Summary: Navy Instructional film explaining aspects of hydrographic survey, shot onboard the Hecla Class deep ocean survey ship HMS Hecate (A.137). The film includes mention of Decca, Loran, magnetometers and gravitometers. There is particular emphasis on the ship's computer, used to collate various sources of information and provide an accurate plot of the received data. The inputting of data into the computer is covered in some detail. The Sea Cadet Training Ship TS Royalist also appears, demonstrating older methods of ocean survey.
