Inertial navigation is a technique using a self-contained system to measure a vehicle’s movement and determine how far it has moved from its starting point. Acceleration is a vector quantity involving magnitude and direction. A single accelerometer measures magnitude but not direction. Typically, it measures the component of acceleration along a predetermined line or direction. œe direction information is usually supplied by gyroscopes that provide a reference frame for the accelerometers. Unlike other positional methods that rely on external references, an INS is compact and self-contained, as it is not required to communicate to any other stations or other references. œis property enables the cra£ to navigate in an unknown territory.