A Measurement Quality Factor for Swath Bathymetry Sounders

The quality estimation associated with individual soundings measured and computed by swath bathymetry sonars is a paramount issue which is most often imperfectly addressed today by sonar manufacturers. In this paper, a unified definition is proposed for a quality factor usable for all swath bathymetry sonars; the depth-relative error is directly estimated from the signal characteristics used in the sounding computation. The basic algorithms are presented for both phase-difference (oblique incidence) and amplitude (normal incidence) detection, and can be readily implemented in any swath bathymetry system using these detection principles. This approach gives a direct access to the objective bathymetric performance of individual soundings, and hence avoids the explicit estimation of intermediate quantities such as the signal-to-noise ratio (SNR). It makes possible intercomparisons between different systems (multibeam sounders versus interferometric sonars) and processing principles (phase difference versus amplitude); it is expected to provide a useful input to bathymetry postprocessing software using quality estimation of individual soundings.