PolSAR Ship Detection Based on Azimuth Sublook Polarimetric Covariance Matrix

Polarimetric synthetic aperture radar (PolSAR) is an important tool for marine remote sensing. In the past two decades, subaperture decomposition is considered as an alternative method to extract ship targets, especially in complex conditions where the detection based on intensity performs not well. The introduction of polarization information can enhance the detection ability of radar. The combination of sublook techniques and polarization will lead to more precise target extraction. The first methods jointly using information of polarization and sublook is the polarimetric internal Hermitian product (Pol-IHP), which nowadays has been corrected as Pol-HIP. However, it is limited by the number of sublooks and recently developed as generalized multi-sublooks correlation. In this article, a novel sublook polarimetric covariance matrix (SPCM) is established, based on which a sublook-polarimetric whitening filter (sub-PWF) is further proposed for ship detection. The SPCM represents a given pixel using a high-dimensional covariance matrix which utilizes the spectral correlation in imaging progress and the scattering characteristics of different polarization channels. The superiority of sub-PWF based on SPCM is validated via the measured single look complex PolSAR data from RadarSAT-2 and GaoFen-3. Results show this new method can improve the target to clutter ratio and reduce the clutter fluctuation. The ROC curves in both small and large scenes proves that sub-PWF can reach ideal detection performance.