%NVUEDELOBTENTIONDU %0$503"5%&-6/*7&34*5² %&506-064& $ÏLIVRÏPAR Institut National Polytechnique de Toulouse (INP Toulouse) $ISCIPLINEOUSPÏCIALITÏ Signal, Image, Acoustique et Optimisation (SIAO) 0RÏSENTÏEETSOUTENUEPAR Reza Shirvany le : 30 octobre 2012 4ITRE Estimation of the Degree of Polarization in Polarimetric SAR Imagery: Principles and Applications %COLEDOCTORALE Mathématiques Informatique Télécommunications (MITT) 5NITÏDERECHERCHE Institut de Recherche en Informatique de Toulouse (IRIT) MEMBRESDUJURY: Prof. Christine Fernandez-Maloigne, Université de Poitiers, présidente Prof. Gregoire Mercier, Telecom Bretagne, rapporteur Prof. Yannick Berthoumieu, IMS Bordeaux, rapporteur Prof. Jean-Yves Tourneret, INPT-ENSEEIHT, directeur de thèse Prof. Marie Chabert, INPT-ENSEEIHT , co-directeur de thèse Institut National Polytechnique de Toulouse University of Toulouse ESTIMATIONOFTHEDEGREEOFPOLARIZATIONIN POLARIMETRICSARIMAGERY:PRINCIPLES & APPLICATIONS reza shirvany Dissertation submitted to the University of Toulouse for the degree of Doctor of Philosophy . Jury Prof. Christine Fernandez-Maloigne; Université de Poitiers; president Prof. Gregoire Mercier; Telecom Bretagne; rapporteur Prof. Yannick Berthoumieu; IMS Bordeaux; rapporteur Prof. Jean-Yves Tourneret; INPT-ENSEEIHT; advisor Prof. Marie Chabert; INPT-ENSEEIHT; co-advisor – 2012 – Copyright © 2012 by R. Shirvany {[email protected]} All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilized in any form without the prior permission of the author. To My Parents ABSTRACT olarimetric Synthetic Aperture Radar (SAR) systems have become highly fruitful thanks to their wide area coverage and P day and night all-weather capabilities. Several polarimetric SARs have been flown over the last few decades with a variety of polarimetric SAR imaging modes; traditional ones are linear single- and dual-pol modes. More sophisticated ones are full-pol modes. Other alternative modes, such as hybrid and compact dual-pol, have also been recently proposed for future SAR missions. The discussion is vivid across the remote sensing society about both the utility of such alternative modes, and also the trade-off between dual and full polarimetry. This thesis contributes to that discussion by analyzing and comparing different polarimetric SAR modes in a variety of geoscience applications, with a particular focus on maritime monitoring and surveillance. For our comparisons, we make use of a fundamental, physically related discriminator called the Degree of Polarization (DoP). This scalar parameter has been recognized as one of the most important parameters characterizing a partially polarized electromagnetic wave. Based on a detailed statistical analysis of polari- metric SAR images, we propose efficient estimators of the DoP for both coherent and in-coherent SAR systems. We extend the DoP concept to different hybrid and compact SAR modes and compare the achieved performance with different full-pol methods. We perform a detailed study of vessel detection and oil-spill recog- nition, based on linear and hybrid/compact dual-pol DoP, using recent data from the Deepwater Horizon oil-spill, acquired by the National Aeronautics and Space Administration (NASA)/Jet Propul- sion Laboratory (JPL) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). Extensive experiments are also performed over vari- ous terrain types, such as urban, vegetation, and ocean, using the data acquired by the Canadian RADARSAT-2 and the NASA/JPL Airborne SAR (AirSAR) system. vii RÉSUMÉ es radars à synthèse d'ouverture (RSO) polarimétriques sont devenus incontournables dans le domaine de la télédétec- L tion, grâce à leur zone de couverture étendue, ainsi que leur capacité à acquérir des données dans n'importe quelles conditions atmosphériques de jour comme de nuit. Au cours des trois dernières décennies, plusieurs RSO polarimétriques ont été utilisés portant une variété de modes d'imagerie, tels que la polarisation unique, la polari- sation double et également des modes dits pleinement polarimétriques. Grâce aux recherches récentes, d'autres modes alternatifs, tels que la polarisation hybride et compacte, ont été proposés pour les futures missions RSOs. Toutefois, un débat anime la communauté de la télédétection quant à l'utilité des modes alternatifs et quant au compromis entre la po- larimétrie double et la polarimétrie totale. Cette thèse contribue à ce débat en analysant et comparant ces différents modes d'imagerie RSO dans une variété d'applications, avec un accent particulier sur la surveillance maritime (la détection des navires et de marées noires). Pour nos comparaisons, nous considérons un paramètre fondamen- tal, appelé le degré de polarisation (DoP). Ce paramètre scalaire a