US Patent 9442564 Motion sensor-based head location estimation and updating

A device that operates a user interface (UI) that depends on the position of the user's head. The device estimates the head position using motion sensors. The device establishes an initial estimated position of the head and tracks the device's movement from an initial reference position to determine the new position of the head. If the head crosses a position threshold the device may partially re-center the head to avoid large errors.