What is an Inertial Navigation System?

Inertial Navigation System Composition

An inertial navigation system provides roll, pitch, heading, position, and velocity.

An Inertial Navigation System (INS) combines:

  • an Inertial Measurement Unit (IMU) composed of 3 accelerometers, 3 gyroscopes – depending on the heading requirement – 3 magnetometers.
  • an internal or external GNSS receiver for Navigation data and velocity, with two antennas for heading in low dynamics applications
  • a micro-processor that runs an enhanced on-board Extended Kalman Filter (EKF) to fuse in real-time inertial data with GNSS and other aiding information (odometer, dvl, etc.).
  • an internal data logger if the system data are to be used after operation (surveying applications for example)

 

An accelerometer measures proper acceleration. This is the acceleration it experiences relative to free-fall, and the acceleration felt by people and objects. Put another way, at any point in space-time the equivalence principle guarantees the existence of a local inertial frame, and an accelerometer measures the acceleration relative to that frame. Such accelerations are popularly measured in terms of g-force, or more precisely in terms of m/s².

 

What is a gyroscope?

A Gyroscope is a physical sensor that detects and measures the angular motion of an object relative to an inertial reference frame. It measures the absolute motion of an object without any external infrastructure or reference signal.

 

What is a magnetometer?

A magnetometer is a measuring sensor used to measure the strength or direction of magnetic fields in order to provide bearing.

 

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