Polarimetric Interferometry and Differential Interferometry

This Lecture mainly based on [1, 2] presents the role of Polarimetry in SAR Interferometry. A general formulation for vector wave interferometry is presented that includes conventional scalar interferometry presented in the respective former lecture as a special case. Based on this formulation, the coherence optimization problem can be solved to obtain the optimum scattering mechanisms that lead to the best phase estimates. Comparison with conventional single-polarization estimates illustrates the significant processing gains that are possible if there is access to full polarimetric interferometric data. A comparison with conventional single-polarization presented in former lectures illustrates the significant processing gains that are possible if access to full polarimetric interferometric data is possible. The strong polarization depends of the coherence will be addressed and the analytical solution for optimum polarization states that maximize the interferometric coherence will be derived and applied to experimental data. These improved interferogrammes allow an improvement of the accuracy of derived DEM products. The introduction of a new coherent decomposition theorem for interferometric applications based on the Singular value spectrum of a 3 x 3 complex matrix allows the decomposition of polarimetric interferometric problems into a set of coherent scattering mechanisms. As a consequence, it is possible to generate interferograms related to certain independent scattering mechanisms and extract the height differences between them. The limitation of this technique is the existence of independent scattering mechanisms located at different height positions. To explain the physical origin of these mechanisms, a coherent electromagnetic scattering model will be established which, additionally, can be used to establish the suitability of the decomposition algorithm for solving the problem of estimating the location of the effective scattering center, which is a critical point in the physical interpretation of interferograms. However, these introduction of Polarimetry in interferometric processing requires that fully coherent polarimetric data must be collected in order to separate the scattering mechanisms.. In this connection polarimetric Differential Interferometry will be considered also. The phase difference between the optimum interferograms obtained by the application of the algorithm on the SIR-C data turned out to be strongly correlated with the actual forest height. This was a major result indicating the potential of the coherent combination of polarimetry and interferometry. [1] Cloude, S.R.”Polarimetric SAR Interferometry”, IEEE Trans.GRS. vol. 36. no. 5. September 1998 [2] Cloude S.R, and K.P. Papathanassiou. “Polarimetric SAR Interferometry.” IEEE Trans. Geosci. Rem. Sens., vol. 36, no. 5, pp. 1551-1565, September 1998.