Validation of ERS differential SAR interferometry for land subsidence mapping: the Bologna case study

The city of Bologna, Italy, is ideal to assess the potential of ERS differential SAR interferometry for land subsidence mapping in urban areas for a couple of reasons: the subsiding area is large and presents important velocities of the vertical movements; there is a typical spatial gradient of the vertical movements; many ERS SAR frames are available; a large scientific community is involved in the study of subsidence; a large amount of levelling data is available. The authors analyze a time series of ERS-1/2 data from August 1992 to May 1996 and compare the subsidence maps derived from ERS SAR interferometry and levelling surveys. The authors conclude that for the mapping of land subsidence in urban environments ERS differential SAR interferometry is complementary to levelling surveys and GPS with regard to cost effectiveness, resolution and accuracy.