## 3 The Proposed Method
### Polarimetric Parameters Extraction  
As is known, the backscattering of the calm or low state water can be modeled as the Bragg surface scattering [30]. However, the scattering of water regions near a port or an urban area are different due to the interference of the surrounding man-made  
Figure 2: Diagram of the proposed port detection method. buildings or ships. The scattering components of the water regions near a port or an urban area are usually more complex than those of other normal water regions. As shown in Figure 3, the Pauli pseudocolor image of Zhanjiang is shown in Figure 3a, where the sampling regions are marked in red boxes. The Pauli pseudocolor images of the four sampling regions, including a calm water region, an interference water region near an urban area, an interference water region on a port, and a vegetation region, are shown in Figure 3b-e, respectively. We can observe that the color of the two interference water regions in Figure 3c,d is redder than that of the calm water. The histograms of the span of the three regions are shown in Figure 3f, where \(\text{Span}_{\text{n}}\), \(\text{Span}_{\text{i}}\), and \(\text{Span}_{\text{i}}\) denote the histogram of the calm water region, the interference water region, and the land region, respectively. Statistical results validate that the scattering power of the interference water region is much higher than that of the calm water region. The scattering power of the interference water region is less than that of the land region. In the remainder of the article, the interference water stands for water regions interfered with by buildings in an urban area or a port, the port water stands for water regions on a port, and the normal water stands for water regions opposite to the interference water. To analyze the scattering component of the port water, we obtain the Freeman-Durden three-component decomposition result of the sampled water regions in Figure 3 using (1). The histograms of normalized power \(P_{s}\)/Span, \(P_{d}\)/Span, and \(P_{v}\)/Span of the port water are shown in Figure 4a, where the three histograms are drawn in red, green, and blue, respectively. We can observe that the ratio of the \(P_{d}\) scattering power of most pixels is larger than 0.5. Statistical results validate that the scattering component of the interference water is dominated by the double-bounce scattering component. This result is mainly caused by two factors. One is the sidelobe effect of strong scattering objects. Since the scattering power of strong scattering objects is dominated by double-bounce, the scattering component of the region interfered with by the sidelobe is also dominated by double-bounce scattering. The other is the double-bounce scattering components generated by the dihedral corner reflector between the strong scattering objects and the interference  
Figure 3: The Pauli pseudocolor images and histograms of the sampled water and land regions: (**a**) The Pauli pseudocolor image of Zhanjiang, where the sampling regions are marked in red boxes; (**b**) a calm water region; (**c**) an interference water region near an urban area; (**d**) an interference water region in a port; (**e**) a vegetation land region; (**f**) the histograms of the span of the three sampling regions, where \(\text{Span}_{\text{n}}\), \(\text{Span}_{\text{i}}\), and \(\text{Span}_{\text{i}}\) denote the histogram of the calm water region, the interference water region, and the land region, respectively. water. The scattering distribution of \(P_{s}/\)Span, \(P_{d}/\)Span, and \(P_{o}/\)Span components of the three different sampled water regions and the sampled land regions is shown in Figure 4b. Figure 4b shows that not only the water regions and the land region but also the three kinds of water regions are separable. To find out the distinct scattering component of the port water, the histograms of the scattering power of the port water are fitted using a gamma distribution.