Application of Facet Scattering Model in Sar Imaging of Sea Surface Waves With Kelvin Wake

Abstract

Abstract-The principal purpose of this work is the simulation of the ship wake in Synthetic Aperture Radar (SAR) imaging based on a facet scattering model. The hydrodynamic model of the surface waves mainly considers the Kelvin wake waves and the wind driven waves. For the prediction of radar returns from the composite surface, the semi-deterministic facet scattering model (SDFSM) is proposed, which is verified to have good performance through a comparison with the experiment by SASS-II. Then, the distributions of backscattering normalized radar cross section (NRCS) of facets are investigated for both V V and HH polarizations and characteristics of the wake pattern are shown with good visibility. On the basis of these, an application of velocity bunching (VB) imaging model is presented in detail for the simulation of SAR imaging of sea surface waves with Kelvin wake. Finally, several numerical results provide states of the effects of ship speed, wind speed and the ship sailing direction on the characteristics of Kelvin wake in SAR images. Thus, this simulation may enable us to provide a theoretical basis to the detection of ship wakes.

Modeling and SAR Imaging of the Sea Surface: a Review of the State-of-the-Art with Simulations

“…As is mentioned in Section V-A, and, in various studies in the literature, the ambient amplitude of sea waves can dramatically reduce or reversely increase the visibility of vessel signatures in SAR images. On the other hand, different spectra models have been applied for SAR image simulation of ship wake [6], [58], [60], [63], [65]- [69], [71], [72]. It is important to note that the results presented here reveal a relative difference in spectra, in terms of a superposition of sea waves with ship wake and are not compared in terms of absolute SAR intensity values.…”

“…When considering superposition, it is important to select the correct wind velocity value for modeling. In many studies [5]- [8], [61], [71], [97], [127], [128], it is postulated that wind velocity (or consequently significant wave height) is one of the main factors in ship wake visualization in SAR imagery. The Kelvin wake system (divergent and transverse waves) can be best observed when the wind velocity is about 3 m/s or less, as these levels give a very calm sea surface [7].…”

Sea Surface Imaging Simulation for 3D Interferometric Imaging Radar Altimeter

“…The sea surface is sampled according to the set range and azimuth sampling unit size (2m × 2m). The backscattering coefficient of each sampling point is calculated as the mean value for all triangular elements in the corresponding sampling unit [36]. With n trihedral elements in a sampling unit, its backscattering coefficient c…”

Time-Varying Kelvin Wake Model and Microwave Velocity Observation

“…t scan (13) where d MIMO is the spacing of the adjacent transmit/receive elements whose value is 0.02 m. The unambiguous Doppler velocity and velocity resolution for the ground-based MIMO SAR can be expressed in the same form as for the following VSAR:…”

“…Microwave radar has been proven to be useful in observing the Kelvin wakes. The feature of Kelvin wakes in SAR images and the electromagnetic scattering characteristics from the Kelvin wakes are widely discussed [1][2][3][4][5][6][7][8][9][10][11][12][13]. Based on the Bragg mechanism of the sea surface, Tunaley et al [1] researched the SAR imaging of ship wakes in L-band and analyzed its validity through a comparison with the Sea SAT SAR imagery.…”