An inertial navigation system (INS) typically consists of an inertial measurement unit (IMU) with two or three accelerometers and three gyroscopes, a computational system to perform the calculations indicated, and additional sensors to improve long‐term navigation performance.
Since the system does not depend on any external signals or references, it will work in a cave, or underwater, or in the fog. It is difficult for mother nature, or a malevolent actor, to significantly degrade its accuracy. The systematic and random errors in the measurement of acceleration and rotation accumulate, however, causing position and orientation accuracy to degrade with time. For example, an INS used for commercial or military aircraft navigation will typically have a position uncertainty of approximately 1 nautical mile, or about 1.7 km in an hour.
In this chapter, the principles of operation and typical characteristics of accelerometers and gyroscopes commonly used in INSs will be reviewed. We start the chapter with an overview of INS error characteristics and performance classes. An overview of inertial technology advances over the last 60 years will then be presented to provide context for the instrument technology discussion. In addition, we will discuss emerging technologies that have the promise of providing even higher‐performance instruments for the next generations of inertial systems.