多角度极化SAR图像中的非各向同性散射估计与消除方法研究

Estimation and Removing of Anisotropic Scattering for Multiaspect Polarimetric SAR Image

通过对不同角度子孔径相干累加,多角度观测SAR可以提供高分辨率影像及多角度散射特征。然而,现有的累加成像方法存在非各向同性散射中心混叠问题。混叠将造成极化特征参数估计无法反映实际的目标物理特征,从而难以支撑分类及变化检测应用。为了去除不同散射中心间的相互干扰并利用不同类型的信息,该文提出了一种多角度极化SAR图像中的非各向同性散射估计与消除方法。该方法给出了基于两类目标假设的最大似然比检验统计量,分析了相干斑影响以及非各向同性散射消除机理,证明了恒虚警判决函数的单调性。通过机载P波段极化SAR进行了360°观测试验,分析了非各向同性散射消除前后极化熵的变化,验证了算法的有效性并揭示出在目标特征提取方面的应用潜力。

Multiaspect Synthetic Aperture Radar （SAR） can generate high resolution images and target scattering signatures in different azimuth angles from the coherent integration of all subaperture images. However, mixed anisotropic scatters limit the application of traditional imaging theory. Anisotropic scattering may introduce errors in polarimetric parameters by decreasing the reliability of terrain classification and detection of variability. Thus a method is proposed for estimating and removing anisotropic scattering in multiaspect polarimetric SAR images. The proposed algorithm is based on the maximum likelihood and likelihood-ratio tests for the two-class case, while considering the speckle effect, the mechanism of removing the anisotropic scattering, and the monotonicity of the Constant False Alarm Rate （CFAR） detection function. We compare the polarimetric entropy before and after removing the anisotropic subapertures, and then validate the algorithm＇s potential in retrieving the target signature using a P-band quad-pol airborne SAR with circular trajectory.