Polarimetric Interferometry

This lecture 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 dependence 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. Introduction Polarimetric SAR Interferometry was a first step in the abatement of the scattering ambiguity problem in the height direction. By combining interferometric and polarimetric techniques, it enables the separation of different scattering mechanisms within a resolution cell and at the same time, the estimation of the associated heights. Both, radar polarimetry and radar interferometry are phase sensitive techniques. The use of polarimetric SAR data has been widely addressed in the last decade. The tight relation between natural media physical properties and their polarimetric features leads to highly descriptive results that can be interpreted by analyzing underlying scattering mechanisms. Interferometric data on the other hand provide information concerning the coherence of the scattering mechanisms and can be used to retrieve observed media structures and complexity. The complementary aspect of polarimetric Martin Hellmann, Shane R. Cloude German Aerospace Center (DLR), VO-ST, Linder Höhe, D-51140 Köln, Germany, e-mail: [email protected] Shane R Cloude, e-mail: [email protected] Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 FEB 2007 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Polarimetric Interferometry 5a. CONTRACT NUMBER