An
inertial navigation system (
INS) is a
navigation aid that uses a
computer, motion sensors (
accelerometers) and rotation sensors (
gyroscopes) to continuously calculate via
dead reckoning the position, orientation, and
velocity (direction and speed of movement) of a moving object without the need for external references. It is used on vehicles such as
ships,
aircraft,
submarines,
guided missiles, and
spacecraft. Other terms used to refer to inertial navigation systems or closely related devices include
inertial guidance system,
inertial instrument,
inertial measurement units (IMU) and many other variations. Older INS systems generally used an
inertial platform as their mounting point to the vehicle, and the terms are sometimes considered synonymous.