SeaWASP: A small waterplane area twin hull autonomous platform for shallow water mapping

Students with Santa Clara University (SCU) and the Monterey Bay Aquarium Research Institute (MBARI) are developing an innovative platform for shallow water bathymetry. Bathymetry data is used to analyze the geography, ecosystem, and health of marine habitats. However, current methods for shallow water measurements typically involve large, manned vessels. These vessels may pose a danger to themselves and the environment in shallow, semi-navigable waters. Small vessels, however, are prone to disturbance by the waves, tides, and currents of shallow water. The SCU / MBARI autonomous surface vessel (ASV) is designed to operate safely, stably in waters > 1 m and without significant manned support. Final deployment will be at NOAA's Kasitsna Bay Laboratory in Alaska. The ASV utilizes several key design components to provide stability, shallow draft, and long-duration unmanned operations. Bathymetry is measured with a multibeam sonar in concert with DVL and GPS sensors. Pitch, roll, and heave are minimized by a Small Waterplane Area Twin Hull (SWATH) design. The SWATH has a submerged hull, small water-plane area, and high mass to damping ratio, making it less prone to disturbance and ideal for accurate data collection. Precision sensing and actuation is controlled by onboard autonomous algorithms. Autonomous navigation increases the quality of the data collection and reduces the necessity for continuous manning. The vessel has been operated successfully in several open water test environments, including Elkhorn Slough, CA, Steven's Creek, CA, and Lake Tahoe, NV. It is currently is in the final stages of integration and test for its first major science mission at Orcas Island, San Juan Islands, WA, in August, 2008. The Orcas Island deployment will feature design upgrades implemented in Summer, 2008, including additional batteries for all-day power (minimum eight hours), active ballast, real-time data monitoring, updated autonomous control electronics and software, and data editing using in-house bathymetry mapping software, MB-System. This paper will present the results of the Orcas Island mission and evaluate possible design changes for Alaska. Also, we will include a discussion of our shallow water bathymetry design considerations and a technical overview of the subsystems and previous test results. The ASV has been developed in partnership with Santa Clara University, the Monterey Bay Aquarium Research Institute, the University of Alaska Fairbanks, and NOAA's West Coat and Polar Regions Undersea Research Center.