Acoustic correlation sonar for vertical profiling of ocean currents to a range of 1 km

Ocean current profilers, based on spatial or temporal correlation analysis of sound backscattered from passive targets drifting with the current, have several potential advantages over the more common Doppler profilers. Correlation profilers can operate over a longer range with smaller, lighter and cheaper transducers. However, the signal processing is more complex and computationally intensive, increasing transmission intervals and leading to difficulties understanding when and why the performance is poor. Using data gathered from RRS Discovery in early 1995 the authors describe the performance of a 22 kHz acoustic correlation current profiler and compare its results with a lowered acoustic Doppler profiler. At low ship speeds, the signal to noise ratio was sufficient to allow profiling to 1 km depth, with the achievable range reducing as speed increased. Bias and decorrelation occurred in the upper 160 m owing to unknown causes and greatly reduced data quality