Underwater navigation and mapping in complex underwater overhead environments—whether natural (underwater caves, under-ice environments) or man-made (pipes, aquaducts, flooded mines)—presents significant challenges. Such environments are often remote, unstructured, and lack infrastructure for precise external positioning systems; navigation aids which require some kind of access to the surface—such as GPS or USBL—are unavailable; and recovery often requires precisely navigating back to the deployment location. Navigation is thus heavily reliant on dead reckoning, which is prone to cumulative errors and positional drift over time.
In order to operate in these types of environments, we developed the SUNFISH® AUV, a person-portable system designed for agile maneuvering in 3D spaces. It utilizes acoustic Simultaneous Localization and Mapping (SLAM) augmented with georeferenced initialization and updates to achieve precision 3D underwater survey and mapping. The AUV’s multibeam sonar captures data for high-resolution 3D mapping. To counteract drift and ensure georeferencing, the system incorporates control points such as surface RTK GNSS fixes or sub-surface radiolocation beacon fixes.
We have demonstrated the effectiveness of this approach in several field projects, including natural springs, sea caves, and blue holes. Our vehicle and data processing system are able to produce high-resolution models of complex 3D environments with varying scales and ambient conditions. These applications highlight the SUNFISH AUV’s capability for georeferenced 3D survey, inspection, and mapping in challenging underwater overhead environments.
