An inertial guidance system (also known as an inertial navigation system) uses gyroscopes, accelerometers, and computers to calculate the position, velocity, and attitude of a vehicle in motion. An inertial guidance system electronically samples the current placement and acceleration of a vehicle on a continuous basis to determine its future course. Gyroscopes, often three, furnish information on fixed reference directions. Accelerometers monitors velocity changes. Computers process the data from the gyroscopes and accelerometers, ensuring the vehicle is on course. The system is self-contained and supplies navigational information without communicating with a satellite or base station. Inertial guidance systems have been used on airplanes, submarines, and missiles since the 1970s in the United States.

There are several kinds of inertial guidance systems, the gimbaled inertial system and the strap-down inertial system, with the former the more common. The gimbaled inertial system has up to four...