FD-1: SAR Imaging, Polarimetry, Interferometry and Tomography

Presented by: Francisco Lopez-Dekker, Michael Eineder, Eric Pottier, Andreas Reigber
1,2,4 German Aerospace Center (DLR), Oberpfaffenhofen, Germany
3 Universite de Rennes 1, France

SAR Interferometry (InSAR) has become a robust and well established technique for mapping the 3D-shape of the Earth's surface. But also its changes, e.g. due to earthquakes, can be monitored with millimeter accuracy. A 20 years history of ERS-1/2 data is available now to be exploited, continued by data from other satellites such as ENVISAT/ASAR or high resolution data from TerraSAR-X or single pass InSAR data from SRTM and TanDEM-X. The tutorial introduces the concept of SAR interferometry and explains the most prominent applications such as DEM generation, land subsidence mapping and along track interferometry (ATI). The imaging configurations and their geometric sensitivities are then explained in more detail. A larger part of the tutorial covers the phase error statistics and the major error sources such as temporal and geometric decorrelation and atmospheric propagation delays. Finally, the typical InSAR data processing sequence is explained step by step. Advanced techniques such as Persistent Scatterer Interferometry (PSI) are shortly introduced. The tutorial is accompanied by examples from the most important space-borne interferometry missions including SRTM and TanDEM-X.

SAR Polarimetry (PolSAR) represents today a very active area of research in Radar Remote Sensing, and it becomes important to train and prepare the future generation to this very important topic. The aim of this tutorial is to provide a substantial and balanced introduction to the basic theory, scattering concepts, systems and advanced concepts, and applications typical to radar polarimetric remote sensing. This tutorial on SAR polarimetry touches several subjects: basic theory, scattering modeling, data representations, target decompositions, speckle filtering, terrain and land-use classification, man-made target analysis, etc. The lecture will be illustrated by ALOS-PALSAR, RadarSat2 and TerraSAR-X polarimetric SAR images. The connection to polarimetric SAR interferometry will be also briefly reviewed. The lecture is intended to scientists, engineers and students engaged in the fields of Radar Remote Sensing and interested in Polarimetric SAR image analysis and applications. Some background in SAR processing techniques and microwave scattering would be an advantage and familiarity in matrix algebra is required.

SAR Tomography: In SAR interferometry, two or more SAR acquisitions are combined to generate a high-precision digital surface model. Even though SAR interferometry is often considered to be 3D-imaging, in practice only the variations of the surface's height are measured (2.5-D imaging); any penetration of the microwaves into the target cannot be treated correctly. SAR tomography is the extension of such conventional two-dimensional SAR imaging to fully support three dimensions. SAR tomography aims to achieve a real 3D SAR image, in which semi-transparent targets, like for example forests, reveal their inner structure with great detail. Usually, this is achieved by the formation of an additional synthetic aperture in elevation direction by a coherent combination of several SAR images, acquired under a particular multi-baseline geometry.

This greatly extends the potential of SAR, particularly for the analysis of volumetric targets, like for example forested and urban areas. This tutorial introduces into the basic concepts of SAR tomography, the different possible imaging geometries, various signal models and processing techniques of coherent tomographic SAR data combination. This includes classical Fourier-based approaches, modern super-resolution techniques in a spatial spectral estimation framework as well as recently developed compressive sensing techniques for SAR tomography. Last but not least, recent extensions of SAR tomography to support polarimetric imaging and techniques to minimise the required number of tracks will be addressed. A number of experimental results obtained with real airborne data will be presented and discussed to show current and potential future achievements of this emerging technique.


Francisco (Paco) López-Dekker (S'98-M'03) was born in Nijmegen, The Netherlands, in 1972. He received the Ingeniero degree in telecommunication engineering from the Universitat Politècnica de Catalunya (UPC), Barcelona, Spain, in 1997, the M.S. degree in electrical and computer engineering from the University of California, Irvine, in 1998, under the Balsells Fellowships, and the Ph.D. degree from the University of Massachusetts, Amherst, in 2003, for his research on clear-air imaging radar systems to study the atmospheric boundary layer. During 2003 he worked as a research scientist at Starlab, where he focused on the development of GNSS-R sensors. From 2004 to 2006, he was a Visiting Professor with the Telecommunications and Systems Engineering Department, Universitat Autonoma de Barcelona. In March 2006, he joined the Remote Sensing Laboratory, UPC, where he conducted research on bistatic synthetic aperture radar (SAR) under a five-year Ramon y Cajal Grant. At the university, he taught courses on signals and systems, signal processing, communications systems and radiation, and guided waves. Since November 2009, he leads the SAR Missions Group at the Microwaves and Radar Institute, German Aerospace Center, Oberpfaffenhofen, Germany. His current research focuses on the study of future SAR missions and novel mission concepts

