## 4 Experimental Results and Analysis
### Performance Comparison with Jetty Scanning Method  
In the fifth experiment, the proposed method was compared with the port detection method based on jetty scanning [7; 8], where the water extraction result detected by the thresholding segmentation of PV parameters in the proposed method was used in the jetty scanning method. Zhanjiang, Fujian, and Berkeley data were used for the test. Because a connected water-land segmentation result is needed to perform jetty scanning, the water extraction result was first processed by small area removal. The detection results are shown in Figure 12. The water-land segmentation results of the proposed method are shown in Figure 12a1-c1. The detection results of the proposed method are shown in Figure 12a2-c2. The water-land segmentation results obtained by the process of small area removal are shown in Figure 12a3-c3. We can see that the processed water-land segmentation result is wrong in the Zhanjiang data because of the wide intertidal flat in Figure 12a3. There are some wrong segmentation pixels along the cross-sea bridge due to the scattering interference in Berkeley in Figure 12c3. The detection results of the comparison method are shown in Figure 12a4-c4. For the comparison method, there are many false alarms with the Zhanjiang data due to the wrong water-land segmentation result in Figure 12a4. There are many false alarms with the Fujian and Berkeley data due to the natural protruding terrain along the coast in Figure 12b4,c4. The number of false alarms and the IoU index of the comparison method and the proposed method are listed in Table 5. The table shows that the numbers of false alarms of the comparison methods are 72, 17, and 16, and the IoU values of the detected target port are 25.18%, 1.36%, and 17.4% for the three data, respectively. Compared with the proposed method, the number of false alarms of the comparison method is much larger, and the IoU value is much lower. We can conclude that the performance of the proposed method is much better since all ports are correctly detected and no false alarms are detected by the proposed method.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Data** & **Zhanjiang** & **Fujian** & **Berkeley** & **Tianjin** \\ \hline \(m_{PV}\) & 0.0132 & 0.0023 & 0.0016 & 0.0014 \\ \(th_{PV}\) & 0.0659 & 0.0114 & 0.0081 & 0.007 \\ \(m_{PRDV}\) & 1.0880 & 0.6898 & 0.8714 & 1.2946 \\ \(th_{PRDV}\) & 3.2430 & 1.5020 & 1.9500 & 2.8540 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Thresholds of the PV and PRDV in the Zhanjiang, Fujian, Berkeley, and Tianjin data, where \(m_{PV}\) denotes the average volume power of the sampling region, and \(m_{PRDV}\) denotes the average ratio parameter in the extracted water region.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Data**} & \multicolumn{2}{c}{**Jetty Scanning Method**} & \multicolumn{2}{c}{**The Proposed Method**} \\ \cline{2-5}  & **FA** & **IoU** & **FA** & **IoU** \\ \hline Zhanjiang & 72 & 25.18 & 0 & 75.38 \\ Fujian & 17 & 1.36 & 0 & 66.73 \\ Berkeley & 16 & 17.4 & 0 & 77.80 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Performance comparison of the proposed method with the jetty scanning method, where ’FA’ stands for the number of false alarms.