Theory and signal processing of acoustic correlation techniques for current velocity measurement

A theoretical model and signal processing of acoustic correlation measurements to estimate current velocity are discussed.The sonar space-time correlation function of vol- ume reverberations within Fraunhofer zone is derived.The function,which is in exponential forms,is the theoretical model of acoustic correlation measurements.The characteristics of the correlation values around the maximum of the amplitude of the correlation function,where most information about current velocity is contained,are primarily analyzed.Localized Least Mean Squares (LLMS) criterion is put forward for velocity estimation.Sequential Quadratic Programming (SQP) method is adopted as the optimization method.So the systematic sig- nal processing method of acoustic correlation techniques for current velocity measurement is established.A prototype acoustic correlation current profiler (ACCP) underwent several sea trials,the results show that theoretical model approximately coincides with experimental re- sults.Current profiles including the speed and direction from ACCP are compared with those from acoustic Doppler current profiler (ADCP).The current profiles by both instruments agree reasonably well.Also,the standard deviation of velocity measurement by ACCP is statistically calculated and it is a little larger than predicted value.