Rail-borne SAR interferometry for Disaster Prevention

Major railway disasters, such as line or infrastructure collapse, rock or water fall on the tracks, are often foreannounced by unnoticed precursors such as minute deformation of walls or water infiltration. ONERA & SNCF conducted a first experiment of change detection using cross-track interferometry & coherent change detection with a rail-borne synthetic aperture radar. The BuSARd airborne SAR pod was strapped on a flat wagon with its X-band horn antennae extended to the wagon corner in squinted across-track configuration. Preliminary results from a first set of acquisition trips allowed to assess the specific difficulties of SAR in this application. Compared to space/airborne SAR major difficulties are consequences of an extremely wide relative swath width (propagation gain range of 40 dB), a large angular baseline (at near range) & wider variation of along-track velocity (slowdown/stop for traffic regulation).