全极化SAR图像中溢油极化特征研究

相比于单极化SAR图像，全极化SAR图像不仅能体现海面目标的几何特征、后向散射特征，还能体现目标的极化特征。因此，在溢油检测方面，极化SAR更具优势。特征提取作为溢油检测的关键步骤，直接影响到溢油检测的精度。在本文中，我们分析了全极化SAR图像中海面溢油的极化特征，如极化散射熵、平均散射角等。并提出了新的极化特征P，该特征参数能够反映海面目标电磁散射过程中布拉格散射机制和镜面散射机制的比例。为了研究极化特征溢油检测的能力，本文基于SIR-C/X-SAR和Radarsat-2全极化SAR图像开展了相关实验，并对比分析了溢油的多种极化特征。实验结果显示，在中低风速情况下，C波段溢油探测效果优于L波段；本文提出的极化特征P对海面散射机制敏感；基准高度和特征参数P在C波段比其他极化特征更适于溢油检测。

The polarimetric features of oil spills in full polarimetric synthetic aperture radar images

Compared with single-polarized synthetic aperture radar (SAR) images, full polarimetric SAR images contain not only geometrical and backward scattering characteristics, but also the polarization features of the scattering targets. Therefore, the polarimetric SAR has more advantages for oil spill detection on the sea surface. As a crucial step in the oil spill detection, a feature extraction directly influences the accuracy of oil spill discrimination. The polarimetric features of sea oil spills, such as polarimetric entropy, average scatter angle, in the full polarimetric SAR images are analyzed firstly. And a new polarimetric parameter P which reflects the proportion between Bragg and specular scattering signals is proposed. In order to investigate the capability of the polarimetric features for observing an oil spill, systematic comparisons and analyses of the multipolarization features are provided on the basis of the full polarimetric SAR images acquired by SIR-C/X-SAR and Radarsat-2. The experiment results show that in C-band SAR images the oil spills can be detected more easily than in L-band SAR images under low to moderate wind speed conditions. Moreover, it also finds that the new polarimetric parameter is sensitive to the sea surface scattering mechanisms. And the experiment results demonstrate that the new polarimetric parameter and pedestal height perform better than other polarimetric parameters for the oil spill detection in the C-band SAR images.