3D Bathymetry via USV USV with Multibeam Echosounder for Shanghai Bridge Survey By Taxiya Wang he Donghai Bridge, located in Shanghai, China, is a key component of the Shanghai International Shipping Center's deepwater port infrastructure. Conducting underwater surveys of the bridge piers” conditions for maintenance purposes is an operational challenge. The bottom of the bridge piers is immersed in water and can be eroded by the action of sand and gravel. Hydrodynamic scour caused by rapid water Donghai Bridge, Shanghai. (Inset) The CHCNAV APA Donghai Bridge piers. - flow can create scour holes...

solution selected for the Donghai Bridge project comprises an unmanned survey vesAPACHEG6 of CHCNAY, carrying a NORBIT STX multibeam echosounder. Flexible Deployment When conducting multibeam bathymetric surveys with an unmanned surface vessel, marine survey professionals highlight three major points of concern: secure is their investment given the cost of multibeam echosounders? Does the USV offer sufficient flexibility to handle a variety of bathymetric survey scenarios? What about the final accuracy of the high-resolution 3D bathymetric survey? Maneuverability and ease of use in fast current...

(Top) Typical linear navigation course for multibeam echosounding. (Bottom) The APACHE6 USV approaching a bridge pier. During a turn, the hull automatically decelerates so that the unmanned vessel's sounding line is at the same height as the intended line to ensure underwater data integrity throughout an operation. Multibeam Coverage Marine drones have to incorporate efficient automatic navigation control technology to follow the planned route in a complex working environment, with different speeds and changes in flow direction. The objective is to have a trajectory deviation of less than 20...

surface sound velocity and other data can be transmitted with a single interface cable for easy installation and use and to minimize the risk of damage. When the USV is stationary, the STX multibeam echosounder, in addition to its 210° horizontal scan cover- age, also has 20° longitudinal scan coverage, so that the real-time dynamic 3D scanning effect can be achieved. During multibeam sounding, the USV moves along the sounding line at a controlled constant speed of 4 to 6 kt. The display, control and data acquisition software that supports multibeam sounding runs on the data acquisition computer...

(Top) Bridge section piling and water bottom scouring rendering. (Bottom) view underwater scour details. tained throughout this survey with the original bridge construction design to determine if additional riprap was required. After data post-processing and analysis, a total of 18 piles were identified for further investigation for routine maintenance. difficult to achieve this with traditional crewed hydrographers now have the option of deploying USVs. USVs reduce survey time, improve work efficiency and produce high-resolution 3D data to meet the requirements of the most demanding marine infrastructure...