What is INS?
INS is an acronym for Inertial Navigation System. It is a navigation device that uses accelerometers, gyroscopes and microcomputers that process information in real time, and continuously calculates the position, orientation and speed of objects through dead reckoning.
Inertial sensors are often supplemented by barometric altimeters and sometimes magnetometers or velocity measuring devices to measure magnetic fields in three dimensions. Nowadays, most INS systems output heading, pitch and roll. It can be used in transportation such as ships, airplanes, submarines and spacecraft.
What are its components?
Inertial navigation systems mainly consist of accelerometers, gyroscopes, and computers that process information from motion sensors.
Gyroscopes are used to measure the angular velocity of the sensor frame relative to the inertial frame. Accelerometers provide information about the velocity and direction of acceleration based on measurements of the vehicle's linear acceleration relative to itself. Together with linear acceleration, angular velocity provides accurate information on all position changes of a moving vehicle. These motion sensors are at the heart of inertial navigation systems, known as inertial measurement units (IMUs). Typically three gyroscopes and three accelerometers are included. Some IMUs are also equipped with a magnetometer for enhanced functionality. The computer synthesizes all the information by combining the data gathered from the motion sensors to calculate the current position of the vehicle.
How does it work?
What makes an inertial navigation system such a useful navigation solution is that it can calculate the position, direction and velocity of moving objects without the need for GPS technology.
The INS device operates on a dead reckoning system, meaning that the vehicle's initial position, velocity, and orientation are provided by an external source, which can be a GPS satellite receiver or an operator. With this data, the INS can start calculating position, velocity, and other elements of motion. As the vehicle continues to move, the INS will calculate and update all motion elements by itself with information received from the motion sensors.
What’s the difference between an IMU and an INS?
①IMU is a combination of multiple accelerometer and gyroscope axes. Traditionally, IMUs consist of accelerometers and gyroscopes to measure absolute spatial displacement. In contrast, an INS is a system that integrates an IMU with GPS/GNSS/GLONASS chips and computing skills. The IMU (inertial measurement unit) is essentially the sensor subsystem of the INS (inertial navigation system).
②INS gets the raw output from the IMU and calculates changes in the relative motion of the object. The INS references these changes to a known origin, velocity and direction, providing real-time position and vector output.