Test Field for Insar Urban Subsidence Studies

Advanced INSAR techniques using stable targets on the ground, such as buildings, have been successfully applied to deformation studies in city areas. However, in some cases high-quality reference measurements have not been available and the validations of the INSAR results have been based on data that probably is not adequate for this purpose. In 2005 the Finnish Geodetic Institute (FGI) established an INSAR test field in the city of Turku. The FGI test field is approximately 5 km long and it is located in the main subsidence area along the river Aurajoki. It comprises roughly 100 bolts in the stone foundations of the buildings and three benchmarks in bedrock. In this paper, aspects of a good INSAR test field design are discussed, and the problems encountered during the establishment of the test field are described. In addition, precision of INSAR measurements based on stable targets is discussed.