Theory and PALSAR Observations of the PolInSAR pi/4 mode
Marco Lavalle(1), Domenico Solimini(1), Eric Pottier(2) and Yves-Louis Desnos(3)
(1) University Tor Vergata, Via del Politecnico, 1, 00133 Rome, Italy
(2) University of Rennes 1, 263 avenue du Général Leclerc, 35042 Rennes Cedex, France
(3) ESA, Via Enrico Fermi, 00144 Frascati, Italy
Polarimetric SAR interferometry (PolInSAR) has opened the path to promising applications, especially in the field of forest remote sensing, such as tree height estimation and multilayer topographic information retrieval. However, full polarimetry (FP) implies severe system constraints to cope with data downloading rate, size of the processed swath and power consuming. To overcome these limiting factors, a new approach for SAR polarimetry, called compact polarimetry (CP), has been proposed. In the CP architecture, the SAR transmits either a circular polarized wave or a linear polarized one oriented at 45 degrees (pi/4 mode), and receives at horizontal and vertical polarization. A theoretical formulation of CP, as well as FP reconstruction algorithms and their performance on PolSAR classification have been presented .
We address the compact PolInSAR (C-PolInSAR) formulation and present a FP reconstruction algorithm of the PolInSAR covariance matrix . The reconstruction of the full PolInSAR (F-PolInSAR) covariance matrix is based on the symmetry properties of some natural media. By assuming rotation symmetry or reflection symmetry plus an additional constraint, some PolInSAR characteristics of the vegetation result preserved.
In this contribution we first show the ALOS-PALSAR observations of the PolInSAR coherence over vegetated area and how the decorelation sources contributes to the shape of the region. Secondly, we simulate the pi/4 mode using full PolSAR data and show the performance of interferometric CP. Our analysis uses both a coherent PolInSAR simulator , that generates a fully polarimetric dataset of different forest scenarios, and real PALSAR data acquired by ALOS-PALSAR sensor at L-band over forested area. The comparison between C-PolInSAR and F-PolInSAR is based on the interferometric degree of coherence in the complex plane (coherence region) and the forest height retrieval algorithm. The comparison shows a general good agreement between the two configurations.
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 M. Lavalle, D. Solimini, E. Pottier, and Y.-L. Desnos, “Investigation of Compact Polarimetry in SAR Interferometry,” EUSAR 2008, Proceedings of, Friedrichshafen, Germany, 2-5 June 2008.
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