Field Demonstrations of Precision Mapping and Control by the SUNFISH® AUV in Support of Marine Archaeology

Detailed underwater inspection or sampling tasks are often performed by human divers, often in difficult or dangerous conditions. Highly maneuverable, intelligent autonomous underwater vehicles have the potential to enhance or replace the most monotonous and difficult portions of this work to improve outcomes and reduce risks to divers. In this paper, we describe autonomous exploration, mapping, return-to-target, sediment sampling, and diver assistant capabilities developed for the small, hover-capable SUNFISH® AUV to enable marine archaeological investigation in unstructured, 3-D, overhead environments. SUNFISH is a compact, easily transportable vehicle, with full 6-DOF control. It is able to navigate in and build fully 3-D maps of complex underwater geometries such as cliffs, caves, and tunnels. The primary sensing is via a side-look multibeam sonar which can be used for survey and detailed 3-
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mapping. Additional sensors and actuators enable photogrammetry, precision inspection, and underwater intervention in these environments. SUNFISH employs a real-time sonar SLAM system and an exploration behavior to expand the mapped volume and safely find paths through 3-
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environments. Here we report on augmented vehicle capabilities enabling return to targets in the mapped volume, and intervention in the form of sediment sampling at a location specified in the 3-
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map. In May-June 2023, we demonstrated these capabilities in a field deployment as part of the Our Submerged Past project. This project aims to uncover evidence of prehistoric human habitation on the continental shelf west of Prince of Wales Island in Southeast Alaska by exploring, mapping, and sampling currently submerged caves and rock shelters that would have been exposed at times in the last 17,000 years. In this project, the SUNFISH AUV demonstrated the ability to autonomously survey an area, return to targets identified in its high-precision 3-D map, take sediment samples, and assist human divers in archaeological tasks. Lessons learned in applying a cutting-edge AUV to investigate and document archaeological sites in this project can serve to enable new types of investigations, and streamline and reduce costs of archaeological and other assessments in the future.