Long-Term and Seasonal Subidence Rates in Urban Areas from Persistent Scatterer Interferometry

As it is well known, space-borne radar interferometry (InSAR) is an appealing and powerful technique to measure the earth's topography and surface deformation with high accuracy and high spatial coverage and sampling. Even though the potential of InSAR was extensively proven within the last years and has been widely recognized throughout the scientific community, its value and applicability to geodynamic monitoring problems is severely limited by the influence of temporal decorrelation and electromagnetic path delay variations. The invention of the multi-image Persistent Scatterer (PS) technique in the late 1990's was a big step forward towards a high accuracy observation of slow surface motion and object deformation over long temporal time spans as it enables the identification, isolation, and estimation of millimeter surface deformation processes from space. This approach proves to be particularly suitable for the observation of the deformation regimes of cities from wide (deformation of extended areas) to small scales (deformation of isolated buildings). In this paper the functionality and the basic workflow of the original PS technique is described. Starting from this overview, every processing step is explained in detail and recent advances are mentioned. Based on this the performance of Persistent Scatterer Interferometry to measure linear as well as nonlinear surface deformation with high accuracy and high spatial sampling is exemplified by a case study from the city of Munich. A summary and an outlook concludes the paper.