Remembering The Battle Of The Atlantic: Dynamic Underwater Laser Scanning Of A WWII Battlefield

By: Kelci Martinsen, 2G Robotics Inc.

3D Model of German U-576. Photo credit: NOAA and 2G Robotics.

When thinking about the naval battles of the Second World War, the eastern coast of North America is not often the first battlefield to come to mind. However, crucial struggles over supplies were regularly taking place in the Atlantic. Sustained resources were critical to ensure an allied victory, without them, the allied forces in Europe would become increasingly ineffective, succumbing to a war of attrition.

One such conflict took place on 14 July 1942 approximately 35 miles offshore from Cape Hatteras, North Carolina. The German submarine, U-576, was returning home after sustaining damage to the main ballast tank from enemy depth charges. However, U-576 encountered convoy KS-520 consisting of 19 merchant vessels and five military escorts travelling from Norfolk, Virginia to Key West, Florida for an extremely vital resource—fuel.

ULS-500 PRO underwater laser scanner and submersible ready for deployment. Photo credit: NOAA and 2G Robotics.

The German submarine fired four torpedoes into the convoy, damaging a steam merchant and a tanker and sinking the freighter Bluefields. As the U-boat surfaced, Unicoi opened fire on the submarine, landing a successful blow. Meanwhile, Bluefields crew members quickly evacuated the steadily sinking ship. Minutes later, depth charges were released from two U.S. Navy aircraft, sending U-576 to its final resting place on the ocean bed. The entire submarine crew, consisting of 45 men, was lost and four allied crew members were badly injured.

Decades later, U-576 and Bluefields lay forgotten off the coast of North Carolina in approximately 800 feet of water—that is until the battlefield was rediscovered by NOAA. Due to the depth, NOAA was only able to document the sites via a Triton 1000/2 two-person submersible and so turned to a trusted collaborator, 2G Robotics, for an effective way to understand the newly identified battlefield. The submersible was equipped with Sonardyne’s SPRINT INS and 2G Robotics’ most advanced underwater laser scanner, the ULS-500 PRO, to dynamically capture true-scale 3D models of the sites. Even in adverse weather, NOAA’s team was able to complete multiple passes over the 65- and 80-meter baselines. The team diligently photographed U-576 and Bluefields as they passed over, capturing the magnitude of the battle’s carnage. The gaping void in Bluefields’ port side further emphasized the violence of the conflict. Meanwhile, raw laser point cloud data and navigational data were recorded and processed through EIVA navigational software, providing real-time display of data without the use of stitching. As the data for U-576 waterfalled in, it was plain to see the submarine had sustained little exterior damage and the hatches were still sealed tightly, giving additional insight into the last moments of the ill-fated crew members.

Manned submersible inspecting U-576. Photo credit: NOAA.

The data and 3D models captured by 2G’s ULS-500 PRO provided NOAA with a complete millimetric record of the artifacts and site integrity, allowing for precise measurements and improved analysis. NOAA will now be able to monitor site changes over time, particularly those transformations caused by human impact.

The project represents a significant step forward, not only for cultural resource management and in understanding the implications of WWII naval conflicts but also for public outreach. Maritime history is now more accessible, enabling anyone to experience 3D models of U-576 and Bluefields using a virtual reality system, further establishing underwater laser scanners as the new standard for underwater archaeological surveying.

3D model of Bluefields showing extensive damage. Photo credit: NOAA and 2G Robotics.

For more information on the project visit www.2GRobotics.com or http://oceanexplorer.noaa.gov/explorations/16battlefield/welcome.html.