An Ocean Current Profiler Using Doppler Sonar

An instrument for remote measurement of horizontal current distributions versus depth in the upper ocean has been developed. The system is based upon a standard Doppler navigation sonar which has been modified to optimize its performance as a current profiler. Reliable measurements of currents to depths in excess of 100 meters have been demonstrated with depth resolution of 3 meters. The current profiling system can be used on a moving ship or a stationary platform. The system is a pulsed 300 kHz sonar employing a four-beam "Janus configuration" transducer array. Time gated measurements of the Doppler frequency shift are made from the water mass scattered signals. These measurements are converted to depth segmented current velocity components in the ship's horizontally-referenced coordinate frame. Velocity measurements are coupled via an IEEE-488-(1975) standard general purpose interface bus (GPIB) to a CRT terminal. The terminal provides a real time CRT display and cassette tape recording of the smoothed two-axis currents versus depth.