DEM reconstruction in SAR interferometry: practical experiences with ERS-1 SAR data

SAR interferometry is a technique to estimate the topography of the sensed scene extracting the phase difference of the signals received by two antennas carried by the same platform or taken, by one antenna, during two parallel orbits. A relevant processing problem is related to the reconstruction of the absolute phase and height from the wrapped phase differences. Many authors have proposed phase unwrapping algorithms for this purpose but, since the sensed area contains lay over zones and regions with low coherence value, the output consists of a number of “closed regions” with proper phase behaviour. For this reason reconstruction algorithms need, at least, one reference point for each not ambiguous phase sequence related to each zone, to determine the absolute height over the whole area. A technique is presented to reconstruct large areas, using the coherence information for the unwrapping and the correlation of heights in ground range. The software tool developed for interferometric processing, has been applied to ERS-1 SAR scenes of the Orosei Gulf of Sardinia (Italy)