The submarine-cable depthometer

THE PROBLEM of plowing submarine cables into the ground or sand making up the bottom of the ocean requires a means of checking the depth of burial of the cable after the plowing operation has been completed. Measuring the actual depth in inches below the surface of the ground is the purpose of a magnetic detecting and measuring device known as the cable depthometer. This magnetic detector is contained in a sled as shown in figure 1, designed for towing by the cable ship along the ocean bottom. The detecting operation utilizes the fact that ocean cables have a protective sheath of iron or steel wires around the copper core and the insulation. The magnetic field arising from the magnetization of the cable sheath, together with the distortion created in the earth´s magnetic field by the cable sheath, generates an electromotive force in detecting coils in the sled, when these coils are moved in a substantially horizontal plane through such a field.