An entropy-based approach to wake echo analysis [ship wake radar detection]

This paper addresses the problem of ship wake detection and analysis at low grazing angles using eigenvalue analysis of the covariance matrix. Polarimetric measurements of the wake produced by a pilot boat operating in Port Phillip Bay were obtained using the Defence Science and Technology Organisation's (DSTO) high resolution radar system. By employing a polarimetric decomposition on the covariance matrix data, the polarimetric entropy, scattering alpha and anisotropy plots were obtained. Wake and clutter regions were then identified using suitable thresholds. These results were compared with previous results obtained using analysis of the S matrix data and the distribution of cross-polar null states and showed good agreement. The ratio of the maximum and minimum eigenvalues of the covariance matrix was also determined as an upper bound on the processing gain that might be achieved by exploiting the polarization domain.