Localising divers or equipment near offshore structures - using mathematical appts. to deduce coordinates from times taken for signals to travel from position to transducers (BR 13.6.78)

摘要

A method of localising divers or under-water equipment in a space in which there are obstacles, partic. near an off-shore structure comprising columns, consists of placing three transducers in a horizontal reference plane and a fourth transducer outside this plane, defining a second reference plane. The diver, or the equipment, is supplied with an emitter. Th times taken for signals from the emitter to reach the transducers are treated by a mathematical appts. which allows the co-ordinates of the diver or equipment to be deduced, as a function of the speed of sound in the medium and of the distance between the transducers. The values of the elements of the projection on the planes of reference of the triangles formed by the four transducers and the emitter are determined. A group of two adjacent triangles defined by three transducers and the emitter defines a coordinate element. Ageing of off-shore petroleum installations demands more supervision as the equipment becomes older. Process solves problems posed when these controls have to be carried out at great depth, over 100m. and in poor visibility, where existing methods are not applicable.