OpenLayers

Class: DeviceOrientation

ol.DeviceOrientation

The ol.DeviceOrientation class provides access to information from DeviceOrientation events. See the HTML 5 DeviceOrientation Specification for more details.

Many new computers, and especially mobile phones and tablets, provide hardware support for device orientation. Web developers targeting mobile devices will be especially interested in this class.

Device orientation data are relative to a common starting point. For mobile devices, the starting point is to lay your phone face up on a table with the top of the phone pointing north. This represents the zero state. All angles are then relative to this state. For computers, it is the same except the screen is open at 90 degrees.

Device orientation is reported as three angles - alpha, beta, and gamma - relative to the starting position along the three planar axes X, Y and Z. The X axis runs from the left edge to the right edge through the middle of the device. Similarly, the Y axis runs from the bottom to the top of the device through the middle. The Z axis runs from the back to the front through the middle. In the starting position, the X axis points to the right, the Y axis points away from you and the Z axis points straight up from the device lying flat.

The three angles representing the device orientation are relative to the three axes. alpha indicates how much the device has been rotated around the Z axis, which is commonly interpreted as the compass heading (see note below). beta indicates how much the device has been rotated around the X axis, or how much it is tilted from front to back. gamma indicates how much the device has been rotated around the Y axis, or how much it is tilted from left to right.

For most browsers, the alpha value returns the compass heading so if the device points north, it will be 0. With Safari on iOS, the 0 value of alpha is calculated from when device orientation was first requested. ol.DeviceOrientation provides the heading property which normalizes this behavior across all browsers for you.

It is important to note that the HTML 5 DeviceOrientation specification indicates that alpha, beta and gamma are in degrees while the equivalent properties in ol.DeviceOrientation are in radians for consistency with all other uses of angles throughout OpenLayers.

To get notified of device orientation changes, register a listener for the generic change event on your ol.DeviceOrientation instance.

new ol.DeviceOrientation(opt_options)

src/ol/deviceorientation.js, line 65
Name Type Description
options

Options.

Name Type Description
tracking boolean | undefined

Start tracking. Default is false.
See:
Fires:

Extends

Observable Properties

Name Type Settable ol.Object.Event type Description
alpha number | undefined no change:alpha

The euler angle in radians of the device from the standard Z axis.
beta number | undefined no change:beta

The euler angle in radians of the device from the planar X axis.
gamma number | undefined no change:gamma

The euler angle in radians of the device from the planar Y axis.
heading number | undefined no change:heading

The heading of the device relative to north, in radians, normalizing for different browser behavior.
tracking boolean yes change:tracking

Changes in device orientation are being tracked.

Methods

changed() inherited

src/ol/observable.js, line 58

Increases the revision counter and dispatches a 'change' event.

dispatchEvent(event) inherited

src/ol/observable.js, line 75

Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a type property.

Name Type Description
event Object | ol.events.Event | string

Event object.

get(key){*} inherited

src/ol/object.js, line 101

Gets a value.

Name Type Description
key string

Key name.
Returns:
Value.

getAlpha(){number|undefined}

src/ol/deviceorientation.js, line 133

Rotation around the device z-axis (in radians).

Returns:
The euler angle in radians of the device from the standard Z axis.

getBeta(){number|undefined}

src/ol/deviceorientation.js, line 146

Rotation around the device x-axis (in radians).

Returns:
The euler angle in radians of the device from the planar X axis.

getGamma(){number|undefined}

src/ol/deviceorientation.js, line 159

Rotation around the device y-axis (in radians).

Returns:
The euler angle in radians of the device from the planar Y axis.

getHeading(){number|undefined}

src/ol/deviceorientation.js, line 172

The heading of the device relative to north (in radians).

Returns:
The heading of the device relative to north, in radians, normalizing for different browser behavior.

getKeys(){Array.<string>} inherited

src/ol/object.js, line 115

Get a list of object property names.

Returns:
List of property names.

getProperties(){Object.<string, *>} inherited

src/ol/object.js, line 125

Get an object of all property names and values.

Returns:
Object.

getRevision(){number} inherited

src/ol/observable.js, line 84

Get the version number for this object. Each time the object is modified, its version number will be incremented.

Returns:
Revision.

getTracking(){boolean}

src/ol/deviceorientation.js, line 184

Determine if orientation is being tracked.

Returns:
Changes in device orientation are being tracked.

on(type, listener, opt_this){ol.EventsKey|Array.<ol.EventsKey>} inherited

src/ol/observable.js, line 99

Listen for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.
this Object

The object to use as this in listener.
Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

once(type, listener, opt_this){ol.EventsKey|Array.<ol.EventsKey>} inherited

src/ol/observable.js, line 124

Listen once for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.
this Object

The object to use as this in listener.
Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

set(key, value, opt_silent) inherited

src/ol/object.js, line 150

Sets a value.

Name Type Description
key string

Key name.
value *

Value.
silent boolean

Update without triggering an event.

setProperties(values, opt_silent) inherited

src/ol/object.js, line 170

Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

Name Type Description
values Object.<string, *>

Values.
silent boolean

Update without triggering an event.

setTracking(tracking)

src/ol/deviceorientation.js, line 214

Enable or disable tracking of device orientation events.

Name Type Description
tracking boolean

The status of tracking changes to alpha, beta and gamma. If true, changes are tracked and reported immediately.

un(type, listener, opt_this) inherited

src/ol/observable.js, line 147

Unlisten for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.
this Object

The object which was used as this by the listener.

unset(key, opt_silent) inherited

src/ol/object.js, line 184

Unsets a property.

Name Type Description
key string

Key name.
silent boolean

Unset without triggering an event.