Urban land subsidence studies in Finland using synthetic aperture radar images and coherent targets

Ground subsidence is a known problem in several cities in the Europe causing difficulties for urban planning, and occasionally, severe damages for existing buildings. In Finland, even though subsidence problems have been detected in the city of Turku and Helsinki, however, extensive information about phenomena does not exist. Synthetic aperture radar (SAR) interferometry enables the observation of large areas and it has been successfully applied to measure ground deformations in various parts of the world. Heavy vegetation in Finland complicates the use of the INSAR technique. This study, however, showed that advanced interferometric techniques could also be applied in northern vegetated city areas. The subsidence areas were clearly visible in the deformation map, which was formed using a long time series of SAR data and an advanced INSAR algorithm. The INSAR deformation rates agreed well with the levelling measurements that have been carried out in the area and as well as with the soil data.