INSAR phase offset estimation for DEM generation: Improvement of the performances of the STopBE and IPBE algorithms

In order to generate a Digital Elevation Model (DEM) by exploiting the Synthetic Aperture Radar (SAR) Interferometry (InSAR) technique, it is necessary to properly estimate an unknown phase offset present in the unwrapped interferogram. To this aim, two deterministic methods, which make use of an external low accuracy DEM, have been recently proposed. Both algorithms, which are named Slope Topography Based Estimate (STopBE) and Improved Phase Based Estimate (IPBE), are based on a Least Squares (LS) inversion exploiting a linear model of the observables. However, in both cases, the LS inversion leads to the design of a filter that, in practice, cannot be implemented due to the inaccuracy of the used external DEM. Accordingly, both the STopBE and the IPBE have to necessarily exploit a noisy version of the corresponding theoretical LS filter. In this work we investigate the effects of this limitation and propose a procedure aimed at reducing them. The presented analysis is validated by means of experiments carried out on different topographic scenarios.