Seafloor obstacle detection by sidescan sonar scanlines for submarine cable construction

摘要

This study proposes an online seafloor obstacle detection method using sonar scanlines for submarine cable construction application. It is necessary to find out the obstacles, such as natural or linear artificial reefs and out of service cables or pipelines on the seabed along the proposed corridors of cable route for future route design jobs. And sonar system is almost the popular tool for this kind of survey. The sidescan sonar (SSS) produces an image representation by the backscattering and reflection of signals to show the seabed morphology and features. A seafloor feature searching and detecting method in the article using sonar scanlines instead of sonar images is developed to reduce the computation and speed up the processing. There are three steps of the procedure. Firstly, a pre-processing step is applied to filter the data and to reduce computation time. Then, a detector is designed to detect the obstacle by a scanline and represent obstacles with different classification. Finally, every individual scanlines are located and corrected on an obstacle map for further application. An experimental result conducted on a combined seafloor with muddy, sandy and rocky seabed was demonstrated to show every individual obstacle locations and its track on the chart automatically. The proposed detecting method implement online because of it provide efficient than traditional image processing method. The map of obstacles on the proposed corridors is useful for future route design, clearance and pre-lay grapnel run jobs. The online detection not only evaluates the efficient of route survey but also saving the funding of submarine construction.