Improvement of SSA Approach for Numerical Simulation of Sea Surface Scattering at High Microwave Bands

Abstract

Small slope approximation (SSA) is a widely accepted approach in sea surface electromagnetic (EM) scattering studies. Nevertheless, the spatial sample interval used for sea surface should be around or even smaller than one-eighth of the incident wavelength to ensure EM scattering calculation accuracy, which requires a huge amount of computation, creating an obstacle to scattering numerical simulation, especially for high microwave band incident waves and large sea surface scenes. In this paper, a novel realization approach for SSA is proposed to significantly decrease the computation demands and computer memory requirements in sea surface scattering simulation. First, the sea surface is decomposed into two scales, and each scale has its own spatial sample interval. Then, the inclination state of the large-scale sea surface is determined under a specific wind speed. After that, scattering calculations of a typical surface cell with a finely sampled structure are completed and saved in all possible situations. Finally, scattering results for all the cells of a concrete sea surface are extracted from the saved cell scattering data base. From the different kinds of scattering result comparisons, it is demonstrated that this novel SSA realization approach can attain almost similar scattering results to exact SSA. This approach can be broadly applied in composite scattering studies, and remote sense imaging simulation of large sea surfaces with multiple targets.

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

“…Taking into account the tilt and hydrodynamic modulations, NRCS is then defined by [53], [117] σ (x, y) = σ 0 1 + M (k) Z (k) e ikx + c.c. dk (44) where Z(k) is the 2D Fourier transform of the sea surface model Z. The complex RAR modulation transfer function (MTF) is presented as a sum M (k) = M t (k) + M h (k), where for the left looking SAR scanning geometry [47], [53] M t (k) = 4 cot θ r 1 ± sin 2 θ r ik y (45) with the plus sign related to VV and minus sign to HH polarization, and…”

“…As the TSM has gained prominence many different im-provements and additions have been introduced: simulation of multiview SAR wave synchronization data for azimuth cutoff wavelength compensation [37], polarimetric TSM [38], sea surface velocity of wind retrieval [39], improved TSM [40], [41], facet-based modification of TSM [42], application of modified TSM to breaking waves simulation [23], and finally interesting approaches which, although not directly related to TSM, use the same scale-splitting principle to generate sea surface for infrared imaging [43] and for improving SSA calculations [33], [44], [45].…”

A Volume-Surface Composite Scattering Model for Nonlinear Ocean Surface With Breaking Waves and Foam Layers Under High Wind Conditions

“…The study of the electromagnetic scattering mechanism from the sea surface is of great significance in remote sensing systems and target recognition with complex background [1]. The research on the electromagnetic scattering model of the sea surface can not only help to estimate and optimize the target recognition algorithm, but also be used to supplement experimental data [2][3][4]. The high-resolution radar characteristics of the sea surface under high wind conditions at low grazing angles (LGA) have been a point of discussions and in-depth analysis in recent years [5][6][7][8].…”

Efficient Numerical Full-Polarized Facet-Based Model for EM Scattering from Rough Sea Surface within a Wide Frequency Range

“…The electromagnetic (EM) scattering by a rough sea surface has been carefully studied for a long time [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], and many methods have been proposed. Generally, due to the electrically large size of the sea surface at microwave bands, analytical approximation methods are widely employed, such as the Kirchhoff approximation (KA), the small perturbation method (SPM) [8], the two-scale model (TSM) [6] and the small-slope approximation (SSA) [9].…”