An algorithm for phase-offset evaluation in InSAR DEM generation

Synthetic Aperture Radar Interferometry (InSAR) is a technique for the generation of Digital Elevation Models (DEMs) of an observed scene. It exploits the phase difference (interferogram) of two SAR images relevant to the same area and acquired by two different look angles. To recover the topographic information from an InSAR data pair, it is necessary to evaluate a proper phase offset value to add to the unwrapped SAR interferogram. Generally, such a phase offset is accurately estimated by using Corner Reflectors (CRs) properly deployed over the illuminated area. Nevertheless, in some cases of practical interest, CRs cannot be used: in order to overcome this limit, different algorithms have been proposed in literature. In this paper, we present an algorithm aimed at estimating the InSAR phase-offset without using CRs. To this aim, we first present a theoretical analysis, validated by experiments carried out on simulated data, for the evaluation of the phase offset and, thereafter, we apply the proposed method on real data acquired by the X-band airborne OrbiSAR system. Comparisons with results achieved by using CRs properly deployed over the test site are also included.