Multidimensional imaging with ERS data

Gianfranco Fornaro(1) , Fabrizio Lombardini(2) , and Francesco Serafino(1)

(1) Consiglio Nazionale delle Ricerche, via Diocleziano 328, I-80124 Napoli, Italy
(2) University of Pisa, via Caruso,14, I-56122 Pisa, Italy

Abstract

Synthetic Aperture Radar (SAR) focusing allows the generation of high-resolution 2D images of the acquired scene [1]. However, due to the three-dimensional nature of the acquired scene and to the possible penetration of the radiation below the surface, reconstructed images represent only a projection (over-position) of the ground volumetric scattering properties along a direction (elevation) orthogonal to the line of sight. SAR Interferometry is a technique that permits, by using a pair of images, reconstructing the height profile of the observed scene [1], however, it does not allow one to separate different scattering mechanisms in the elevation (height) direction. Multi-baseline SAR imaging, represents a recent advance with respect to SAR and Interferometric SAR imaging, which is receiving great interest in the last years. In particular, 3D SAR tomography allows discriminating objects along the elevation direction and thus separating different scattering mechanisms in the same azimuth-range resolution cell [2-5]. With existing satellites, multiple baselines are synthesized with successive passes (multi-pass) of the same satellite at different times, but many efforts of space agencies are dedicated to planning and design of satellite constellations, which will make it possible in the future to acquire multibaseline data nearly at same time [6]. The availability of multi-dimensional (multi-baseline and multi-temporal) data allows also implementing a Differential SAR Tomography or 4D imaging technique. More specifically, such technique permits to separate both position along elevation direction and relative deformation velocities of objects located in the same azimuth-range resolution cell [7-8]. Experiments of 3D imaging with real data have been carried out only in laboratory [2], by using airborne data [3] or on limited number of passes and few scatterers with satellite data [4]. On the other hand, existing literature does not address experiments of 4D imaging with real data neither in laboratory nor with airborne or satellite data. The work in this paper, aims to describe the results in multidimensional imaging obtained by using ERS data acquired over the area of Naples in the period 1992-2000. In particular results of 3D imaging, showing the capability of multidimensional SAR image to reconstruct scattering mechanism over complex structures, will be presented. Furthermore, first result of 4D imaging will be shown to demonstrate the potentialities related to the extension of 3D imaging to the time monitoring of ground slow moving scatterers interfering in the same resolution cell.

[1] R. Bamler, P. Hartl, “Synthetic Aperture Radar Interferometry”, Inverse Problems, vol. 14, pp. R1-R54, 1998.

[2] P. Pasquali, C. Prati, F. Rocca, M. Seymour, J. Fortuny, E. Ohlmer, A.J. Sieber, “A 3D SAR Experiment with EMSL Data,” Proc. IGARSS’95, pp.784-786, Firenze, Italy, 1995.

[3] A. Reigber, A. Moreira, “First Demonstration of Airborne SAR Tomography Using Multibaseline L-Band Data”, IEEE Trans. Geosci. Remote Sensing, vol. 38, pp. 2142-2152, Sept. 2000.

[4] Z. She, D. A. Gray, R. E. Bogner, J. Homer, and I.D. Longstaff, “Three-dimensional Spaceborne Synthetic Aperture Radar (SAR) Imaging with Multipass Processing”, Int. J. Remote Sensing, 23, 4357-4382, October 2002.

[5] G. Fornaro, F. Lombardini, F. Serafino, “Three Dimensional Multipass SAR Focusing: Experiments with Long Term Spaceborne Data”, IEEE Trans. Geosci. Remote Sens., vol. 43, pp. 702-714, April 2005.

[6] G. Krieger, A. Moreira, “Multistatic satellite formation: potentials and challenges,” Proc. IGARSS 05, Seoul, Korea.

[7] F. Lombardini, ‘Differential Tomography: a New Framework for SAR Interferometry’, Proc. IGARSS’03, Toulose, France, July 2003.

[8] F. Serafino, F. Soldovieri, F. Lombardini, G. Fornaro, “Singular Value Decomposition applied to 4D SAR Imaging”, Proc. IGARSS 05, Seoul, Korea.

 

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