Two examples of the use of SAR interferometry on displacement fields of small spatial extent

Interferometric combination of pairs of SAR images acquired by the European ERS-1 satellite maps deformation fields associated with two phenomena, both of small spatial extension and located in SE France: the one is rapid terrain deformation caused by a landslide near the city of Saint Etienne de Tinee, and the other is slower subsidence caused by underground coal mining near Gardanne. Unlike interferometric measurement of wide-field deformation, atmospheric propagation heterogeneity is not an accuracy-limiting factor. Although the radar data confirm prior knowledge concerning the landslide, such an application of SAR interferometry appears difficult under normal conditions of observation using current spaceborne radar systems. The study of soil subsidence, however, can be generalized and improves prior knowledge of the displacement field, which has here been modeled assuming elastic deformation in a half-space from several sources. The two examples help to understand the limits of the interferometric technique.