Model Order Selection in Multi-baseline Interferometric Radar Systems
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Model Order Selection in Multi-baseline Interferometric Radar Systems Fabrizio Lombardini Dipartimento di Ingegneria dell’Informazione, Universit´a di Pisa, via Diotisalvi 2, 56126 Pisa, Italy Email: [email protected]
Fulvio Gini Dipartimento di Ingegneria dell’Informazione, Universit´a di Pisa, via Diotisalvi 2, 56126 Pisa, Italy Email: [email protected] Received 18 August 2004; Revised 23 May 2005 Synthetic aperture radar interferometry (InSAR) is a powerful technique to derive three-dimensional terrain images. Interest is growing in exploiting the advanced multi-baseline mode of InSAR to solve layover effects from complex orography, which generate reception of unexpected multicomponent signals that degrade imagery of both terrain radar reflectivity and height. This work addresses a few problems related to the implementation into interferometric processing of nonlinear algorithms for estimating the number of signal components, including a system trade-off analysis. Performance of various eigenvalues-based informationtheoretic criteria (ITC) algorithms is numerically investigated under some realistic conditions. In particular, speckle effects from surface and volume scattering are taken into account as multiplicative noise in the signal model. Robustness to leakage of signal power into the noise eigenvalues and operation with a small number of looks are investigated. The issue of baseline optimization for detection is also addressed. The use of diagonally loaded ITC methods is then proposed as a tool for robust operation in the presence of speckle decorrelation. Finally, case studies of a nonuniform array are studied and recommendations for a proper combination of ITC methods and system configuration are given. Keywords and phrases: multichannel and nonlinear array signal processing, multicomponent signals, radar interferometry, synthetic aperture radar.
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INTRODUCTION
Synthetic aperture radar interferometry (InSAR) is a powerful and increasingly expanding technique to derive digital height maps of the land surface from radar images, with high spatial resolution and accuracy [1, 2]. The surface height is estimated from the phase difference between two complex SAR images, obtained by two sensors slightly separated by a cross-track baseline. The InSAR technique is finding many applications in radar remote sensing, for example, for topographic and urban mapping, geophysics, forestry, hydrology, glaciology, sighting for cell phones, flight simulators [1, 2]. Accurate measurement of radar reflectivity is useful for vegetation and snow mapping, forestry, land-use monitoring, agriculture, soil moisture determination, mineral exploration, and again for hydrology and geophysics [3]. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
However, conventional single-baseline InSAR suffers from possible layover phenomena, which show up when the imaged scene c
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