Performance Evaluation of Polarimetric SAR Interferometry in Urban Scenarios: Analysis of Simulated Images and Cross-correlation with Real Data.
Gerard Margarit(1), Jordi J. Mallorqui(2) and Carlos Lopez-Martinez(2)
(1) GMV A&D, C Balmes, 268-270, 5th floor, E-08006, Barcelona, Spain
(2) Universitat Politècnica de Catalunya (UPC), D3, Campus Nord, C Jordi Girona, 1-3, E-08034, Barcelona, Spain
The study of urban environment with SAR is devoting increased interested because the new missions are providing improved performance, especially in terms of image resolution. This would allow to complement the knowledge about urban dispersion and the relations that may exist between specific urban structures, and the measured RCS and elemental scattering mechanisms. But by now, this information is strongly limited and not supported by a theoretical framework that gathers formulation, tests and/or simulation analysis. Instead, it is being empirically updated once new images become processed and interpreted under a physical point of view.
Besides the lack of precise ground-truth, one of the main reasons for the limited knowledge about urban Electromagnetic (EM) dispersion is the complexity of urban scenarios. Normally, they account a high number of interfering elements with random locations and orientations, which make quite difficult to theoretically analyze EM backscattering. A common solution to this drawback has normally laid on the usage of geometry simplifications in terms of elemental canonical shapes. Despite it makes EM formulae affordable, it drops drastically accuracy because the finite combination of canonical reflections can not model the unpredictable responses caused by the small scale details (and by the lack of symmetry). In this framework, the usage of simulation tools appears to be a feasible alternative because allow to work with high flexibility within realistic scenes. Example is the SAR simulator, GRECOSAR , developed at UPC’s Remote Sensing Laboratory and able to deal with extremely complex scenarios. As stated in previous ship studies , this tool has proved to provide high accuracy on estimating the scattering information in the four polarimetric channels with non-demanding computational load.
This paper proposes the usage of GRECOSAR for studying the SAR response of urban scenarios. RADARSAT-2 and TerraSAR will be used as reference sensors for the study. Different targets and scenarios will be considered in order to evaluate how urban-like targets scatter and which information can be extracted from the polarimetric and interferometric measurements. In this sense, the main application foreseen is differential interferometry, DInSAR, with the added value of high resolution imagery. The techniques initially proposed for vessel classification  will be applied to urban scenarios to help distinguish within the same resolution cell different scattering mechanisms placed at different heights. There, Polarimetry is the key element as provides redundancy of information and the possibility to better identify certain structures, which may be helpful for subsidence.
1. G. Margarit, J. J. Mallorqui, J. M. Rius, and J. Sanz-Marcos, “On the usage of GRECOSAR, an orbital polarimetric SAR simulator of complex targets, for vessel classification studies,” IEEE Trans. Geosci. Remote Sensing, vol. 44, no. 12, pp. 3517–3526, Dec. 2006.
2. G. Margarit, J. J. Mallorqui, and X. Fabregas, “Single-pass polarimetric SAR Interferometry for Vessel Classification,” IEEE Trans. Geosci. Remote Sensing, EUSAR Special Issue, vol. 45, no. 11, pp. 3494–3502, Nov. 2007.