Michael Eineder has been with the German Aerospace Center (DLR), Wessling, Germany, since 1990, where he is currently heading the SAR Signal Processing Department of the Remote Sensing Technology Institute. DLR's Remote Sensing Technology Institute works closely together with the Lehrstuhl für Methodik der Fernerkundung of the Technische Universität München. Dr. Eineder has worked on a series of international synthetic aperture radar missions, including SIR-C/X-SAR, SRTM/X-SAR in cooperation with NASA, ERS-1/2 and ENVISAT/ASAR (ESA), and TerraSAR-X and TanDEM-X (Germany). His responsibilities encompass the development of SAR and InSAR algorithms and whole processing systems for current and future radar missions. His latest research topics include very high accuracy geometric calibration techniques for SAR and InSAR. Dr. Eineder is currently a part-time lecturer for remote sensing with the Technische Universität München (TUM). He is also leading several joint research projects between DLR and TUM.

Eric Pottier received the MSc and Ph.D. in signal processing and telecommunication from the University of Rennes 1, respectively in 1987 and 1990, and the Habilitation from the University of Nantes in 1998. Since 1999, he has been a Full Professor at the University of Rennes 1, France, where he is currently the Director of the Institute of Electronics and Telecommunications of Rennes (I.E.T.R - CNRS UMR 6164. His current activities of research and education are centered in the topics of analog electronics, microwave theory and radar imaging with emphasis in radar polarimetry. His research covers a wide spectrum of areas from radar image processing (SAR, ISAR), polarimetric scattering modeling, supervised/unsupervised polarimetric segmentation and classification to fundamentals and basic theory of polarimetry.

He has published 9 chapters in books, more than 50 papers in refereed journals and presented more than 340 papers during International Conferences, Symposiums and Workshops. He has presented advances courses and seminars on Radar Polarimetry to a wide range of organizations and events. He was presented the Best Paper Award at the Third European Conference on Synthetic Aperture Radar (EUSAR2000) and received the 2007 IEEE GRS-S Letters Prize Paper Award. In 2009 he has published a book co-authored with Dr. Jong-Sen Lee: "Polarimetric Radar Imaging: From basics to applications", CRC Press, Taylor & Francis editor, 397 pages, January. 2009, ISBN: 978-1-4200-5497-2.

He is a recipient of the 2007 IEEE GRS-S Education Award "In recognition of his significant educational contributions to Geoscience and Remote Sensing" and in 2011 has been elevated to IEEE Fellow with the accompanying citation: "for contributions to polarimetric Synthetic Aperture Radar"

Andreas Reigber received the diploma degree in physics from the University of Constance, Germany, in 1997, the PhD degree from the University of Stuttgart, Germany, in 2001, and the Habilitation from the Berlin University of Technology, Germany, in 2008. From 1996 to 2000, he has been with the Microwave and Radar Institute of the German Aerospace Center (DLR), Oberpfaffenhofen, Germany, working in the field of polarimetric SAR tomography. In 2001, he joined the Antenna, Radar and Telecom laboratories of the University of Rennes 1, Rennes, France, for a postdoc on radar polarimetry and polarimetric interferometry. From 2002 to 2007, he has been research associate at the Computer Vision and Remote Sensing laboratories of the Berlin University of Technology, Germany. Since 2008 he is back at the DLR Microwave and Radar Institute, where he is now head of the SAR technology department and directing the airborne SAR activities of the institute. In parallel, he is lecturer for remote sensing at the Berlin University of Technology. Dr. Reigber has received several Prize Paper Awards, among them the IEEE TGRS Best Paper Award in 2001 for a work on polarimetric SAR tomography. His current main research interests are the various aspects of multi-modal SAR, like SAR interferometry, SAR polarimetry, SAR tomography and time-frequency analyses, but also the application of computer vision and machine learning approaches in remote sensing.