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1 2008

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Ocean average current measurement using acoustic phase monitoring

Zieliński A., Zhou L., Butowski M.

Hydroacoustics

2008

Vol. 11

459-467

Knowledge of water currents is important in several ocean-related activities. Typically, current speed and direction are measured at a certain fixed location and depth (or depth profile) by a suitable current meter. In this paper, we propose a novel method for average current speed measurement along a path, based on acoustic phase monitoring. In this method, a transmitter and a receiver are installed at the ends of a designated path. A transmitted sinusoidal signal propagates along the path to the receiver. Intervening currents will introduce Doppler frequency shifts that can be measured as a rate of phase change in the received signal. The phase is recovered by means of a phase detector and unwrapping techniques. The desirable feature of the proposed method is that average current speed is monitored along the entire path. Moreover, the estimated frequency shift via the phase measurement achieves a higher accuracy in current measurement than does a measure of frequency directly by an FM demodulator.