Calibration Requirements for Airborne SAR Interferometry

摘要

One of the main limitation on the use of SAR interferometry to automatically generate Digital Elevation Models (DEM) is related with both the accurate calibration of the system parameters and its stability from flight to flight. The unstable movements of an airborne SAR platform can be corrected during the processing step, as long as those movements are recorded in an accurate manner. Errors and time drifts in the system parameters or on the plane position and attitude measurements lead to geolocation errors in the final DEM. A calibration method based on the so-called "sensitivity equations", which relate the target location error with the error on the estimation of the system parameters, is described. The equations have been derived by differentiating the interferometric geolocation equations in closed form for the most general case in a squinted geometry. The interferometer parameters considered are the baseline length and elevation, common time delay, interferometric constant phase, plane position and attitude angle offsets, etc. The equations can be used to both calibrate a single DEM from different ground control points (GCP) spread along the swath and the full interferometer from well-known located corner reflectors (CR).