Inertial Navigation Systems and How They Work

hand holding compassWhen the word "navigation" is mentioned, most people think about ships and airplanes and how they find their way around the world. For the layman, that's exactly what it means. But for those who are in the marine or aviation industry, navigation is more than just knowing how to use a compass. There are terms like GPS, long-range navigation, radar, and gyrocompass that all contribute to a vessel's need for large-scale navigation. INS simulation, inertial instruments, and measurement units also have a role to play in aviation and marine navigation.

What is Inertial Navigation?

Inertial Navigation is a technique that uses measurements from navigational sensors to determine the velocity, orientation, and position of a moving object. An inertial navigation system doesn't need external references and will continuously provide these calculations without requiring communication from any station. It uses a computer, and rotation, motion, and magnetic sensors to constantly calculate the result. It is used in the navigation of ships, submarines, spacecraft, and missiles.

The Inertial Measurement Unit (IMU)

This unit is composed of accelerometers and gyroscopes that are all held together so that not one of its parts moves. This is called a strap-down system, making its readings more reliable and less prone to failure. In an IMU, the gyroscope doesn't use a fast-rotating object. Instead, it uses the interference of electromagnetic beams to measure rotation.

The Role of Software

Velocity and position can't be measured by the IMU alone. They are calculated by using a software that adds changes in velocity to an initial velocity, or all changes in position to an initial position. Inaccuracies are solved within the software using a smoothing filter that identifies a mismatched position and velocity measurement. 


An INS requires high-quality engineering and training for it to produce accurate results. While the extreme accuracy of the gyroscopes makes the system expensive, the investment is worth it as it provides accurate and reliable results even when measurements are not available.