A novel sonar target detection and classification algorithm

Underwater target detection and classification based on sonar images is a challenging task because of the complex underwater environment. In recent years, deep learning technology has effectively improved the detection accuracy of underwater targets compared to traditional sonar image target detection methods, which have a low accuracy and poor robustness. However, deep learning algorithms for sonar image target detection have fewer training samples and a low detection speed. To solve these problems, an improved YOLOv4 based sonar target detection and classification algorithm is proposed in this paper. First, the feature extraction network CSPDarknet-53 in YOLOv4 is improved to reduce both the model parameters and the network depth. Second, the PANet feature enhancement module in the YOLOv4 model is replaced by the adaptive spatial feature fusion module (ASFF) to obtain a better feature fusion effect. In addition, the number of fusion feature layers is increased to improve the receptive field and detection accuracy. Furthermore, this paper uses the k-means++ algorithm to cluster the sonar image dataset to obtain the appropriate size and number of anchor boxes for model training. The experimental results show that the proposed method has better performance in detection accuracy and detection speed compared to YOLOv4 and YOLOv4-tiny.