Early detection and in-depth analysis of deformation phenomena by radar interferometry

The spaceborne differential interferometric SAR (DInSAR) technique may play an important role in the measurement of land deformation phenomena, especially in urban, suburban and industrial areas. In order to fully exploit its capabilities and increase its operational use, this paper proposes two complementary levels of analysis. The first one is a comprehensive low-cost screening, in order to detect unknown subsidence phenomena over large areas. This analysis, which provides a first estimation of deformations, has to be performed using a limited set of SAR images. The second level includes an in-depth quantitative analysis based on large image stacks, which requires more image acquisition and data processing resources. This type of analysis can be typically used to study deformation phenomena of special relevance, where an effective support to the decision-makers requires a fully quantitative estimation of deformations. The two levels of analysis were proved over a test area of about 2100 km2, located in Catalonia (Spain). Without any a priori information, seven deformation phenomena were detected using a reduced set of interferograms. Furthermore, the quantitative analysis of a subsidence of small spatial extent, which was based on ascending and descending datasets, confirmed the capability of DInSAR to quantitatively assess deformation phenomena.