Getting a high-res look at shipwrecks

A crew from the National Oceanic and Atmospheric Administration was in Port Washington on the 80-foot research vessel Laurentian for the last week, but their mission wasn’t on the surface of Lake Michigan.

They were looking deeper, using advanced technology to get an up-close view of shipwrecks in the area — images so sharp and clear that you can see the wood grain in what’s left of the wrecks, Brad Hibbard of Hibbard Inshore, a Michigan firm working with NOAA on the project, said.

“The level of detail is amazing,” Hibbard said. “You can see the wood grain. You can see the size of the mussels on the wrecks. Some wrecks, you can make assumptions what it is, but with this technology you know for sure.”

The detail is also important because the wrecks are degrading, Caitlin Zant, maritime archaeologist and research coordinator for the Wisconsin Shipwreck Coast National Marine Sanctuary, said.

“This gives us a baseline for future studies,” she said. 

Zant said the technology was being used primarily on some of the deep-water wrecks, such as the Senator, which is in 415 feet of water.

“They’ve been imaged but not in incredibly high detail,” she said.  

The work done this past week is “proof of concept,” Russ Green, the sanctuary superintendent, said.

“We’re looking at the underwater technology and how to apply it,” he said.

The sanctuary received a grant to fund the work, which in Port was being used to look at several wrecks, including the Senator, the Northerner and the St. Peter, and to get an up-close look at depressions on the bottom of the lake.

They are using technology, including sonar, a laser scanner, lighting and cameras, mounted on an autonomous underwater vehicle, or AUV.

“The lights are really important,” Green said, noting it allows them to get crisp, color images.  

“Wood looks like wood. Mussels look like mussels,” he said.

  The AUV is from Hibbard’s Michigan-based company, which specializes in using unmanned and remotely controlled vehicles to inspect underwater infrastructure. He said he and his crew jumped at the chance to work on this project.

“These are exciting new things to learn about,” Hibbard said. “Honestly, shipwrecks are more interesting than infrastructure.”

The AUV can be operated fully autonomously or a cable can be attached to it and a pilot on the ship can direct it.

“The flexibility gives us more options,” Hibbard said, something that’s important when dealing with the depth of some of the wrecks.

The AUV can provide an overview of the wrecks using sonar and more detailed, close-up images using optical imaging, he said.

For deep-water wrecks, the vehicles are the best means of getting images, Green noted.

“Unlike a diver, this has unlimited time it can stay under water,” he said. “Over 100 feet, diving (time) is restricted. The amount of time you have at the bottom is five to 10 minutes.”   

Hibbard said the machine can also get to and from the wrecks much more quickly than divers, who make their way slowly.

“It takes a matter of minutes to get to 450 feet,” he said, adding their first pass of the Northerner took only seven minutes.

“We’re taking days of surveying down to hours,” Hibbard said, adding the AUV also allows them to get “very close and very precise.”

To ensure they don’t damage the wrecks, he added, the AUV is equipped with an anti-collision system.

The initial passes of the wrecks are to get an overview of the site, Hibbard noted, with subsequent passes used to provide  more detail.

The AUV can also geolocate what it finds, Hibbard said, allowing them to accurately map the wrecks.

For example, he said, when looking at the Northerner, they found a piece of the mast “a ways away” from the rest of the ship.

“We’re going to be imaging beyond the wrecks, out to the sides,” he said.

The technology is being used to study wrecks, not to find them, Green said, as well as to examine the depressions found in the bottom of the lake.

Those depressions, Zant said, are most likely remnants of the last glacial retreat, noting some of their features are similar to those found in fjords in Norway.

Green said that the crew hopes to return to Port next year to continue its studies of the wrecks.

“There’s a lot to be learned out here,” he said.