High-resolution near-shore geophysical survey using an Autonomous Underwater Vehicle (AUV) with integrated magnetometer and side-scan sonar

English Abstract:

Autonomous underwater vehicles (AUVs) give many advantages over traditional boat-towed survey methods, including the ability to operate under most sea states, and the ability to collect data at very high spatial resolution, which is a significant benefit for archaeological investigation. Integration of magnetometer sensors on AUVs has been problematic due to the magnetic interference produced by the AUV thrusters and electronics. In this study, we evaluated an AUV-deployed magnetic survey system consisting of an Overhauser magnetometer (Marine Magnetics Explorer) mated to a portable AUV (OceanServer Iver2). To eliminate magnetic interference from the AUV, the magnetometer was tethered to the AUV with a 5m tow cable, as determined by static and dynamic instrument testing, which indicated no detectable magnetic influence at this distance. The system was evaluated in a survey collected over a shallow water test area in Lake Ontario near Toronto, Canada and compared directly with the results of a conventional boat-towed magnetic survey. The AUV magnetic data have equivalent long-wavelength accuracy to the boat-towed data as determined by tie-line error analysis. The AUV data were shown to have less high frequency noise, and were able to identify a number of small ferromagnetic targets that were undetected in the boat-towed magnetic data.