été reconnu comme l'un des paramètres les plus pertinents pour carac- tériser les ondes électromagnétiques partiellement polarisées. A l'aide d'une analyse statistique détaillée sur les images polarimétriques RSO, nous proposons des estimateurs efficaces du DoP pour les systèmes d'imagerie cohérente et incohérente. Ainsi, nous étendons la notion de DoP aux différents modes d'imagerie polarimétrique hybride et compacte. Cette étude comparative réalisée dans différents contextes d'application dégage des propriétés permettant de guider le choix parmi les différents modes polarimétriques. Les expériences sont effectuées sur les données polarimétriques provenant du satellite Canadian RADARSAT-2 et le RSO aéroporté Améri- cain AirSAR, couvrant divers types de terrains tels que l'urbain, la végétation et l'océan. Par ailleurs nous réalisons une étude détaillée sur les potentiels du DoP pour la détection et la reconnaissance des marées noires basée sur les acquisitions récentes d'UAVSAR, couvrant la catastrophe de Deepwater Horizon dans le golfe du Mexique. ix ACKNOWLEDGMENTS La reconnaissance est la mémoire du cœur. Gratitude is the memory of the heart. —Jean-Baptiste Massieu, 1743–1818 would like to express my gratitude to the many people who supported and helped me during my Ph.D. studies, making this I time a period I will always cherish. My special thanks go to my advisor and co-adviser, Jean-Yves Tourneret and Marie Chabert, who provided me with an exciting working en- vironment, many opportunities to develop new ideas, and liberty in research, discussion and expression. I would like to thank Florent Chatelain, Nicolas Dobigeon, and Michele Galletti for productive com- ments, emails, and discussions. Special thanks also to the members of the jury who accepted this task with enthusiasm. I am, of course, indebted to professors, colleagues, and members of the University of Toulouse. I especially thank Corinne Mailhes, Marie- Laure Boucheret, Nathalie Thomas, Martial Coulon, Jérôme Severini, and the future doctors, Cécile Bazot and Sokchenda Sreng. I am also thankful to Majid Ahmadpanah, and Michel Doisy for their support and presence. A special thought goes to Henri Bauer with whom I shared the passion for photography and philosophized about life. At this point, I would like to thank my lovely parents, family, and friends for their patience, support, and everlasting fun. This was very important to me. A special thought goes to Yazdan for his helpful advices. Thanks to those, mostly far away, yet very present; Stephen, Kian, Sophia, and Liesa. I acknowledge the financial support of the French Ministry of Higher Education and Research, which made this work possible. I also acknowledge the following organizations; NASA/Jet Propulsion Laboratory (JPL), NASA/Goddard Space Flight Center (GSFC), Alaska Satellite Facility (ASF), National Oceanic and Atmospheric Administra- tion (NOAA), European Space Agency (ESA), and MacDonald, Dettwiler and Associates Ltd. (MDA). xi CONTENTS introduction 1 Chapter Review . 3 Publications . 7 1 9 Chapter 1 Overview 9 1.1 Airborne and Space-Borne Polarimetric SAR systems . 9 1.1.1 Airborne Polarimetric SARs . 10 AirSAR . 10 UAVSAR . 10 1.1.2 Space-Borne Polarimetric SARs . 10 SIR-C/X-SAR . 10 ENVISAT ASAR . 10 ALOS-PALSAR . 11 RADARSAT-2 ................... 11 TerraSAR-X . 11 Sentinel-1 ..................... 12 RCM . 12 1.2 Polarization Characteristics . 12 Jones Vector . 12 Polarimetric Covariance Matrix . 13 Stokes Vector . 13 Degree of Polarization . 14 Degree of Depolarization . 15 Degree of Polarization Uniformity . 15 Degree of Linear Polarization . 15 Degree of Circular Polarization . 15 Circular Polarization Ratio . 15 Linear Polarization Ratio . 15 Modified Stokes Vector . 16 Sinclair Matrix . 16 Scattering Vector . 16 Pauli RGB . 16 Scattering Reciprocity . 17 Barakat Full-Pol DoP . 17 1.3 Speckle Noise . 17 1.4 Theoretical Probability Distributions . 18 1.4.1 Multivariate Complex Gaussian Distribution . 18 1.4.2 Multivariate Complex Wishart Distribution . 18 1.4.3 Multivariate Gamma Distribution . 19 2 21 xiii xiv contents Chapter 2 Polarimetric SAR Imaging Modes & Study Sites 21 2.1 Classical Imaging Modes . 21 Single-Pol . 22 Dual-Pol . 22 Full-Pol . 22 2.2 Hybrid & Compact Polarimetry . 23 2.3 Data and Study Sites . 25 RADARSAT-2 San Francisco . 25 RADARSAT-2 Vancouver . 25 AirSAR San Francisco . 25 AirSAR Flevoland . 26 UAVSAR DWH . 26 3 33 Chapter 3 Statistical Analysis,Theoretical Modeling, and DoPEstimation in Dual-Pol SAR 33 3.1 Statistical Analysis of Multilook Polarimetric SAR Imagery 33 3.2 Marginal Distribution of Two Multi-look Intensity Images 36 3.3 DoP Estimation . 36 3.3.1 Coherent Dual-Pol SAR . 36 3.3.1.1 Maximum Likelihood Estimators