Many new computers, and especially mobile phones and tablets, provide hardware support to track their orientation. The HTML 5 specification defines the DeviceOrientation
API to expose this information. Just as with the Geolocation API, OpenLayers provides the ol.DeviceOrientation
class to make it easier to work with this API in a stable, cross-browser compatible way.
Device orientation refers to the orientation of the mobile device relative to a common starting point. A device's orientation is then reported as angles of rotation from this common reference orientation. For mobile devices, the reference orientation is defined as the phone lying face up on a table with the top of the phone pointing north. For computers, it is the same, except the screen is open at 90 degrees. This represents the zero state, and all angles are reported relative to this state.
Device orientation is reported as three angles—alpha, beta, and gamma—relative to the starting orientation along...