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Discussion on different interferometric coherence optimization methods

Elise Colin (1), Walid Tabbara(2) , and Cecile Titin-Schnaider(1)

(1) ONERA-Palaiseau, Chemin de la Huniere, 91761 Palaiseau Cedex, France
(2) L2S-CNRS, Plateau de Moulon, 91190 Gif-sur-Yvette, France


The interferometric coherence optimisation methods are based on the definition of so-called projection vectors, which is the way to combine the information occurring from the polarimetric channels of both interferometric images. An important point is the physical interpretation of the projection vectors in terms of scattering charateristics. An optimisation algorithm has been first proposed by Cloude and Papathanassiou, based on the selections of the best pair of projection vectors. The Cloude and Papathanassious algorithm leads to a 3X3 complex eigenvector problem, each projection vector representing a selected mechanism for one image. First we prove that the Cloude and Papathanassiou algorithm corresponds mathematically to the most general optimisation of the interferometric coherence. This means that the interferograms formed by using these mechanisms have the highest possible coherence. Nevertheless, a major drawback of the Cloude and Papathanassiou algorithm is that in neighbouring resolution cells the optimal scattering mechanisms can vary significatly, introducing discontinuities into the extracted height differences. Moreover, the Cloude and Papathanassiou algorithm does not fix uniquely the phase difference between the two projections vectors. Although an additional condition can be freely fixed, an attempt to apply the Cloude and Papathanassiou algorithm to a selected set of our data led to an inexploitable height mapping. In this paper an alternative coherence optimisation algorithm using the same projection vector for both images is proposed. This method is tested and compared with the first one in terms of physical interpretation and results; the properties of the projection vectors obtained by both methods are discussed. Finally, some tests have been been carried out in order to assess the height estimations obtained from both methods.


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