Seabed Transponder Localization Behavior from an Autonomous Surface Vehicle

Acoustic seabed transponders are widely used for autonomous underwater vehicle (AUV) navigation to mitigate the inherent drift of onboard inertial navigation systems. For these transponders to be effectively used by the AUV, their positions must be known prior to an AUV deployment. Transponder positions are commonly obtained via ship-based surveys, during which a vessel will drive a large circle around a transponder. This survey process is time-consuming, expensive, and an inefficient use of ship-time. By integrating sensors and software engineering, an Autonomous Surface Vehicle (ASV) is enabled to perform the transponder localization. Transponder data has been collected from local test events offshore La Jolla, California using a Wave Glider SV3-v300 (Boeing Liquid Robotics, Herndon VA). An at-sea survey was conducted with the ASV driving a clockwise circle around a stationary transponder. Concurrent GPS fixes and one-way acoustic travel times from the ASV sub component to the deployed seabed transponder were collected. Analysis of this data set indicates that to minimize Wave Glider survey time, only a 200-degree arc around the survey circle must be completed to optimize time spent on station with the survey's accuracy and precision in estimating the location of the transponder. This result matches with a theoretical analysis suggesting at least a 150-degree arc must be performed to achieve a reliable precision estimate of the transponder location.