SAR Ship Detection Based on Explainable Evidence Learning Under Intraclass Imbalance

Synthetic aperture radar (SAR) ship detection is an important technology supporting water traffic monitoring and marine safety maintenance. In recent years, many methods based on deep neural networks (DNNs) have been used to improve the performance of SAR ship detection. These methods mainly focus on two issues: one is the false alarm of ship detection in complex inshore environments, and the other is the effective extraction and utilization of SAR ship features. The topic discussed in this article is one of the culprits that has caused the aforementioned two problems but has long been overlooked. Specifically, it pertains to the issue of intraclass imbalance in SAR ship detection. There are imbalances in the size distribution, azimuth distribution, and background distribution under the real data collection environment. However, since SAR ship detection is a single-class detection task, the aforementioned imbalances lack reliable descriptors during training. This article proposes using evidence learning to obtain the epistemic uncertainty as a descriptor of biased learning on samples. Contrastive learning is used to further utilize the uncertainty label of samples to correct biased learning under intraclass imbalance. The proposed method is proven to be effective on multiple network models. AP50 reaches 94.8% on the HRSID dataset, 98.4% on the SSDD dataset, and 80.9% on the LS-SSDD dataset, both achieving SOTA performance.