Positioning and navigation under the sea: An acoustic method

Under consideration are the twin problems of transponder positioning and transponder navigation. Unlike other techniques, the present method remains valid even when a single omnidirectional system aboard ship queries and receives replies from a single transponder, either for ship navigation or for transponder positioning. The method uses the Kalman filter approach for real-time processing of the range data between ship and transponder. This processing scheme extracts the needed information in an efficient way from the range data, when the latter is corrupted by random errors due to the effective sound velocity used, to the measurement of the time delay, and to the motion of the querying ship. The method has been evaluated by a Monte Carlo simulation, where the transponder´s R, R_x-R_y coordinates relative to the ship has been estimated. Representative ensemble means and respective rms values for the noise in the range data were treated. For each statistical measure of the noise, one hundred runs were processed by the filter; the errors in the estimated means of transponder´s range, and R_x-R_y coordinates, and their respective rms values were calculated over the one hundred member ensemble at each tenth estimate of the filter output. A performance index was calculated which showed a marked improvement in the estimation when the filter was used. The principal advantages of the presented method are its operational simplicity and reduced cost of its implementation.