HD-02: SAR Interferometry and Multidimensional Tomography for Advanced Imaging and Monitoring
Fabrizio Lombardini, Gianfranco Fornaro
Abstract:
Synthetic aperture radar (SAR) Interferometry allowing generation of topographic maps, accurate localization of ground scatterers, and monitoring of possible displacements to a mm/year order, is one of the techniques that have most pushed the applications of SAR to a wide range of scientific, institutional and commercial areas, and it has provided significant returns in particular in terms of improvements in the risk monitoring.
SAR images relative to a same scene and suitable for interferometric processing are today available for most of the Earth, and their number is exponentially growing. Archives associated to SAR spaceborne sensors are filled by data collected with time and observation angle diversity (multipass-multibaseline data); moreover, current system trends in the SAR field involve clusters of cooperative formation-flying satellites with capability of multiple simultaneous acquisitions (bistatic and multistatic tandem SAR systems), airborne systems with multibaseline acquisition capability in a single pass are also available, and unmanned air vehicles with capability of differential monitoring of rapid phenomena are being experimented. In parallel, developments are underway of processing techniques, evolutions of the powerful SAR Interferometry, aimed at fully exploiting the information lying in such huge amount of multipass-multibaseline data, to produce new and/or extended measuring functionalities.
The tutorial will cover aspects spanning from basics of Interferometry and of multipass/multibaseline Differential interferometric techniques for accurate deformation measurement, that have dramatically accelerated the SAR application to natural hazards, to the recent developments, framed in the context of Tomographic SAR Imaging, which play an important role in the analysis of complex scenarios such as urban and forest areas. In particular processing methods will be treated that, in the emerged framework of coherent SAR data combination at the complex (phase and amplitude) value level, differently from phase-only Interferometry, allow improved or novel imaging and differential monitoring capabilities, in terms of accuracy and unambiguous interpretation of the measurements.
After an introduction on the basic concepts of SAR Interferometry, most important techniques will be presented and discussed with respect to the specific application. These techniques are: 1) the Small Baseline Subset (SBAS) approach for monitoring deformation of the Earth surface at coarse scale of large areas; 2) Persistent Scatterers Interferometry (PSI) for monitoring deformations of man-made structures; 3) 3D Tomography to allow profiling of the scattering distribution also along the elevation direction for unambiguous extraction of physical and geometrical parameters in geophysical structures with vertical stratification sensed by low frequency SARs, as well as for separating scatterers in layover over vertical man-made structures with high frequency SAR sensors; 4) Multipass "4D" (3D+velocity) "Differential Tomography" of multiple layover scatterers with slow deformation motions, a recent and very promising multidimensional imaging mode crossing the bridge between Differential Interferometry and Multibaseline Tomography.
Basic concepts, signal models and processing methods of Interferometry and of 3D/4D Tomographic SAR Imaging will be described, the latters Fourier based, and of super-resolution kind (adaptive, a priori information-based, and model-based). A number of experimental results obtained with real data, multibaseline single-pass and multipass airborne, and multipass spaceborne, in X-, C-, L-, and P-band (AER-II, E-SAR, ERS-1/2, ENVISAT, RADARSAT-2, COSMO-SkyMed, TerraSAR-X), over infrastructure, urban, and forest areas, will be presented to show the important applications of SAR Interferometry to real cases, also in conjunction with emergency situations, as well as to demonstrate the improved performance from the advanced 3D/4D Tomography framework. New trends in the area will be also shown, including comparison with the recent compressive sensing Tomography, and the ("5D") concepts of 3D Tomography robust to temporal decorrelation through higher-dimensional processing and Differential Tomography of non-uniform deformation motions.
A general basic knowledge of radar and standard signal processing is useful for fruitfully attending the tutorial.
