Nautical Archaeology

To search for objects underwater, nautical archaeologists now employ robots and improved sonar technology. These methods were employed to excavate the Titanic, an "indestructible" ocean vessel than sank in 1912. To search for the Titanic, an American-French team employed three robots: Alvin, Angus, and Argo. Alvin was a midget submarine that could descend to the 13 ft (4 m) depth where the ship lay buried. The photographic craft Angus and the television camera craft Argo assisted in pinpointing the location of the Titanic.

During the Titanic mission, the French researchers used a new kind of sonar known as side-scanning sonar. Ordinary sonar surveys a narrow field that must be carefully mapped out in advance. Side-scanning sonar eliminates this drawback, by picking up signals at a diagonal.