as a "natural GPS network" to monitor terrain motion in the direction of the line of sight (LOS), analyzing the phase history of each one. In urban areas most of the PS correspond to single buildings whose deformation can be measured every 35 days with an accuracy better than one millimeter. Results obtained ERS SAR images are presented for 3 test sites: Camaiore (40 images), Milano (62 images) and Paris (64 images). Time series analysis of collapsed buildings in Camaiore are illustrated which show interesting precursory motions. Time series analysis of two metallic buildings in Milano and Paris are then used to validate the technique and to estimate its accuracy.