Land subsidence in Lisbon area: validation of PSInSAR results

Abstract

Land subsidence in the Lisbon area was detected during the first stage of Terrafirma, a service of ESA-GMES Element Programme, dedicated to detect and measure Earth-surface terrain motion from satellite radar interferometry (InSAR). Two large areas were identified, each one covering several square kilometres, which presented subsiding rates of several millimetres per year. One of these areas was used as a study case concerning validation of the InSAR results. Two geodetic techniques, GNSS and geometric levelling, independent from PSInSAR, were used in the validation. The paper includes a description of the area under study, namely the known geology and human use, and presents the results from permanent scatterer SAR interferometry (PSInSAR), a GNSS station and two levelling lines that cross the area.