Today it is difficult to find any form of transport that does not use a GPS navigation system. Submarines are an exception, as GPS does not work underwater. If the submarine was equipped with such a system, then in order to determine its location, it would have to surface every time, which is fraught with inevitable detection.
Accelerometers currently used on submarines are not very accurate. During the day, the deviation from the course can be up to 1 kilometer. The real breakthrough was the creation by a group of British scientists from the Laboratory of Defense Science and Technology under the direction of Neil Stansfield, a device they called the Quantum Accelerometer.
His work was based on studies of the properties of atoms placed with a laser into a vacuum trap, where they were cooled to almost absolute zero (- 273, 15 degrees). In this state, atoms begin to react very sensitively to the slightest disturbances in the external environment. At one time, the authors of these studies were awarded the Nobel Prize in Physics.
The experimental prototype of the device is distinguished by excellent accuracy. The deviation does not exceed 1 meter during the day. The disadvantages of a quantum accelerometer should be attributed, oddly enough, its hypersensitivity, which reacts to the slightest gravitational deviations from acceleration when the submarine moves. A full-fledged three-axis system, consisting of three identical accelerometers, is supposed to be created and tested by next year.