Geolocation

The Geolocation object allows the user's current geographical location to be estimated. Note not all devices support geolocation (use the Is supported condition to check), and of the devices that do, the accuracy can vary significantly. For example a desktop computer might not come with any location-tracking equipment, and only be able to report a location accurate to a 50 kilometer radius based on their internet connection. However this at least allows for the user's timezone, country, or possibly city or town to be determined. On the other hand many mobile phones and tablets come equipped with GPS equipment and can report their location as accurately as within a few meters, and track movements in real-time.

For an example of the Geolocation object, see the Geolocation example in the Start dialog.

Permission prompts

When requesting the user's location, for privacy reasons most platforms will prompt the user for permission. Each platform tends to have its own specific way of asking for permission. The user may decline the permission request, in which case On error will trigger. Your projects should handle such a case gracefully if possible. Normally each browser or platform has a way to grant permission when it was previously declined, but it either involves prompting again, or making changes in the browser or app platform settings. Some platforms will fail without even prompting the user after a single declined permission request.

Battery usage

It should be noted that tracking the user's location may involve activating GPS hardware in a phone or tablet, which can drain the battery more quickly. Requesting high-accuracy location information is also likely to use more power. Try to only request the user's location if absolutely necessary, use low accuracy if suitable, and request one-off positions rather than watching the position for a long time.

Geolocation conditions

Is supported
True if the current device supports reporting the user position with geolocation. If false, none of the features of the object will work.

Is watching location
True after a successful Watch location action, until the Stop watching action is used.

On error
Triggered if an error occurs when requesting permission for, or retrieving, the user's location. The ErrorMessage expression contains more information about the problem in this trigger.

On location update
Triggered after a successful Request location or Watch location action, when the position has been updated. This only triggers once after a successful Request location action, but can trigger regularly after a successful Watch location action whilst the position is tracked and updated.

Geolocation actions

Request location
Make a one-off request for the user's current location. The user may see a permission prompt which they must approve before any information is returned; if they decline, On error will trigger. Accuracy can be set to High to get more accurate results, but it may take longer to calculate and consume more battery. Timeout is the maximum time in seconds the device may take before it must return a position or trigger On error. Maximum age is the maximum age of a cached result that can be returned. If zero, the device will actively try to determine the user's position at that time. However if it is nonzero, and the operating system had previously requested the user's position within that time, the previous result may be returned immediately instead. This is faster and can save battery, but the result will not be as close to real-time. If a result is successfully determined, On location update will trigger.

Watch location
As with Request location, but the location will be tracked. On location update will trigger whenever new position information is available, until the Stop watching action is used. Watching the location can consume more battery on mobile devices than one-off requests.

Stop watching
Stop a previous successful request to watch the user's location. The position will no longer be updated.

Geolocation expressions

The position-related expressions only update when On location update triggers, which in turn can only occur after a successful Request location or Watch location action.

Accuracy
AltitudeAccuracy
The estimated accuracy in meters of the latitude and longitude (for Accuracy) or the altitude (for AltitudeAccuracy). The accuracy may be more or less a guess, or if it is not known the expression returns 0.

Altitude
The estimated altitude in meters relative to sea-level, or 0 if not known.

ErrorMessage
In On error, a string with some additional information about the error.

Heading
Speed
While watching a position, the direction of travel in degrees relative to due north and speed in meters per second if available, else 0 of not available.

Latitude
Longitude
The latitude and longitude that has been determined, subject to the Accuracy (which may not be known).

Timestamp
A timestamp of the time at which the current details were retrieved. This is measured in milliseconds since midnight, January 1, 1970.

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