Sensors inside the plastic device measure acceleration rates to determine whether a blow in rugby or other contact sport could induce brain injury.

Many driverless car plans now involve visual navigation, identifying landmarks with lasers or cameras, as well as inertial systems that can measure acceleration, deceleration and turning to estimate position.

Three orthogonal gyroscopes establish an inertial reference frame, and the accelerators measure acceleration relative to that frame.

Accelerometers, which measure acceleration of the vibration, can also be used.

It measures acceleration instead of velocity of ground movement.