LMO-YOLO: A Ship Detection Model for Low-Resolution Optical Satellite Imagery

It has been observed that the existing convolutional neural network (CNN)-based ship detection models often result in high false detection rate in low-resolution optical satellite images. This problem arises from the following factors: 1) the current 8-b rescaling schemes make the images lose some important information about ships in low-resolution imagery; 2) the effective features of ships at low resolution are far fewer than those of ships at high resolution; and 3) the detection of low-resolution ships is more sensitive to object-background contrast variation. To solve these problems, a low-resolution marine object (LMO) detection YOLO model, called LMO-YOLO, is proposed in this article. First, a multiple linear rescaling scheme is developed to quantize the original satellite images into 8-b images; second, dilated convolutions are included in a YOLO network to extract object features and object-background features; finally, an adaptive weighting scheme is designed to balance the loss between easy-to-detect ships and hard-to-detect ships. The proposed method was validated by level 1 product images captured by the wide-field-of-view sensor on the GaoFen-1 satellite. The experimental results demonstrated that our method accurately detected ships from low-resolution images and outperformed state-of-the-art methods.