A navigation processor is interfaced to an acoustic processor and to DGPS surface positioning equipment on a vessel. The navigation processor receives (a) position data from the DGPS surface positioning equipment, (b) data from a gyrocompass on an underwater system, (c) depth data of the underwater system, (d) velocity data of the underwater system based on data from a Doppler log unit on board the underwater system, and (e) range and bearing data of the underwater system from the acoustic processor, in order to calculate coordinates of the underwater system.