# What an Inertial Navigation Systems

An Inertial Navigation System (INS) is a type of navigation system that uses a combination of accelerometers and gyroscopes to determine the position, velocity, and attitude of a vehicle in real-time. The INS system is self-contained and does not rely on external references such as GPS signals, making it useful in environments where GPS signals are unreliable or unavailable.

The heart of an INS system is an Inertial Measurement Unit (IMU) which is typically made up of 3 accelerometers and 3 gyroscopes. The accelerometers measure the linear acceleration of the vehicle in the x, y and z axes, while the gyroscopes measure the angular velocity of the vehicle in the same axes. These measurements are taken at a high rate, typically several hundred times per second, and are then processed using mathematical algorithms to determine the vehicle’s position, velocity and attitude.

The mathematical algorithms used in INS are mainly based on Kalman filtering, which is a mathematical technique that uses a combination of measurements and predictions to estimate the state of a system. The INS system uses the accelerometer measurements to estimate the velocity and position of the vehicle, while the gyroscopes are used to estimate the attitude of the vehicle. The INS system also uses a process called integration, which is used to compute the position and velocity of the vehicle over time by integrating the accelerometer measurements.

INS systems are widely used in a variety of applications such as aircraft, missiles, ships, and other vehicles that require precise navigation. They are also used in autonomous vehicles and drones, where the ability to navigate without external references is crucial for maintaining stable flight and avoiding collisions. Additionally, INS systems are also used in some land vehicles, for example, for Autonomous vehicles and mining equipment, that require precise navigation in GPS-denied environments.

An INS system is not without limitations, however, as it is affected by errors that accumulate over time and these are called drift errors. To overcome these errors, INS systems are often integrated with other navigation systems such as GPS, which can be used to periodically update the INS solution and reduce the drift errors. This integration is known as a GPS/INS system, which is widely used in many applications today.