Integrated Use of Advanced InSAR and GPS Data for Subsidence Monitoring

Global Positioning Systems (GPS) and Advanced Synthetic Aperture Radar Interferometry (InSAR) are complementary monitoring techniques. Their integrated use allows to take advantage of the strengths offered by each approach, overcoming their weaknesses. The case study described in this paper presents an interesting integration methodology developed in order to study the subsidence phenomena at regional scale. Arpa (Regional Agency for Environmental Prevention), on behalf of the Emilia-Romagna Region and in collaboration with Tele-Rilevamento Europa) TRE. and the Department of Engineering of the Bologna University (DICAM), has recently updated the regional subsidence map of the Po Plain sector of the region, using the measurement of the vertical displacement obtained with the integrated use of continuous GPS stations and Advanced InSAR data. A SqueeSAR™ analysis of Radarsat radar images acquired between 2006 and 2011, was carried out over the whole regional plain territory, allowing to obtain a map of vertical displacement for more than 2,000,000 measurement points. In parallel, the acquired data from 17 permanent GPS stations were processed in order to calibrate and validate the InSAR results. The final calibrated results has permitted to obtain a complete and homogeneous map of the subsidence phenomena at regional scale, defining a both “absolute” and relative velocity datum with respect to the ITRF (International Terrestrial Reference Frame) and European Terrestrial Reference Frame (ETRF).