Integrated autonomous underwater vehicle (AUV) and marine Overhauser magnetometer for high-resolution marine archaeological survey.

Autonomous underwater vehicles (AUVs) are ideal platforms for geophysical survey of underwater archaeological sites, as they are capable of high-resolution navigation and can be deployed under any sea state. Magnetometers have been difficult to integrate with AUVs because of the strong magnetic fields produced by AUV motors and ferro-metallic components. In this study, an Explorer Overhauser total-field magnetometer was mated to an Iver2 AUV, creating the first practical and commercially available AUV-deployed magnetic survey system. To eliminate interference from the AUV, the magnetometer was towed behind the AUV at a distance of 5m, as determined by static and dynamic testing. The results of the magnetic tests are presented, along with field data from a test area in Lake Ontario near Toronto, Canada. AUV-acquired data were compared directly with a conventional boat-towed magnetic survey of the same area. The AUV magnetic data were of superior quality despite being collected in rough weather conditions that would have made conventional survey impossible. The resulting magnetic maps clearly identify several buried and surface targets that were verified with side scan sonar imaging.