Automated Optimal Processing of Phase Differencing Side-scan Sonar Data using the Most Probable Angle Algorithm
Phase-differencing side-scan sonar systems produce co-located bathymetry in addition to each side-scan amplitude measurement. Bathymetric soundings are calculated from the range to each measurement (derived from the two-way travel time) and the receive angle of the incoming signal. Because phasedifferencing systems produce a seafloor sounding with each individual measurement, they are often characterized as noisy when compared to multi-beam sonar systems, whose seafloor estimates, whether by amplitude-weighted mean or sub-aperture phase difference detection, are the product of averaging several measurements. In addition, every effort is made to increase the resolution of side-scan data by increasing the bandwidth and sampling rate of the transmitted signal, often producing more than 10,000 data points per ping. This volume of outlier-prone, relatively noisy data is difficult for operators to interpret and software to process. A series of methods has been developed for the automated processing of phase-differencing side-scan sonar data producing seafloor estimates and related uncertainties optimized for the survey application. The “Most-Probable Angle Algorithm” (MPAA) has been developed for the filtering of outliers in range-angle measurements. With outliers removed, the uncertainty of the filtered measurements are estimated. Angle estimates are then calculated as an uncertainty-weighted mean where the number of measurements contributing to each estimate is determined from that required to achieve a desired depth uncertainty. The resulting swath of depth measurements contains irregularly spaced soundings, typically obtaining full spatial resolution of the side-scan data from 20-50 degrees from nadir, and combining several measurements to reduce the uncertainty elsewhere. In this way, given a survey requirement, an optimal amount of information can be extracted from the sonar data in varying conditions.
Center for Coastal and Ocean Mapping
Journal or Conference Title
Digital Object Identifier (DOI)
V. E. Schmidt, T. C. Weber, and A. C. Trembanis, "Automated optimal processing of phase differencing side-scan sonar data using the most-probable angle algorithm," in 2012 Oceans, Institute of Electrical & Electronics Engineers (IEEE), 2012.