Reducing elevation angle errors of long-range deep-sea acoustic localization by ray tracing and depth measurements

Abstract

For deep-sea (robotic) applications, accurate acoustic localization is required, e.g. using USBL devices. Internal calculations for these devices usually assume a constant sound velocity within the deployment area ignoring refraction effects due to a depth-dependent sound velocity profile. This work presents the results of long-range deep-sea (5000m) USBL localization tests to estimate absolute positioning accuracy. The experiments lead to a correction approach by incorporating both the depth of acoustic participants as well as the full sound velocity profile. For bigger horizontal distances (> 800m), this approach can largely reduce the resulting (systematic) elevation angle error.