## 4 Results
### Results with Dual-Polarimetric Data
#### 4.2.3 Enhancement Performance with L-Band Dual-Pol Data  
The last set of results follows the same process applied to the Radarsat-2 image in Section 4.2.2, but using the L-band image acquired by ALOS-1 over Tokyo Bay. As in the previous example, we manually select the same sea pixel as a reference for the three dual-pol optimizations. This reference pixel is also the same one used for the quad-pol optimization of this image, detailed in Section 2.1. Additionally, the same vessel is used to plot transects and calculate signal-to-noise ratios, ensuring a fair comparison of the optimization across different polarization inputs.  
Figure 10: Optimization results of dual-polarimetric [HH_HV] image acquired by Radarsat-2 over the city of Barcelona (Spain). Figures (**a–c**) represent the image intensity in logarithmic scale ranging from \(-35\) to \(0\) dB.  
The results for the three dual-pol combinations--HH, VV, HH, HV, and VV, VH--are presented in Figures 13, 14, and 15, respectively. As evident from these figures, the optimized images consistently exhibit the highest contrast. Furthermore, the transects in Figures 14d and 15d consistently show a greater difference between the peak and the sea signal in the optimized channels (red plots) compared to the original channels (blue and green plots). This difference is particularly pronounced when optimization is applied using the [HH, VV] combination, as shown in Figure 13d. In this case, sea clutter is reduced to below \(-35\) dB (compared to \(-10\) dB in the original channels), while ship  
Figure 11: Optimization results of dual-polarimetric [VV,VH] image acquired by Radarsat-2 over the city of Barcelona (Spain). Figures (**a**–**c**) represent the image intensity in logarithmic scale ranging from \(-35\) to \(0\) dB.  
intensity increases slightly to approximately 10 dB (compared to around 8 dB in the HH and VV polarizations).  
Figure 12: Optimization results of dual-polarimetric [VV,VH] image acquired by Sentinel-1 over the Strait of Gibraltar. Figures (**a**–**c**) represent the image intensity in logarithmic scale ranging from \(-35\) to \(0\,\mathrm{dB}\).  
Additionally, as illustrated in Figures 14d and 15d, ship intensity in the optimized channels is very similar to that of the cross-polar channels (HV and VH) (around 0 dB). However, the sea intensity level is significantly reduced, further demonstrating that the optimized channels provide the best contrast for ship detection.  
Lastly, an estimation of the signal-to-clutter ratio for the three optimization cases is summarized in Table 7. As can be seen, the optimum channel always exhibits the highest values, thus proving again the benefits for ship detection.  
Figure 13: Optimization results of dual-polarimetric HH,VV image acquired by ALOS-1 over Bay of Tokyo (Japan). Figures (**a–c**) represent image intensity in logarithmic scale ranging from \(-35\) to 0 dB.  
Figure 14: Optimization results of dual-polarimetric [HH,HV] image acquired by ALOS-1 over Bay of Tokyo (Japan). Figures (**a**–**c**) represent image intensity in logarithmic scale ranging from \(-35\) to \(0\) dB.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Processed Polarimetric** & \multicolumn{3}{c}{**{[HH,VV]**}} & \multicolumn{3}{c}{**{[HH, HV]**}} & \multicolumn{3}{c}{**{[VV,VH]**}} \\
**Channels** & & & & & & & & & \\ \hline Signal-to-Clutter & HH & VV & OPT & HH & HV & OPT & VV & VH & OPT \\ Ratio [dB] & 15.26 & 13.81 & 43.17 & 15.26 & 21.37 & 29.73 & 13.81 & 21.37 & 29.85 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Signal-to-clutter ratio between a ship and its surrounding sea area after applying the contrast enhancement method with different dual-pol combinations of channels using L-band ALOS-1 data.