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Coast Survey’s Vitad Pradith (right) offers instruction on the use of the magnetometer, prior to actual deployment. From left to right are team members Pasquale DeRosa, ship’s captain; John Wagner, maritime archaeologist; and Joseph Hoyt, maritime archaeologist.

How do ocean explorers know where to look when they investigate and document the historical secrets of the deep? Well, archaeological expeditions use a myriad of modern surveying technologies. Recently, when NOAA’s Monitor National Marine Sanctuary was investigating a World War II underwater battlefield site, they called on a surveying expert with NOAA’s Coast Survey to assist.

Vitad Pradith, a physical scientist with Coast Survey’s Navigation Services Division, joined a sanctuary team for a week, to provide ocean depth information for the marine archaeology site off North Carolina’s Outer Banks. Pradith and the sanctuary scientists onboard NOAA National Marine Sanctuary Vessel SRVx combined previous depth soundings with new data acquired by sonar to facilitate safe operations of an autonomous underwater vehicle looking for wreckage in depths exceeding 300 feet.

The team also prepared to follow up on items discovered during the 2011 Battle of the Atlantic Expedition. Pradith trained sanctuary archaeologists to use a magnetometer that will detect metal even if it is buried under the sea floor. With the magnetometer, teams can go back to previous contacts to investigate “items of interest” that were barely distinguishable with sonar. This particular sensor enables scientists to visually map the magnetic fields of the contacts to help discover vessels lost in battle.

COAST SURVEY AND THE ATLANTIC COAST DURING WORLD WAR II

This isn’t the first time that Coast Survey experts are involved in World War II wrecks on the Atlantic Coast. Following the attack on Pearl Harbor, the Coast and Geodetic Survey expanded rapidly and devoted virtually all of its resources to the successful prosecution of the war effort. They provided ships, personnel and, of course, charts.

“At the beginning of WWII, the C&GS annually produced about 800,000 nautical and aeronuatical charts, and related products,” explains Albert ‘Skip’ Theberge, a noted NOAA historian. “The comparable figures for the last year of the war were approximately 23 million publications. These included the normal suite of domestic nautical and aeronautical charts, but then the agency added aeronautical charts of foreign territories, target charts for aerial bombing, and other special charts.”

Two of those special charts, produced by the U.S. Coast and Geodetic Survey in 1942, were classified “restricted” — for purposes of anti-submarine warfare — until they were declassified in 1982. Bottom characteristics were mapped by the Woods Hole Oceanographic Institution for the National Research Defense Committee and overlaid on Coast and Geodetic Survey charts. The sunken ship locations, determined by C&GS, were also noted on the charts. See:

• Cape May to Cape Hatteras, published Sept. 1942, by the U.S. Coast and Geodetic Survey, L.O. Colbert, Director (declassified 2/21/84)
• Cape Hatteras to Charleston Light, published Sept. 1942, by the U.S. Coast and Geodetic Survey, L.O. Colbert, Director (declassified 2/21/84)

Theberge points out that “because of enemy submarine attacks, the Atlantic coast was strewn with shipwrecks that constituted major hazards to navigation. They were also mistaken for potential submarines ‒ thus the need to chart their location both for navigation and defense purposes.”

“In 1943 and 1945, USC&GS surveyors used a primitive sidescan system, coupled with an early marine magnetometer, camera system, and recording fathometer for locating and identifying wrecks,” he says. “The project’s primary objective was to develop methods for anti-submarine warfare but it also served as a model for modern hydrographic search methods.”

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Coast Survey’s Navigation Response Team 4 is conducting a year-long survey of the sea floor in the Port of Houston and Galveston Bay navigational areas, re-measuring ocean depths and searching for dangers to navigation. Coast Survey will use the data to update future nautical charts to help mariners protect lives and increase shipping efficiencies. Recently, the team also found an opportunity where they could support marine archeological preservation.

Last week, the navigation team worked with federal and state partners who help us understand the rich history – and the secrets of human sorrows – lying on the seafloor. In collaboration with NOAA’s Flower Garden Banks National Marine Sanctuary and the Texas Historical Commission’s Marine Archeology Division, the navigation response team — with the State Marine Archeologist onboard —  re-mapped the location of two historically significant wrecks. (Some of the data was collected under an antiquities permit, as Texas requires for investigating historic shipwrecks in state waters.)

“With the often-shifting sediment around here, there are periods of covering and uncovering, so archeologists like to periodically map historically significant wrecks to see what’s changed,” explained Nick Forfinski, the navigation response team’s leader. “We were ‘in the neighborhood,’ surveying for maritime commerce, and we were able to obtain up-to-date images of the wrecks while we were here.”

The steamship City of Waco is one of the historical wrecks that Forfinski’s crew was asked to survey. The steamship burst into flames and sank on Nov. 8, 1875, and 56 people died. The sunken ship was ordered to be demolished in 1900, to protect navigation in the area.

“The collaboration between NOAA experts and the Texas Historical Commission brings a unique combination of expertise and resources to learning more about the hidden history in the Gulf of Mexico,” said Texas State Archeologist Pat Mercado-Allinger. “We are grateful to the NOAA Team for this opportunity to remap this historically important shipwreck.”

Forfinski’s team captured some fascinating images of the City of Waco, created from data they gathered during last week’s hydrographic survey.

This image was created from data acquired by NRT4′s multibeam echo sounder. NOAA hydrographic survey units use multibeam echo sounder systems to acquire full (and partial) bottom bathymetric coverage, to measure depths over critical items such as wrecks, obstructions, and dangers-to-navigation, and for general object detection.

This image was created from data acquired by NRT4’s side scan sonar. A side scan creates a “picture” of the ocean bottom. For example, objects that protrude from the bottom create a light area (strong return) and shadows from these objects are dark areas (little or no return), or vice versa, depending on operator preference.

Using hydrographic surveys for multiple purposes, like “piggybacking” wreck mapping on to a navigation safety project, makes for smart resource sharing. It positions America for the future while helping to preserve its past.