Published online by Cambridge University Press: 23 November 2009
Acoustic transponders are employed in underwater navigation in situations in which a high degree of accuracy is required. Typical applications include underwater search, mapping, photography by a submersible or a towed vehicle and positioning of underwater work systems. The network of transponders, of which there may be only two or three, or which may be very extensive, is implanted by a support ship or by a submersible. The network can be located geographically by a satellite navigation equipment to an accuracy of 0·25 nm. This accuracy (or even accuracy within ± 1 mile) is sufficient to locate the network after a period of disuse. Acoustic navigation of a vehicle is accomplished relative to the network, to accuracies of the order of several feet.