Using new tech to locate sunken ships

Sensors on unmanned submarines could give researchers more data

Idun Haugan
NTNU Gemini

NTNU

Photo: Norwegian Defense Research Establishment / NTNU Gemini
Pictures 1 and 2 show wrecks depicted with standard side-searching sonar. Picture 3 shows the same wreck depicted with Synthetic Aperture Sonar (SAS).

An estimated three million shipwrecks lie in seabed graveyards around the world—with as many as 1,000 of them around Svalbard.

“The world’s oceans are like a big museum,” says Øyvind Ødegård, a marine archaeologist with 20 years of experience at NTNU who recently defended his dissertation, “Towards Autonomous Operations and Systems in Marine Archaeology.”

“The technological advances that have taken place over the last few years are fantastic. A human diver can only work down to about 30 meters [about 100 feet], and the vast majority of shipwrecks are much deeper than that. Underwater robotics, sensors, robots, and control systems are now making it possible to obtain completely new insights into what’s on the seabed,” he says.

Hunting for the Holy Grail

A ship graveyard lies between Svalbard and Greenland, where there are about 1,000 wrecks. Seventeen of them are located in the Smeerenburg fjord. Ødegård is particularly interested in these ships. “Somewhere down there on the bottom of the ocean are 17 shipwrecks, all in about the same area. That’s the grail I’m hunting for,” he says.

How they all ended up there is a story unto itself. Before people relied on fossil fuels for heat and light, whales were a highly sought-after commodity because of their fat. The northern waters of the Arctic were rich with whales. This drew ships from many nations, in spite of the harsh conditions.

The Netherlands established the first whaling station north of Svalbard, called Smeerenburg. It was nicknamed “Fettbyen” or “Spekkbyen”—Fat town—as whale oil production took off. The intensive hunt managed to almost exterminate whales in the fjords and along the coast in just a few decades.

And so the ships had to venture farther north into more inhospitable waters, which inevitably led to shipwrecks. During one winter, 13 Dutch ships became stuck in drift ice in Sorgfjorden and had to be abandoned. The crew survived, but their ships disappeared into the frigid depths.

It wasn’t only difficult waters that caused shipwrecks, however. The highly prized whale oil and the opportunity to conquer new lands created major conflicts, not least between the Netherlands and France.Two French frigates and 40 Dutch whaling ships battled in 1693 in Sorgfjorden, which led to two ships sinking on the spot. Another 17 Dutch ships were taken back to the Smeerenburg fjord and sunk there. These are the ships that Ødegård seeks.

“We have reason to believe that there are many wrecks in the Arctic that are especially well preserved because of the cold water,” says Ødegård.

Underwater technology advances

Finding them will require the technological innovations that Ødegård and his colleagues have been testing.

Researchers can now use joysticks to control underwater operations with great precision. The control systems are advanced and smart, and artificial intelligence and powerful computers enable robots to evaluate many situations independent of human help.

“We’ve seen huge developments in underwater robotics and relevant sensor technology over the last few years. In my thesis, I looked at how selected platforms and sensors can be used to develop new methods for marine archaeology research with a high degree of autonomy, and I suggest a model for how such decisions can be made without needing a human being in the loop,” Ødegård said.

Smart sensor technology

Three sensor technologies are essential for mapping shipwrecks at great depths and with great precision.

“Synthetic aperture sonar (SAS) technology, which is a high-resolution acoustic sensor developed by the Norwegian Defense Research Establishment and Kongsberg Maritime, has collected data that represents a quantum leap in quality and accuracy, compared to traditional methods,” says Ødegård.

This acoustic sensor produces high-resolution images. Detailed bottom maps can thus provide important information without the need for dives with a video camera to confirm or eliminate possible wreck finds.

Another tool that researchers have used is an underwater hyperspectral imager (UHI). This is an optical sensor that takes photographs using the entire visible light spectrum. Common cameras use only three wavelengths (RGB), whereas a UHI uses up to 800.

Finally, a stereo camera on a remote-controlled underwater robot is used to create high-resolution 3D models of selected wrecks using photogrammetry. The camera provides resolutions down to the millimeter.

The stereo camera is “excellent for documenting and monitoring wrecks, where even small details can be very important,” Ødegård says.

These three sensors, plus others, could be housed on a single underwater vessel. “The long-term goal is to have extended and completely autonomous expeditions with unmanned AUVs, where wrecks can be detected, mapped, and inspected with a variety of sensors and then return to the surface with high quality datasets. We aren’t quite there yet, but we’ve been surprised by how close and how far we’ve come,” Ødegård says.

 
This article originally appeared in the October 5, 2018, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.

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