Corner reflectors and multi-temporal SAR inteferometry for landslide monitoring

The application of Persistent Scatterer Interferometry (PSI) to slope instability monitoring poses challenges related to the complex kinematics of the phenomenon, as well as to the unfavourable settings of the area affected by landslides, often occurring on sites of limited extension, characterized by steep topography and variable vegetation cover. New-generation SAR sensors, such as TerraSAR-X (TSX) thanks to their higher spatial resolution, make PSI applications very promising for monitoring areas with low density man-made. Nevertheless, the application of techniques still remains problematic or impossible in rural and mountainous areas. This is the case, for instance, for the Municipality of Carlantino, in Southern Italy. Both C-band medium resolution SAR data from ESA satellites, and X-band high resolution SAR data from the TSX satellite, were processed through the PSI algorithm SPINUA. Despite the higher spatial density of PS from TSX, the landslide body is lacking coherent targets, due to vegetation and variable land cover. To allow stability monitoring, a network of six CRs was designed and deployed over the landslide test site. Twenty-six TSX stripmap images were processed by using both PSI and an ad hoc procedure based on double-difference analysis of DInSAR phase values on the CR pixels, constrained by the accurate CR height measurements provided by DGPS. Despite the residual noise due to the sub-optimal CR network and the strong atmospheric signal, displacement estimation on the CRs allows to propagate the PSI results downslope, proving the stability of the landslide area subjected to consolidation works.