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Feature Article

Manned Submersible Captures 3D Sonar Scans of Shipwrecks

By Stockton Rush
Co-Founder and CEO
Guillermo Söhnlein
Co-Founder and Chief Operating Officer
OceanGate Inc.
Miami, Florida

A full BV5000 3D sonar map of the AJ Goddard shipwreck.
Nautical archaeologists have long relied on scuba divers, underwater renderings, and photo and video imagery to catalog and describe shipwrecks. Yet despite recent technological advances, including side scan sonar, ROVs and AUVs, there are still few mechanisms in regular use for creating accurate and precise 3D maps of shipwrecks in low-visibility and deep-ocean conditions. This is due largely to a lack of funding as well as a dearth of submersible equipment companies willing to incur the upfront costs to develop the specialized skills necessary to tackle nautical archaeology projects.

OceanGate Inc. (Miami, Florida) has addressed this problem by integrating BlueView Technologies' (Seattle, Washington) 3D microbathymetry sonar system, the BV5000, on the manned, five-person submersible Antipodes, which is certified by the American Bureau of Shipping (ABS) and capable of reaching depths of 285 meters.

The BV5000 provides as much as a threefold increase in linear dynamic range and a fivefold increase in acoustic frequency in comparison to traditional sonar systems. The BV5000 combines high-resolution 3D profiling sonar, a mechanical pan-and-tilt device, and control and display software to generate both sector and 360-degree spherical scan data to create a 3D point cloud of an underwater structure, object or sce The BV5000's resulting data are analogous to laser scanner data, making it easy for ocean researchers to combine detailed underwater 3D acoustic mosaics with 3D laser scan mosaics to create below and above waterline data sets.

OceanGate and BlueView determined that mounting the 3D sonar on a manned submersible would be most effective, as scuba divers and ROVs faced multiple monetary and logistical drawbacks to deep-scanning work. Neither approach offers the same visibility or depth rating as Antipodes. The submersible, with its twin large hemispherical acrylic domes, increases situational awareness during scanning operations and enhances versatility by combining with other data-gathering efforts. Antipodes has logged more than 1,250 dives in a variety of sea conditions.

In mid-2010, OceanGate began the process of integrating the BV5000 into its manned submersible operations via a three-phased approach.

Integration Process
In the first phase, OceanGate participated in an Institute of Nautical Archaeology-led expedition to create a 3D scan of the AJ Goddard, a 110-year-old sternwheeler shipwreck that sank during a late October storm in 1901 during the Klondike Gold Rush. In this expedition, scuba divers utilized a higher-resolution, short-range (10 meters), 2.25-megahertz sonar head, the BV5000-2250, to take 3D imagery of the 20-meter wreck that rests upright at the bottom of Lake LaBarge in Yukon, Canada. The expedition captured 20 individual scans during two days of the eight-day expedition. Due to the low-visibility conditions, the resulting 3D images proved to be valuable to the researchers studying and cataloging the shipwreck.

In the second phase, OceanGate began integrating the BV5000 into Antipodes and conducted test dives and shipwreck scans of the SS Al-Ind-Esk-A-Sea, a 110-meter fish-processing vessel near Everett, Washington, and the SS Governor, a 140-meter cruise liner near Port Townsend, Washington. Both wrecks lay in low-visibility waters at depths of approximately 70 to 80 meters, with the Governor site experiencing high and unpredictable currents.

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Stockton Rush is OceanGate's co-founder and CEO. He is also the chairman of Remote Control Technology (Kirkland, Washington) and a member of BlueView Technologies Inc. (Seattle, Washington) board of directors. He obtained his bachelor's in aerospace engineering from Princeton University and his master's from the University of California Berkeley Hass School of Business.

Guillermo S&ohnlein is OceanGate's co-founder and chief operating officer. He is also founder and chairman of the Sea-Space Initiative, and chairman of the Marine Technology Society's Ocean Exploration Committee. He earned a bachelor's in economics from the University of California at Berkeley and a law degree from the University of California Hastings College of the Law.

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