inertial navigation

inertial navigation. The determination of (a) position relative to an established starting point, (b) velocity, and (c) heading, by the measurement of accelerations in known space-oriented directions, and processing the data by computer. Inertial navigation is founded on the work of Newton in 1687, Foucault in 1851, and Schuler in 1908.

The system of navigation known as SINS (Ship's Inertial Navigation System), was developed after the Second World War (1939–45) for use in nuclear submarines which remain submerged for prolonged periods. The system must also be completely secure from outside detection. If a submarine's position is accurately plotted at the start of its voyage, and if all subsequent accelerations in their component directions can be measured, they can then be translated by calculation into speeds and distances which, when applied to the initial position, give the present position.

Inertial navigation is in fact an extremely sophisticated and precise method of dead reckoning, using accelerometers. The system can measure every acceleration due to speed and course changes, and can eliminate the effects of gravitational attraction, pitching and rolling, etc. The first major public demonstration of the system accuracy was in 1958 when the US nuclear submarines Nautilus and Skate navigated under the polar ice cap. Since then nuclear submarines have made submerged circumnavigations navigated by SINS. So accurate is the system that a margin of error of not more than 100–200 metres (330–650 ft) is expected after a circumnavigation.

Mike Richey