Biography:
Fabrizio Lombardini (M'93-SM'03) received the Italian Laurea degree (with honors) in electronic engineering and the PhD degree in telecommunication engineering from the University of Pisa, Italy, in 1993 and 1997, respectively. He was then granted by the EU a Marie Curie Fellowship of the Training and Mobility of Researchers (TMR) Program, which he spent as Postdoctoral Researcher at the Department of Electronic and Electrical Engineering of University College London, U.K., from 1998 to 1999. Then, he joined the Department of Information Engineering of University of Pisa, where he currently holds the position of Assistant Professor. Since 2011 he is also Consultant at the National Laboratory of Radar and Surveillance Systems of the Italian National Interuniversity Consortium for Telecommunications (CNIT-RaSS). He has given lectures at universities and institutions in Italy and abroad, has organized and chaired 16 special sessions on Synthetic Aperture Radar (SAR) multibaseline/multichannel interferometry, coherent data combination, and three-/multi-dimensional techniques at international conferences (including IEEE IGARSS 2005, IGARSS 2007, IGARSS 2008, IGARSS 2009, IGARSS 2010, IGARSS 2012, and IGARSS 2013), has served as Editor of the EURASIP Journal of Applied Signal Processing (JASP) special issue on "Advances in Interferometric SAR Processing", and has been lecturer or co-lecturer of 6 tutorials on SAR tomography and multidimensional SAR imaging at EUSAR 2008, IEEE RadarCon09, IEEE IGARSS 2010, IGARSS 2011, IGARSS 2012, and IGARSS 2013. Dr. Lombardini's general interests are in the areas of statistical signal processing, estimation and detection, super-resolution spectral analysis, array processing, and performance bounds evaluation, with application to radar systems and SAR environmental remote sensing. He has authored or co-authored more than 130 papers (peer-review journals and proceedings of international conferences) on these subjects. In particular, his research interests include multisensor data fusion and radar detection in non-Gaussian clutter, multibaseline and multifrequency interferometric SAR algorithms and systems, both cross- and along-track, 3D SAR tomography, and differential SAR interferometry. He has originated the new interferometric mode of differential SAR tomography (4D SAR imaging), and has recently engaged research on coherent localization in radio frequency identification (RFID) systems.
Gianfranco Fornaro (M'06-SM'08) received the M.S. degree (summa cum laude) in electronic engineering and the Ph.D. degree from the University of Naples "Federico II" in 1992 and 1997, respectively. Since 1993 he has been with Institute for Electromagnetic Sensing of the Environment (IREA) of the Italian National Research Council, Naples, where he is currently a Senior Researcher working in the area of Synthetic Aperture Radar (SAR) focusing, SAR interferometry and SAR tomography. He has been Adjunct Professor in the area of telecommunications in several Universities, currently at the University of Naples "Parthenope". Dr. Fornaro has been visiting scientist at the Politecnico of Milano and at the German Aerospace Establishment (DLR), also within the Italy-Germany cooperation during the SIR-C/X-SAR mission. He has been United Nation consultant at the Istituto Tecnologico de Aeronautica (ITA) in Sao Jose' dos Campos (Brazil) and at RESTEC (Tokyo). Since 2010 Dr. Fornaro has been lecturer at the International radar/SAR Summer School of the Fraunhofer Institute; he has been also convener and chairman of sessions dedicated to SAR processing and SAR interferometry in several international conferences. He was tutorial lecturer at EUSAR 2008, IGARSS 2010, EUSAR 2012, IGARSS 2012, has authored more than a hundred of papers (peer-review journals and proceedings of international conferences); in 2005 served as Editor of the "Advances in Interferometric SAR processing" special issue of the EURASIP Journal on Applied Signal Processing (JASP), and is currently Associate Editor of the IEEE Geoscience and Remote Sensing Letters. He received the Mountbatten Premium by the Institution of Electrical Engineers (IEE) in 1997, the IEEE Geoscience and Remote Sensing Letters 2011 Best Paper Award and the Mention for Best 2011 Reviewer for the IEEE Transactions on Geoscience and Remote Sensing journal.