2016 Andrea Doria Expedition
The primary objective of the Andrea Doria Expedition is to capture 2D and 3D sonar images of the shipwreck to document its current condition. The team will attempt to establish reliable baseline data of the wreck so explorers and scientists can better assess its decay over time.
This iconic shipwreck has been explored by scuba divers and mixed-gas divers for decades – with the first dive occurring within hours of the sinking. These dives have resulted in limited views of the wreck due to the short bottom time available to divers (approx 20 minutes per dive) and limited visibility.
Because divers can only spend a few minutes at this depth and because water turbidity limits visibility to a few dozen feet, it is nearly impossible for divers to capture images of the full scope of this 697 foot long shipwreck. Divers just cannot spend enough time or see well enough to fully view the wreck. Plus, as the ship decays, the familiar shipwreck landmarks that divers use to navigate around the vessel are changing or disappearing. As a result there are no images that fully illustrate the scope of the wreck in its current state.
The 2016 Andrea Doria Expedition will attempt to change the current state of knowledge of the wreck with sonar scans from aboard a manned submersible. The team will attempt to systematically image the vessel and debris field immediately around the wreck, including:
- 3D sonar scans that may be assembled into a virtual model of the wreck
- 2D downward looking sonar video of the length ship as the submersible does a ‘fly-over’ to perform multiple transects
- 2D sonar with a range of up to 100 meters and can capture images of objects as small as 1″
- Video and photographs of the wreck and artifacts
Andrea Doria sank about 50 miles south of Nantucket at: 40° 29.416N / 69° 51.996W
How Do We Create 3D Images Under Water?
To create a single scanned image, the submersible takes up position on the seabed about 15 meters from the wreck and remains stationary for about 5 minutes. The sonar head rotates on a vertical axis through a 180-degree arc as shown in the illustration. The sonar sends out a 900MHz sound wave and records the echoes as XYZ point cloud data in virtual 3D space. Once the scan is complete the submersible moves to its next assigned position for the adjacent scan and repeats the process. The individual scans are then digitally assembled to create a model – a process very similar to creating a single panoramic image from multiple photographs – using overlapping data in adjacent files to align the images.
To construct a 3D model of a shipwreck, the submersible is repositioned around the wreck to create a series of scans with overlapping elements.
3D scan of the AJ Goddard, a Klondike gold rush era paddle wheeler that sank in Lake Lebarge in the Yukon Territory. The black circles are the center of individual sonar scans.