NL-SAR: a unified Non-Local framework for resolution-preserving PolInSAR denoisingReport as inadecuate

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1 CNRS - Centre National de la Recherche Scientifique 2 IMB - Institut de Mathématiques de Bordeaux 3 LHC - Laboratoire Hubert Curien Saint Etienne 4 Télécom ParisTech 5 LTCI - Laboratoire Traitement et Communication de l-Information 6 D.L.R. - Microwaves and Radar Institute

Abstract : Speckle noise is an inherent problem in coherent imaging systems like synthetic aperture radar. It creates strong intensity fluctuations and hampers the analysis of images and the estimation of local radiometric, polarimetric or interferometric properties. SAR processing chains thus often include a multi-looking i.e., averaging filter for speckle reduction, at the expense of a strong resolution loss. Preservation of point-like and fine structures and textures requires to adapt locally the estimation. Non-local means successfully adapt smoothing by deriving data-driven weights from the similarity between small image patches. The generalization of non-local approaches offers a flexible framework for resolution-preserving speckle reduction. We describe a general method, NL-SAR, that builds extended non-local neighborhoods for denoising amplitude, polarimetric and-or interferometric SAR images. These neighborhoods are defined on the basis of pixel similarity as evaluated by multi-channel comparison of patches. Several non-local estimations are performed and the best one is locally selected to form a single restored image with good preservation of radar structures and discontinuities. The proposed method is fully automatic and handles single and multi-look images, with or without interferometric or polarimetric channels. Efficient speckle reduction with very good resolution preservation is demonstrated both on numerical experiments using simulated data, airborne and spaceborne radar images. The source code of a parallel implementation of NL-SAR is released with the paper.

Keywords : Polarimetry Estimation Non-local means Synthetic Aperture Radar SAR Interferometry

Author: Charles-Alban Deledalle - Loïc Denis - Florence Tupin - Andreas Reigber - Marc Jäger -



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