Abstract: 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.

Abstract: A method of measuring attitudes and position of an underwater system by a navigation processor on board a vessel, as well as such a navigation processor. The method includes i. receiving a position of the vessel based on data from a DGPS surface position equipment on board said vessel, ii. receiving data from a fiber optic gyrocompass on board said underwater system, the gyrocompass including heave, roll and pitch sensors, iii. receiving depth data of the underwater system, iv. receiving velocity data of the underwater system, v. receiving range and bearing data of the underwater system, in order to calculate attitudes and absolute coordinates of the underwater system in a first coordinate system that is a common coordinate system.

Abstract: Arrangement with an acoustic array with a sound velocity meter, suitable to be arranged under water. The acoustic array is able to receive acoustic signals from an underwater device and to provide acoustic array output data to a processing arrangement such that the processing arrangement can perform in real-time, a calculation of a position of the underwater device relative to the acoustic array based on the acoustic array output data. The sound velocity meter is able to measure velocity of sound in fluid layers just below a vessel floating on the water and to provide sound velocity meter output data to the processing arrangement such that the processing arrangement can correct the calculation of the position of the underwater device based on the sound velocity meter output data in real-time.