Theory and Signal Processing of Acoustic Correlation Techniques for Velocity Measurement of Vessel

The theoretical model and signal processing of correlation techniques to estimate the velocity of a vessel relative to the bottom are discussed. When the random component of velocity is considered, the sonar space-time correlation function of bottom reverberations within Fraunhofer zone is derived. The function, which is composed of zero order, first order and second order Bessel function, is the theoretical model of acoustical correlation techniques. By the model, “wave invariance” can be well described. Localized least mean squares (LLMS) criterion is put forward for velocity measurement. Sequential quadratic programming (SQP) method is adopted as the optimization method. A prototype correlation velocity log (CVL) underwent several deep sea trials, the results show that theoretical model approximately coincides with experimental data. Square loop tracklines of the ship in 3560 m deep area were adopted to examine the performance of CVL. Varying velocity cruise test and drifting test were also carried out. The CVL performed well in these tests. A least squares linear regression shows a significant correlation between the speeds of CVL and those of GPS. The rms error of CVL is less than (1.4%v+3) cm/s, where v is the velocity of vessel.