21 December 2000 Geolocation algorithms for SAR interferometry
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Abstract
Three measurements are required to reconstruct the topographic information by means of Synthetic Aperture Radar Interferometry (InSAR): range, azimuth, and elevation. The first is obtained by timing the return of the radar pulse, the second by observing its Doppler frequency shift, and the third by measuring the phase difference between signals recovered at the spatially displaced antennas. In this paper a new general scheme for the geolocation of InSAR information is presented. It avoids the use of an Earth model and exploits the full information of a SAR interferometer: orbit data, range and Doppler frequency shift of each SAR image, and interferometric phase. Two geolocation algorithms are obtained within this scheme. The former studies the geolocation as the intersection of five surfaces defined by measurements of range, Doppler frequency shift and interferometric phase. In particular, the five surfaces are: the range spheres centered at the SAR antennas which is also where the Doppler frequency shift cones are located. The interferometric phase adds another surface - a phase hyperboloid - whose axis of symmetry is the interferometer baseline. These five surfaces intersect at two locations in space. One of them is the geolocation of image pixel. The last geolocation algorithm is based on the solution of a set of four equation: the range spheres and the Doppler frequency shift cones of the two SAR images. An exact closed-form solution is obtained. This solution does not rely on approximations and avoids the use of iterative algorithms. This results in a reduction of the computational load. Moreover, the proposed algorithms give a scheme for computing the geolocation accuracy.
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Giovanni Nico, Giovanni Nico, } "Geolocation algorithms for SAR interferometry", Proc. SPIE 4173, SAR Image Analysis, Modeling, and Techniques III, (21 December 2000); doi: 10.1117/12.410660; https://doi.org/10.1117/12.410660
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