Performance analysis of deep ocean acoustic navigation systems

Two distinct acoustic methods are used to provide precise navigation at sea over areas of approximately 100 km
²
. Both methods position via acoustic transmission from a set of moored transponders or beacons. When the elements of the reference net are operated in a transpond mode the system is called a pulse positioning system; when operated in a continuous mode the system is known as a Doppler system. A combined navigation scheme which capitalizes on the attributes of both the pulse and Doppler modes is under development. It will be capable ultimately of positioning a platform with respect to the reference net with an error of 1 to 2 meters, and of repositioning a platform within 10 cm of a previous fix in 5 km depth water. In this paper we present a performance analysis of the pulse-Doppler system in which we consider the the characteristics of the system receivers in detecting pulse and Doppler informatiorn. Factors affecting performance such as signal level, receiver bandwidth, ambient sea noise and platform motion are discussed. Comparisons are made between optimum and typical performance.