A system to control a plane or spacecraft; uses inertial forces WordNet 3.0 & Open English WordNet

An inertial navigation system is a navigation device that uses motion sensors, rotation sensors and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity of a moving object without the need for external references. Wikipedia

Navigation aid relying on systems contained within the vehicle to determine location Wikidata

An electronic device that measures a craft's velocity, orientation, and gravitational forces, using a combination of accelerometers and gyroscopes. OmegaWiki