Real-time monitoring method of water depth using oblique incidence sonar in harbour channel

A novel real-time monitoring method using the oblique incidence sonar is proposed to realize the in situ measurement of water depth in harbour channel. Making use of the multipath propagation structure of underwater acoustic channel, the method obtains the depth values by calculating the relative time delay of acoustic signals between the direct and the shortest bottom reflected paths. Bistatic transducer pairs are employed to transmit and receive the acoustic signals, and the GPS time synchronization technology is introduced to synchronize the transmitter and receiver. A hybrid algorithm combining the MODEX algorithm and nonlinear least-squares algorithm is used to obtain the super resolution estimation of multipath time delay. A practical system was developed, and two different types of experiments were conducted in shallow sea. Experimental results demonstrate that the method is feasible and the system is stable, efficient and with a good real-time performance.