An Inertial Measurement Unit (IMU) is at the core of all inertial systems.

The IMU degrees of freedom typically reflects the number of sensors axes :

  • 3 DOF for a gyro triad
  • 6 DOF for a full IMU with 3 accelerometers and 3 gyroscopes

IMUs including magnetometers sometime are advertised as 9 degrees of freedom, by counting the magnetic measurements as well. However, in a practical situation, the magnetic field is directly linked to the device's orientation, so 6 DoF still stand for an IMU with magnetometers.

For optimal performance, a temperature sensor is also required if a temperature calibration is applied in the IMU.


In this section, you will learn more details about these sensors and the MEMS technology.