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Alenia Spazio research activities on SAR interferometry

Topographic mapping on whole Earth surface is aimed for a lot of applications. SAR interferometry is the technique for accomplishing topographic mapping using a pair of SAR images of the same area taken from two different points of view separated by a distance called 'baseline.' These points of view can be one or two antennas placed on an airborne platform (double antenna technique) or two passes of the same satellite on two different orbits (double passes technique). This method of acquisition causes the phase of each pixel to be different in the two images. This depends, after having removed the contribution of the different geometry of view, only on the height of the observed point on ground. Alenia Spazio has developed a whole processing technique able to obtain three-dimensional images of the observed area using two complex images (SLC -- single look complex) coming from SAR sensors like ERS-1 and X-SAR. This paper describes the whole processing of the complex SAR data to obtain the 3D representation of the image from a couple of SAR images after proper overlapping. In particular some steps have been pointed out: the evaluation of range and azimuth shifts between the two images; the overlapping of these by a particular interpolation; the filtering of the complex data in order to improve the coherence between the images; the extraction and filtering of the interferogram; the phase unwrapping; the phase-to-height conversion. The whole processing was applied to some images coming from scientific missions: in this paper some results are presented.