Empirical uncertainty in angle of arrival estimation for bathymetric sidescan sonars

In most bathymetric sidescan sonars, phase differences measured across one or more pairs of transducer staves are used to estimate the angle of arrival of bottom echoes. In this work, uncertainties in these estimates are empirically determined from data obtained in 10-25 m of water depth with an L-3 Klein Associates 5000 V2 sidescan sonar operating at 455 kHz. Empirical angular uncertainties remained below 0.2° at the 95% confidence level out to horizontal ranges of 5.5 times the altitude of the sonar above the bottom. In addition, at the output of each phasor used to estimate angles of arrival, the signal-to-noise ratio is shown to provide a threshold below which angle of arrival estimates should be rejected because of acoustic shadows or multipath interferences.