Inertial navigation system (INS), also known as inertial reference system, is an autonomous navigation system that does not rely on external information or radiate energy to the outside (such as radio navigation). Its working environment includes not only air and ground, but also underwater. The basic working principle of inertial navigation is based on Newton's law of mechanics. By measuring the acceleration of the carrier in the inertial reference system, integrating it with time, and transforming it into the navigation coordinate system, we can get the information such as speed, yaw angle and position in the navigation coordinate system.

Inertial navigation system belongs to the reckoning navigation mode, that is, the position of the next point is calculated from the position of a known point according to the continuously measured heading angle and speed of the moving body, so the current position of the moving body can be continuously measured. The gyroscope in the inertial navigation system is used to form a navigation coordinate system to stabilize the measurement axis of the accelerometer in the coordinate system, and give the heading and attitude angle; The accelerometer is used to measure the acceleration of a moving body. The velocity can be obtained by one-time integration of time, and the displacement can be obtained by one-time integration of velocity.
There are several common modern navigation technologies, including astronomical navigation, inertial navigation, satellite navigation, radio navigation, etc. among them, only inertial navigation is autonomous, which neither radiates things to the outside world, nor looks at the stars in the sky or receives external signals. Its invisibility is the best.

Inertial navigation is not as "unreliable" as we think. Many strategic and tactical weapons of the country, such as intercontinental civil aviation aircraft, must rely on inertial navigation system or the combination of inertial navigation system and other types of navigation systems. Its cost is also relatively expensive. For example, an inertial navigation system with navigation level (i.e. one hour error of one nautical mile) needs at least hundreds of thousands, and this precision navigation system is enough to be equipped on aircraft such as Boeing 747. Now, with the progress of MEMS (micro electro mechanical system) inertial device technology, commercial and consumer inertial navigation has gradually entered the homes of ordinary people [1].