Method
Exploring the deep
Search Vessel - The Northern Horizon
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How do you find a wreck that's some 3,000 metres under the sea? At that depth, as well as being dark and cold, the pressure is very high. Apart from the occasional fish it is barren. No human being could survive the extreme conditions of this underwater desert.
The only way to explore the sea bed at such depths is by using equipment controlled from a ship at the surface. David Mearns of Blue Water Recovery led the expedition to find out what happened in the epic battle between the German ship, Bismarck and the British ship, Hood. He had at his command the latest technology. First, though, he and his team had to undertake months of research.
Before setting off
The team started by finding out everything they could about the vessel and what happened on the day she went down. They used historical records, such as logbooks of every ship and reports from every aircraft that were in the vicinity of the battle, as well as photographs, eyewitness reports and any other material that related to the event. In this way they built up a picture of the position of the ship and how she sank.
They needed to find out what conditions they would face at the exploration site. Researching the weather, winds, currents and the geography of the sea bed, they discovered that there was just one period of a few months in the year when it was feasible for the expedition to go ahead.
The team analysed every piece of information. They needed to decide whether the data was reliable: was the witness an inexperienced member of the crew or a long-serving sailor? How accurate were the ships' instruments and what was the margin of error?
Finally, they had enough information to reconstruct the positions and movements of all the ships and planes in the vicinity of the battle on 24th May 1941. This gave them a reasonable idea where the wreck may be.
Plan of action
Side Scan Sonar - Explorer 6000
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The next stage was to develop a search plan and gather together the sophisticated equipment they needed.
David Mearns' team identified an area of 600 square nautical miles within which they expected to find the wreck. This was a massive area to search, but their state-of-the-art side scan sonar mounted on a remotely operated vehicle (ROV) searched the site, in an action they call 'mowing the lawn' until it found the ship. All the time, the sonar sent signals back to their survey ship, where computers translated them into images.
Also mounted on the ROV were specialised cameras that can function as deep as 6,000 metres, and lights adapted to enable the cameras to take high quality pictures in these dark conditions. In turn, these pictures were sent along a fibreoptic cable to the survey ship so the explorers could see exactly what the ROV found, 3,000 metres down.
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