Differential Phase Estimation with the SeaMARC II Bathymetric Sidescan SonarSystem

摘要

A maximum likelihood estimator is used to extract differential phase measurementsfrom noisy seafloor echoes received at pairs of transducers mounted on either side of the SeaMARC II bathymetric sidescan sonar system. Carrier frequencies for each side are about 1 kHz apart, and echoes from a transmitted pulse, 2 ms, long, are analyzed. For each side, phase difference sequences are derived from the full complex data consisting of base-banded and digitized quadrature components of the received echoes. With less bias and a lower variance, this method is shown to be more efficient than a uniform mean estimator. It also does not exhibit the angular or time ambiguities commonly found in the histogram method currently used in the SeaMARC II system. A figure for the estimation uncertainty of the phase difference is presented and results are obtained for both real and simulated data. Based on this error estimate and an empirical verification derived through coherent ping stacking, a single filter length of 100 ms is chosen for data processing applications.... Seafloor mapping system, Differential phase estimation, Swath bathymetry sidescan sonar.