Orientation Sensing

Accelerometers - Detect linear acceleration of devices along the x, y and z axis
Gyroscopes - Detect angular velocity i.e. speed at which a device is rotating along the x, y and or z axis
Both accelerometers and gyroscopes usually found inside an Inertial Measurement Unit (IMU)
Magnetometer - relies on the Earth's magnetic field to determine the host's object's orientation related to the Earth's Magnetic North
When combined with accelerometers and gyroscopes, can stabilize orientation calculations, and determine orientation w.r.t earth

Accelerometers can detect the force of gravity by detecting the acceleration due to gravity along its different axes
- By itself it can measure pitch and roll (tilt) rotations but cannot measure yaw
Gyroscope can measure roll, pitch and yaw by integrating its values
- However, Gyroscopes are prone to drift, which is why data is fused with accelerometer
- Since accelerometer can't measure yaw, this value will drift still
- By fusing with magnetometer, yaw drift will stop
- Some gyroscopes have 'self-correction' feature

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