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Simulation of tidal current components and oil spills spreading from Radarsat
Current Speed Model
The current velocity modeled by applying the azimuth velocity equation. The azimuth velocity component of current movements was obtained by Vx = - Dx dx v2 / Df l R (3) where dx is the pixel spacing in azimuth direction and Df is the difference between the look center frequencies of the two successive images and l is the wavelength and R is the distance between antenna and the target [3]. The current speeds modeled from RADARSAT image were related to the tidal current modeled by using M2 components from tidal table (1997). The Lagrangian method was applied with finite difference grids to simulate tidal current components from Radarsat image. These tidal current components are divided into their x and y components as: u = Ui + Vj (4) U and V are determined from surrounding grid nodes by means of Lagrangian interpolation [2]. The statistical regression model was applied in order to investigate the tidal currents components effects on oil spill pattern.  Fig - 3
Results and Discussion The composite image of texture analysis, LEE filter and Gamma filter shows that a heavy ship traffics near to Johor Barua which it may be caused oil spills (Fig. 1). The result of LEE filter shows that the oil spills curved along the coastal water of Malacca Straits (Fig. 1). It is interesting to find that the LEE filter is suitable for oil spills detection. This is because of the fact that LEE filter can reduce the noise variance beside multiplicative noise and additive noise. Table 1 shows the summaries of fractal dimension results. The sea surface is dominated by steady value of fractal dimension of 2.63 while the oil spills have a different value of fractal dimension ranged between 2.03 to 2.43. This finding is similar to study of Benelli and Garzelli, [1]. Fig. 2 shows the simulated current velocity from Radarsat image. The simulation results are in conformity that the largest current speeds are found in the largest area of oil spill width. The tidal current components U and V have a higher positive frequency (Fig. 3). This means that the strong tidal current movements was towards the northwest direction. The V components have a larger velocity than U components. The maximum V velocity is 1.34 m/s while the maximum U velocity is 0.15 m/s. It was noticed that the U and V components move in two opposite directions. The effects of tidal current components on oil spill patterns can observed from Figs. 4a and 4b. It is obvious that the V components have good effects on oil spill lengths than U components. However, U components have good effects on oil spill widths than V components. It can explain that due to the effects of V components, the oil spills moved towards the north direction. This means that the spreading of oil spills towards the west coast of Malaysia will be due to the effects of U components.  Fig - 4 It can be concluded that the fractal dimension method is good method for oil spills detections from radar data. RADARSAT data shows a good potential for detection oil spills and modelling of tidal current effects on oil spill patterns. Tidal currents have two directions on the oil spill patterns. The V components have a most effects on the oil spill lengths toward the north and the U components could be effected the spreading of the oil spills toward the west. References
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