World global positioning system (GPS) created in the USA in the late 80-ies, relies in his work on 24 satellites. During this time it has evolved considerably and has become an integral part of our civilization. Thanks to it, users can accurately determine its location and time anywhere in the world – and this is particularly important for the armed forces.
If to speak about the US army, the total dependence of the Pentagon from the GPS makes global positioning system one of the priorities in the risk of major conflict. In the Arsenal of many developed countries already have anti-satellite weapons, GPS jammers and spoofer (devices that mimic GPS signals that contain false information – approx. ed. Techcult.ru).
To insure in case of GPS failure, the us army developed several alternative technologies. One of them proposes to use for the navigation of Navy ships good old sextant (invented in 1730 independently by the Englishman John Hadley and American Thomas Godfrey). Another, more modern and advanced – technology navigation via magnetic anomalies MAGNAV.
The magnetic field that protects the Earth from solar radiation, being comprehensive, and varies depending on the location within it of any object. These variations recorded by magnetometer, can be correlated with a map of the planet. The result is a magnetic map of the Earth that doesn’t need satellites and even a topographical map. According to the publication Defense One, positioning accuracy MAGNAV is 10 meters.
Source — Defense One