Detection of terrain changes in southern Denmark using persistent scatterer interferometry

Since 1991, a number of European satellites have acquired data of the Earth’s surface for environmental monitoring. In general, a satellite will orbit the Earth in about 11⁄2 hours and it takes 35 days before an ERS or ENVISAT satellite repeats radar scanning of the same position. For younger generations of satellites, such as RADARSAT and TERRA, the scanning repeat interval has decreased to 24 and 11 days, respectively, so that hundreds of radar scenes of the same place, produced over the past c. 20 years, are now available. Persistent scatterer interferometry (PSI) is a remote-sensing technique for measuring and monitoring land deformation that uses these radar scenes (Ferreti et al. 2001). The technique can be used to assess natural ground movements and displacement of man-made constructions. Over the next three or more years the Geological Survey of Denmark and Greenland (GEUS) will participate in three satellite monitoring projects conducted under the auspices of the European Union. They are all funded under the Global Monitoring Environment System (GMES). The first project, which is the subject of this paper, is named TerraFirma and started in 2003 as a European Space Agency GMES service project. The second project, funded by the 7th Framework Programme, is named SubCoast, and it will monitor subsidence in coastal areas. In Denmark, it will concentrate on the southern part of the island of Lolland. Finally a large monitoring project named PanGeo with similar funding has begun early in 2011. Twenty-seven European geological surveys participate in PanGeo that focuses on ground movements in urban areas. Two cities in each of the participating countries are selected as targets for PSI analysis. Concerns about the effects of global climate changes are the main motivation for the GMES support to the satellite monitoring projects. The TerraFirma project was extended with an additional three years of research and development and will continue until 2012. The project has five themes: (1) tectonic movements, (2) hydrological conditions, (3) flooding, (4) subsidence in abandoned mining areas and (5) wide-area satellite scanning. GEUS is involved in the flooding theme dealing with the increased risks of flooding of the low-lying areas in south-west Jylland, adjacent to the Danish Wadden Sea (Vadehavet). The main environmental and constructional concerns are the dykes that protect the low land areas along the coast of Vadehavet. In order to improve risk management Detection of terrain changes in southern Denmark using persistent scatterer interferometry