This paper describes an InSAR (Interferometric SAR) processing system which we developed for obtaining accurate interferogram, Digital Elevation Model (DEM) and Differential Interferogram. There have been proposed many methods for deriving these products from SAR raw data. In the most of former methods, the co-registration was made using a linear function of the range pixel and the azimuth line. The linear function is, however, insufficient to represent local disparities around peaks or valleys. In the proposed system, two Single Look Complex (SLC) images to be co-registered are divided into many triangles so that vertices of these triangles are the corresponding points obtained by the offset measurement process. After the division, images are co-registered by applying Affine transformation to each triangle pair. The piecewise co-registration removes disparity at least on the corresponding points. On the other hand, only the nominal value of the baseline length is currently provided for the interferometric processing. The fixed value, however, does not represent non-parallel orbits from which raw interferogram is obtained. The ambiguity causes the geometrical distortion in DEM and the apparent displacement in the result of differential InSAR processing. The system derives coefficients of both functions for baseline length and for inclination angle by fitting the local disparities to a geometrical model.
Using the system, the accuracies of both coherence image and interferogram derived from actual SAR raw data were successfully improved. The baseline estimated by the system reduced apparent displacement in differential interferogram to 1/10 of that yielded by the nominal baseline.
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