Ship Wake Components: Isolation, Reconstruction, and Characteristics Analysis in Spectral, Spatial, and TerraSAR-X Image Domains

Based on a joint analysis of linear Kelvin wake kinematics and water dispersion relation, the features of several components of ship wake are identified in the spectral domain, such as the “X”-shaped Kelvin wake, the narrow “X”-shaped solitary wave packets, and the cross-shaped turbulent and near-field waves. Alternatively, these components can be separately reconstructed in spatial domain using the inverse Fourier transformation. These relations are verified through numerical simulation of the wakes of a ship moving at different speeds. This wake decomposition is now extended to wake feature analysis of real synthetic aperture radar (SAR) image. It reveals that although the images of ship wake have been modulated by SAR imaging mechanisms in various aspects, their spectral characteristics are closely analogous to that of wake surface elevation. Taking advantage of the loci and shape of the wake spectrum, the transverse wave, the divergent wave, the turbulent wave, and the solitary wave packets can be isolated from the original SAR image with full wake appearance. The reconstructed images of wake components facilitate the further estimation of the direction, speed, length, hull geometry, and propulsion system of the ship. This decomposition can also recover wake components from multiple ship wakes and provide an understanding of their roles on SAR image.