Potential of Geodetic SAR for Positioning and Height Monitoring with TerraSAR-X and Sentinel-1

Abstract

Our research in exploiting the inherent ranging capabilities of Synthetic Aperture Radar (SAR) has demonstrated range observations at the one centimeter accuracy level for passive radar reflectors, given that the radar observations are processed by a geometrically accurate SAR processor. Moreover, external disturbances caused by atmospheric path delay (troposphere, ionosphere) and geodynamic displacements (solid earth tides, ocean loading, ...) have to be taken into account. The correction approach follows the concept used in well established geodetic techniques like Global Navigation Satellite System (GNSS) or radar altimetry. By making use of these geodetic SAR observations, direct 3D positioning of specifically designed passive objects (corner reflectors, octahedrons) or active transponders becomes attainable. For TerraSAR-X, the 3D positioning capability has been tested with different passive reflectors and enables an accuracy at the centimeter level. Regarding Sentinel-1, the ranging results reported for the geometrical calibration campaign show encouraging results of approximately 6 cm, and further refinements are currently under investigation. In addition, the feasibility of active transponders as radar targets was successfully demonstrated, making Sentinel-1 another candidate for geodetic SAR applications. The presentation discusses the 3D SAR method in the context of applications, which require an accurate monitoring of the ellipsoidal heights in order to link them to the global geometric reference frame. We give an overview on our SAR methods and state the potential for positioning and height monitoring with TerraSAR-X and Sentinel-1 on the base of selected study regions.