University of Texas at Austin

Tuesday, August 17, 2010

Texas researchers on the hunt for Lake Huron shipwrecks

Sonar mounted on the nose (left end) of the autonomous underwater vehicle will find unidentified shipwrecks at the bottom of Thunder Bay.

Sonar mounted on the nose (left end) of the autonomous underwater vehicle will find unidentified shipwrecks at the bottom of Thunder Bay.

A group of researchers at the Applied Research Laboratories at the The University of Texas at Austin (ARL:UT) are cruising the Thunder Bay Maritime Sanctuary on Lake Huron, mapping the lake-floor for undiscovered shipwrecks and a prehistoric archeological site.

They are deploying an ARL:UT-developed sonar device, the Autonomous Topographic Large Area Survey (ATLAS) sonar, to gather high quality images of the lake bottom and the objects down there.

The survey is of the 448-square-mile Thunder Bay National Maritime Sanctuary, considered one of the nation’s most historically significant collections of shipwrecks.

Thunder Bay is off the northeast side of Michigan’s lower peninsula and is administered by the National Oceanic and Atmospheric Administration (NOAA).

Members of the team have posted information about the project —including videos and sonar images—at a NOAA Web site, Ocean Explorers. And read about the project log.

The 448-square-mile sanctuary contains 40 known shipwrecks, according to NOAA. Another 80 known sites are just outside the sanctuary’s boundaries. Archival research indicates that as many as 100 sites still await discovery in northern Lake Huron.

The ARL:UT ATLAS survey will note known shipwrecks, identify ones not previously known and map the topography of the lake bottom.

ARL:UT has been a pioneer and leader in developing underwater sonar devices since it was founded after World War II. One of its first projects was sonar to identify underwater mines.

The ATLAS is a forward-looking sonar sensor rather than the more traditional side-looking sonar. The sonar’s wide sector enables it to survey a swath up to 1,000 meters wide, which is 10 times the width of a more traditional side-looking imaging sonar.

This map shows where Thunder Bay is and where the area being searched by the ATLAS project.

This map shows where Thunder Bay is and where the area being searched by the ATLAS project.

The sonar is integrated into the nose of a 12-foot-long, free-swimming autonomous underwater vehicle (AUV). The AUV runs tracks back and forth along the lake bottom (like a mower cuts a lawn) as it images the lake-floor along its path.

Watch a video of an AUV launch.

At the end of each day’s mission, the AUV returns to its support craft where it is brought onboard. (Watch a video of a recovery.) The ARL:UT team uploads the sonar data to process and form lake bottom imagery and bathymetry maps (which show the depth) that can be reviewed to identify objects.

In addition to providing the Thunder Bay Sanctuary with maps of a large part of its sanctuary, the project will help assess how well these types of sensors and autonomous vehicles can be used to survey areas of the ocean or lake bottoms.

During the project, the team will also explore a portion of the Alpena-Amberley Ridge, a now submerged land bridge that extends across Lake Huron.

Nearly 10,000 years ago, it connected what is now northern Michigan and Canada. Researchers from the University of Michigan’s Museum of Anthropology have been searching the ridge for prehistoric caribou hunting sites. The ARL:UT team will deploy the ATLAS AUV and survey the ridge to determine its capability to identify remnants of prehistoric human activity.

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