|The manipulation of deep-sea cameras|
Hersey, J.B. (1967). The manipulation of deep-sea cameras, in: Hersey, J.B. (Ed.) Deep-sea photography. pp. 55-67
In: Hersey, J.B. (Ed.) (1967). Deep-sea photography. The John Hopkins Oceanographic Studies, 3. The John Hopkins Press: Baltimore. 310 pp., more
In: The John Hopkins Oceanographic Studies. ISSN 0271-2229, more
Deep-sea cameras are remotely manipulated either by suspending them on a long cable or by mounting them on a free submersible. Suspended cameras have been fitted with mechanical, optical, or acoustical sensing devices for their control. This chapter is mainly concerned with acoustical devices; mechanical and optical devices are discussed in other chapters of this book. Acoustic echo-location systems have proven successful in locating and photographing free-swimming fishes at shallow depth in the sea, but the development of these systems, not now actively pursued, occurred at a time when long electrical suspension cables were not available. The technique continues to be promising but it may not be competitive with the use ot free, manned submersibles. Sea-floor photography has used acoustical controls, variants of echo-sounding techniques, and one device which employed a mechanical bottorn sensor to switch off an acoustic signal telling the operator thereby that the camera was the required distance from the bottorn. The most used control is the sound-pulse generator attached to the camera. This radiates one short sound ping per second during a camera lowering, and the difference in time of arrival of this ping and its bottom echo is a measure of the height of the camera above bottom. Display of the acoustic data on a graphic recorder is required both to identify weak signals in noise and to facilitate interpretation of the echoes. Using such controls thousands of photographs of the sea floor have been made, from where the bottom was smooth and flat to the other extreme on the sides of rugged sea mounts and oceanic islands. Continuous coverage of a strip along the bottom over a kilometer long has been developed as a technique and has been used not only for geological reconnaissance but also for deliberate search as in the well-known search for the wreck of the submarine Thresher.