# Enhancement of Sentinel-2A Images for Ship Detection via Real-ESRGAN Model
## 3 Results and Discussion
### Training Object Detection Model  
In this phase, model training was conducted separately utilizing two distinct datasets: the Sentinel-2A satellite images and a dataset comprising Sentinel-2A satellite images \begin{table}
\begin{tabular}{l l} \hline \hline scale & 4 \\ gt\_size & 400 \\ queue\_size & 60 \\ network\_g & RRDBNet \\ network\_d & UNetDiscriminatorSN \\ optimizer & Adam \\ total\_iter & 200,000 \\ lr & 0.0001 \\ num\_worker\_per\_gpu & 5 \\ batch\_size\_per\_gpu & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Hyperparameters of Real-ESRGAN model. Figure 3: Comparison of the Sentinel 2A image (**left**) and the enhanced Sentinel 2A image (**right**): (**a**) Port of Piraeus; (**b**) Port of Amsterdam; (**c**) Port of Hong Kong; (**d**) Port of Nantong. enhanced using the Real-ESRGAN model, which had been developed in the preceding phase. The YOLOv10-m model of the YOLOv10 architecture was employed for the ship detection task. This training was conducted in a Kaggle environment, utilizing an NVIDIA Tesla GPU with 16 GB of memory. Early stopping with a specified patience parameter was implemented to mitigate the risk of overfitting during the training process. The performance evaluations derived from the model training are presented in Table 5. The Precision-Recall curve of the ship detection is illustrated in Figure 4. The experiments confirm that there has been a 2.9%, 1.3%, 2.6%, and 2.6% increase in the Precision, Recall, mAP50, and mAP50-95 metric values, respectively. These results indicate that enhanced images significantly contribute to improving ship detection capabilities. A thorough visual examination of the results revealed significant improvements in ship detection within the enhanced images. Figure 5 compares detected ships in the Sentinel-2A images (left) with those in the enhanced Sentinel-2A images (right) for the Port of Zeebrugge and Port of Ningbo-Zhoushan. In Figure 5a, a moving ship and a ship close to the shore are identifiable. In Figure 5b, neither ship is detected in the original images; however, both become visible after enhancement. Figure 5c shows that the ship near the shore can be detected in both images, while the moving ship is only identifiable in the enhanced image. Figure 5d illustrates that ships are detectable in both images, but in the Sentinel-2A image, the wave created by the ship is mistakenly recognized as a ship itself; this error is corrected in the enhanced Sentinel-2A image. The results indicate that the enhancements significantly improve ship detection. Furthermore, the textures recovered using Real-ESRGAN display a realistic and smooth quality. The enhancements applied to the Sentinel-2A images resulted in improved clarity and reduced blurriness. The enhanced Sentinel-2A images are not only visually striking, featuring sharper edges of the ships, but they also preserve a realistic appearance despite the increased sharpness. Figure 4: The Precision–Recall curve of the ship detection for (**a**) the Sentinel-2A images and (**b**) the enhanced Sentinel-2A images. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Data** & **Precision (\%)** & **Recall (\%)** & **mAP50 (\%)** & **mAP50-95 (\%)** \\ \hline Sentinel-2A & 77.8 & 79.5 & 84.9 & 65.9 \\ images & & & & \\ Enhanced & & & & \\ Sentinel-2A & 80.7 & 80.8 & 87.5 & 68.5 \\ images & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Performance evaluation of the ship detection via YOLOv10 model. Another comparison detected ships using Sentinel-2A images (left) with enhanced Sentinel-2A images (right) in Figure 6, which focuses on the Port of Amsterdam and the Port of Zeebrugge. Figure 6a shows that no ships are detected in the Sentinel-2A image on the left; however, after enhancement, two ships are identified. Visually assessing the results indicates that while ships can be detected, some remain undetected. Furthermore, in Figure 6b, a ship is identified in the Sentinel-2A image, but after enhancement, the waves along the shore are also misidentified as ships.