Opérations de dragages en mer profonde. Optimisation du traict et détermination des trajectoires grâce aux techniques ultrasonores

During the past ten years, the use of pingers has profoundly modified methods of work on the deep-sea bottom. At first used to localize, in relation to the bottom, instruments dropped vertically from a ship (EDGERTON and COUSTEAU, 1959, EDGERTON, COUSTEAU, HERSEY and BACKUS, 1960, for deep-sea cameras ; NALWALK, HERSEY, REITZL and EDGERTON, 1962, for rocky dredges) pingers have also been used with success to survey the descent of otter trawls (BACKUS 1966) or beam trawls (ROWE and NIENZIES, 1967). In al1 these methods, the pinger essentially gives knowledge of the precise instant of contact with the bottom, and the length of time the dredge or trawl works on it. In general, the assistance of a pinger substantially increases the chance of success in abyssal dredging (see MENZIES, 1964). [NOT CONTROLLED OCR]