Inertial navigation system (INS) is a system that uses gyroscopes and accelerometers installed on the carrier to determine the position of the carrier. Through the measurement data of gyroscope and accelerometer, the motion of carrier in inertial reference coordinate system can be determined, and the position of carrier in inertial reference coordinate system can also be calculated.           
Different from other types of navigation system, inertial navigation system is completely autonomous. It neither transmits nor receives signals from outside. The inertial navigation system must know the position of the carrier accurately at the beginning of navigation. The inertial measurement value is used to estimate the position change after the start.