A False Alarm Suppression Method Via Selective Anchor Generator for Ship Detection in Sar Images

Mainstream CNN-based SAR ship detectors are prone to produce false targets in the land area, which has a great relationship with the anchor generation mechanism in the network structure. The anchor generator will indiscriminately generate a set of anchors for each point on the predicted feature map and map it back to the original image. These anchors will become the initial candidate boxes after screening. Considering that ship targets in SAR images are usually small and sparsely distributed, this dense anchor generation method can easily generate candidate boxes in land areas. To solve this problem, this paper proposes a method to guide the generation of anchors through image area information, called selective anchor generator (SAG). Unlike previous anchor generator, SAG will do sea-land segmentation for image first and then establish a mapping relationship with the feature map. Points on the feature map that only contain land feature information are marked as negative points with no anchors being generated. In this way, the number of candidate prediction boxes in the land area is greatly reduced, thereby achieving the effect of false alarm suppression. Experiments on test data show that this method can effectively reduce the number of false targets generated in land areas.