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Proceedings Paper

Synthetic aperture radar interferometry: a Markovian approach for phase unwrapping
Author(s): David Labrousse; Stephane Dupont; Marc Berthod
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Paper Abstract

Observation of interferometric images provided by Synthetic Aperture Radar satellites enables the reconstruction of Digital Elevation Model of an area. The elevation of a ground point is computed from the interferogram which is the phase difference of two signals backscattered from the same point and emitted from two different positions of the satellite. Since the phase difference may only be measured module 2 (pi) , the problem consists of estimating the unwrapped phase for each point, that is the number of complete cycles of the phase. Here, we present a solution for this problem which is based on a Markovian approach allowing a combination of global and local constraints. As in regularization technics an energy function is defined as the sum of two potential functions. The first potential measures an error with respect to an a priori model (here, the membrane model). The second potential measures an error with respect to the data (i.e. the interferogram). The optimal labeling with respect to this non-convex energy is then computed by a simulated annealing process. The computational cost of this relaxation technique is particularly heavy in phase unwrapping. This is due to the residual gray level difference between the unwrapped phase image and the data. Therefore, we first employ a deterministic algorithm, which is faster but may propagate some errors, before applying our stochastic algorithm which should correct most of those errors. This algorithm was implemented on the Connection Machine CM-200 and applied on numerous examples presenting cases of discontinuities. The results are quite satisfactory from many points of view: robustness, sensitivity to noise and presence of discontinuities.

Paper Details

Date Published: 5 July 1995
PDF: 7 pages
Proc. SPIE 2486, Integrating Photogrammetric Techniques with Scene Analysis and Machine Vision II, (5 July 1995);
Show Author Affiliations
David Labrousse, INRIA Sophia-Antipolis (France)
Stephane Dupont, ISTAR (France)
Marc Berthod, INRIA Sophia-Antipolis (France)

Published in SPIE Proceedings Vol. 2486:
Integrating Photogrammetric Techniques with Scene Analysis and Machine Vision II
David M. McKeown Jr.; Ian J. Dowman, Editor(s)

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