SAR processing in the temporal domain: Application to direct interferogram generation and mountain glacier monitoring

Synthetic aperture radar (SAR) interferometry has the potential to measure temperate glacier displacement with a large coverage of the surface compared with pointwise terrestrial ground measurements. The significant topographic relief in mountainous areas, however, where most alpine glaciers are located, makes the use of SAR imagery rather difficult. Among the difficulties, when the resolution increases, the focusing of satellite SAR images, usually performed in the frequency domain with a constant-height hypothesis, becomes a critical issue. SAR processing in the temporal domain is a different approach that enables the use of information such as the local topography. In this paper, we present an original method to perform this temporal domain focusing by modeling the relative motion of the satellite and Earth points. The method allows production of SAR single look complex (SLC) images directly in ground geometry and reduces the need for resampling and phase correction to obtain interferograms. A tandem pair of European remote sensing (ERS) SAR images acquired over the Mont-Blanc area is used to illustrate the proposed approach. The results are presented with amplitude images and interferograms measuring glacier 1 day displacements and are compared with the results from the differential interferometric automated process applied to survey of nature (DIAPASON) and repeated orbit interferometry package (ROI–PAC) conventional SAR processors.