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Simulation of Bathymetry Pattern from Polarised TOPSAR
Simulation Model
Coastal water bathymetry features are imagined on SAR images due to the surface current signature on SAR images. Simulation model of coastal bathymetry will be based on the imaging mechanisms of surface current gradients by SAR. In doing so, the Volterra series expansion was used to model surface current signature gradients by SAR. The SAR intensity image is in linear Kernal, which could detect the current movements along the range direction . The SAR image intensity derived from Fourier transform will have a linear relationship with surface current component in range direction. This can be given by Ur=(jjbvx + kyv.H)-1.1(vx,vy (2) Where is function of the action and the wave spectrum at equilibrium stage. One the current have been estimated, the water depth can be computed from the continuity equation. Power –1 indicate the inversion of the inversion of the linear Kernal of Volterra model. dh/dt+Ñ {(D+h)u}=0 (3) Where dh is the surface elevation above the mean sea level and D is the water depth. Boundary Condition The simulated water depth area is divided into square meshes of 2000 m x 2000 m and the water depths at each grid square are interpolated. This interpolated water depths data is then used to create the bottom contour map. The western boundary is the line parallel to the coastline of Kuala Terengganu started from Kuala Terengganu river towards the north which approximately 20 km. The eastern boundary is extending towards the offshore by 5 km away from the western boundary. The tidal elevation was 1 m in initial time and increased to 1.6 m. The current speed in initial time less than 0.5 m/s and higher than zero m/s Results and Discussion Figure 1 shows the C band TOPSAR data with underwater bottom topography signature. This image contains a lot of speckle noises which cannot be directly utilized. Figure 2 shows the smooth image by anisotropic diffusion filter. It is noticed that speckle noises have been reduced and the signature of underwater singularities do not broaden. This is because of the fact that anisotropic diffusion filter model preserved the mean grey level and kept the singularities in place. This result is similar to Inglada and Garello, (1999).
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