Automatic Overlapping Area Determination and Segmentation for Multiple Side Scan Sonar Images Mosaic

Seafloor image is important for marine scientific research and ocean engineering. With the wide use of side scan sonar (SSS), multiple measured SSS images need to be mosaicked to form a large-scale and high-resolution seafloor image. This article proposes an automatic mosaic method. First, the overlapping areas between adjacent strips are determined automatically by the track lines and swath width. In the overlapping areas, the image matching is conducted using the speeded-up robust features algorithm with the constraint of geographic coordinates of detected feature points. Then, the overlapping area is segmented using the k-means cluster method. Within each segmented region, the coordinate transformation model is established to make the positions of common features in the overlapping areas unique. With regards to multiple SSS images mosaic, the method to mosaic in sequence is also proposed according to the permutation parameter of each strip. Finally, the SSS images in the overlapping areas are fused and a large-scale seafloor image is formed. This proposed method was applied in one water area of Shenzhen, demonstrating good performance in terms of coordinate consistency of the same features in the mosaicked image. The mean coordinate deviations of the same feature points in overlapping areas were nearly zero and the standard deviation of them also decreased. This proposed method is easily transferable to other study areas and provides an objective, repeatable means for multiple SSS images mosaic.