NL-SAR: A Unified Nonlocal Framework for Resolution-Preserving (Pol)(In)SAR Denoising
NL-SAR: A Unified Nonlocal Framework for Resolution-Preserving (Pol)(In)SAR Denoising
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DOI：
10.1109/tgrs.2014.2352555
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发表时间：
2015-04-01
影响因子：
8.2
通讯作者：
Jaeger, Marc
中科院分区：
文献类型：
--
作者：
Deledalle, Charles-Alban;Denis, Loic;Jaeger, Marc
斑点噪声是合成孔径雷达等相干成像系统中固有的问题。它造成强烈的强度波动，并阻碍图像分析和局部辐射、偏振或干涉特性的估计。因此，合成孔径雷达(SAR)处理链通常包括用于斑点噪声抑制的多视(即，平均)滤波器，其代价是强分辨率损失。保存点状和精细的结构和纹理需要对估计进行局部调整。非局部(NL)-指通过从小图像块之间的相似性获得数据驱动的权重来成功地适应平滑。非局部方法的推广为保持分辨率的斑点噪声抑制提供了一个灵活的框架。我们描述了一种通用的方法，即NL-SAR，它建立扩展的非局部邻域来去除幅度、极化和/或干涉SAR图像的噪声。这些邻域是基于像素相似度来定义的，所述像素相似度是通过多通道斑块比较来评估的。进行了多个非局部估计，并在局部选择最好的一个，以形成一幅保留了雷达结构和不连续性的单一恢复图像。所提出的方法是全自动的，可以处理单视和多视图像，可以有或没有干涉或极化通道。用模拟数据、机载和星载雷达图像进行的数值实验表明，该方法能有效地抑制相干斑，并保持很好的分辨率。文中给出了NL-SAR并行实现的源代码。
Speckle noise is an inherent problem in coherent imaging systems such as synthetic aperture radar. It creates strong intensity fluctuations and hampers the analysis of images and the estimation of local radiometric, polarimetric, or interferometric properties. Synthetic aperture radar (SAR) processing chains thus often include a multilooking (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. Nonlocal (NL)-means successfully adapt smoothing by deriving data-driven weights from the similarity between small image patches. The generalization of nonlocal approaches offers a flexible framework for resolution-preserving speckle reduction. We describe a general method, i.e., NL-SAR, that builds extended nonlocal neighborhoods for denoising amplitude, polarimetric, and/or interferometric SAR images. These neighborhoods are defined on the basis of pixel similarity as evaluated by multichannel comparison of patches. Several nonlocal 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 multilook 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 this paper.