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www.sea-technology.com October 2015 / st 45 M icrorelief, deposition processes and water dynamics in shallow water at an offshore estuary or continen- tal shelf are affected by natural geographical factors or hu- man economic activities. Some of these rapid changes can lead to submarine disasters and other fatal consequences, and can infuence the development of the ocean economy, channel safety, marine engineering safety and coastal se- curity. How to supervise, study, prevent, manage and even utilize these local relief changes has become a hot topic in coastal oceanography and deposition kinetics. Usually, single-beam echosounders, multibeam bathym- etry, side scan sonar, underwater cameras and portable land- form scanners are used for the detection of relief changes in shallow water. But they all have weaknesses. Single-beam, multibeam bathymetry and side scan sonar are designed for moving surveys, rather than in-situ observation. They are also costly. Traditional landform scanners don't adapt to complicated terrain changes and mechanism studies that are the focus of deposition kinetics. Underwater cameras are nonprofessional equipment that require more precision and safety. To address these gaps, a 3D remote profling sonar has been designed by Marine Electronics Ltd. for in-situ obser- vation of microrelief in shallow water. It can acquire local relief data repeatedly and periodically for half a month or more, according to the parameters set. Three-dimensional terrain models can be constructed within each recording cycle, and high-resolution changes of the local relief can be seen. This tool has applications for marine geology, ocean charting, physical oceanography and sediment dynamics. The 3D remote profling sonar comprises relatively in- dependent units: a scanning sonar system (including trans- mitting, receiving and processing unit), programming lead (used in debugging or parameter setting), PC interface unit, battery bin (used only in offine mode), detachable storage unit, and corresponding lines and adapters. There are two modes: online and offine. In online mode, a 30-m-long cable is utilized to link the scanning sonar (un- derwater unit) to a PC terminal on board a ship. With the USB cable plugged in, the sonar can be controlled directly by the 3D profling software on the PC. In offine mode, the sonar is programmed prior to deployment by connecting a USB cable to the Windows-compatible PC under the con- trol of the 3DProgrammer software package. Online Mode Before the formal start of an investigation, a stability test and parameter setting should be done. The programming lead and an RS485-to-USB converter are needed to connect the sonar with the PC terminal. The driver of the USB adapt- er should be installed and the virtual RS232 port should be set frst. Supplied with the system is a Windows program Tool for In-situ Observation Of Microrelief in Shallow Water 3D Remote-Profling Sonar in Lingdingyang Estuary By Dr. Jihong Shang (Top) Displays from the observation system. (Bottom) System connection diagram of the 3D remote profling sonar.