Reconstruction of 3D shape from sidescan sonar images using shape from shading technique

Side scan sonar (SSS) is one of the most widely used imaging systems in the underwater environment. It is relatively cheap and easy to deploy in comparison with more powerful sensors like multibeam echosounder or synthetic aperture sonar. Although, the SSS does not provide directly the seafloor bathymetry measurements. Its outputs are usually in a form of grey level acoustic images of seafloor. However, the analysis of such images performed by human eye allows creating semi-spatial impressions on seafloor relief and morphology. The 3D shape reconstruction from 2D images using SFS approach is one of classical problems in computer vision. In the paper, the method based on Shape From Shading (SFS) technique for SSS images processing is presented. The 3D seafloor relief is reconstructed using the information from both the currently processed and previous ping. The seafloor backscattering coefficient dependence on an incident angle, which is needed in the applied SFS algorithm scheme, is being estimated in the experimental way, i.e. by analysis of SSS image contents for the flat seabed region.