A method to enhance the noise robustness of correlation velocity measurement using discrete wavelet transform

Navigation at sea requires accurate velocity measurement of a vehicle relative to the seabed. Correlation velocity measurement techniques are efficiently used to measure the velocity of underwater vehicles because they are not affected by sound speed compared to Doppler techniques, have several advantages such as small size and power consumption and tracking deep seabed. We consider the relationship of maximum correlation coefficient and signal-to-noise ratio (SNR), which are important parameters in correlation velocity measurement and present the maximum correlation coefficient equation according to SNR. Next, we propose a method of the noise robustness enhancement using discrete wavelet transform (DWT) in correlation velocity measurement. In addition, we evaluate the noise robustness of the proposed method and various methods of correlation velocity measurement through simulation, and present the maximum correlation coefficient equation according to SNR of our method. Simulation results show that new method of correlation velocity measurement using wavelet thresholding proposed in this paper improves the noise robustness of correlation velocity measurement more than various methods. In addition, in correlation velocity log (CVL) operating under low SNR below 6 dB, the maximum correlation coefficient of new method increases more than 0.1 than the classical method. Simulation results show that the new method of correlation velocity measurement considerably improved the noise robustness of spatial CVL than classical method, and the noise robustness of new method is highest among various methods of correlation velocity measurement.