# LCAS-DetNet: A Ship Target Detection Network for Synthetic Aperture Radar Images
## 3 Materials and Experiments  
### Datasets  
We selected the HRSID [31] and SSDD [32] datasets for the training and validation of our proposed method. These datasets encompass a variety of scenes, such as islands, ports, and inland regions, offering a comprehensive range of environments for assessment. Further details are provided below.  
The HRSID [31] dataset stands as one of the most extensively utilized publicly accessible datasets in the field of SAR ship detection. It encompasses SAR imagery of ships featuring varied polarization modes, geographic regions, and resolutions, as shown in Figure 6. The HRSID dataset comprises 5604 high-resolution SAR images acquired by three high-resolution satellite sensors: TerraSAR-X, TandemiX, and Sentinel-1B. The images include three polarization modes, VV, HV, and HH, and the dataset contains a cumulative tally of 16,951 ship detection targets. The image resolutions in the HRSID dataset range from 0.5 m to 3 m per pixel. It encompasses diverse scenes including docks, nearshore areas, and ports, featuring 321 large, 7388 medium, and 9242 small ships. This distribution translates to proportions of 2% for large ships, 43.5% for medium ships, and 54.5% for small ships.  
The SSDD [32] dataset, also frequently employed in SAR ship detection research, contains raw SAR image data captured by three satellite sensors. The dataset encompasses four polarization modes, VV, VH, HH, and HV, with a count of 1160 images and 2456 annotated ship detection targets. The image resolution of the SSDD dataset ranges from 1 m to 15 m per pixel, covering various ship scenarios in open seas and coastal areas, as shown in Figure 7. The dataset includes a distribution of large, medium, and small ships, with quantities of 76, 935, and 1529, constituting proportions of 3%, 36.8%, and 60.2%.  
We provide significant details for the HRSID and SSDD datasets in Table 1. Moreover, we performed a statistical assessment regarding the distribution of large, medium, and small ships across both HRSID and SSDD datasets, presenting the findings through bar charts for visual clarity. The corresponding statistical data for the HRSID and SSDD datasets are depicted in Figure 8a,b. The analysis of the figures clearly reveals that small-sized ships predominate in both datasets, posing significant challenges for our ship detection endeavors.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Datasets** & **HRSID** & **SSDD** \\ \hline Image number & 5604 & 1160 \\ Ship number & 16,951 & 2551 \\ Polarization modes & VV, HV, HH & VV, VH, HH, HV \\ Image size (pixel) & 800 \(\times\) 800 & 500 \(\times\) 500, etc. \\ Resolution (m) & 0.5, 1, 3 & 1–15 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The significant information table for the HRSID and SSDD datasets.  
Figure 6: Image samples from the HRSID dataset exhibiting ships of diverse sizes amidst intricate scenes, including coastal regions, ports, and docks. The HRSID dataset includes vessels of large, medium, and small scales captured in diverse scenarios.  
Figure 7: Image samples from the SSDD dataset, annotated in PASCAL VOC format, showcasing ships of various sizes, including large, medium, and small vessels.