Triggers

A trigger is a mechanism that detects an occurrence, and can cause additional processing in response. Triggers are activated when a change occurs in the device context.

Triggers can be activated for changes in Geo or WiFi data.

Geo triggers

For Geo data, two types of regions, also known as geofences, are considered: circles and polygons. The following trigger types are available for Geo data.

Trigger type	Description
PositionChange	The trigger is activated when the position of the device changes by at least a specified distance.
Enter	The trigger is activated when the device enters a region.
Exit	The trigger is activated when the device leaves a region.
DwellInside	The trigger is activated when the device remains inside a region for a given time period.
DwellOutside	The trigger is activated when the device remains outside a region for a given time period.

For Enter, Exit, DwellInside, and DwellOutside, we can increase or decrease the size of the region by altering the buffer zone width. Sensor accuracy is measured using GPS coordinates and network accuracy.

We can control trigger activation based on confidence levels. For example, if you choose a confidence level of low, accuracy is not taken into account when you are determining whether a geo-locational coordinate acquired from a device is inside or outside a region. If we choose a confidence level of medium, accuracy is taken into account, and we can be sure that the coordinate lies within, or outside of, the region at approximately a 70% confidence level. If we choose a confidence level of high, accuracy is taken into account, and we can be sure that the coordinate lies within, or outside of, the region at approximately a 95% confidence level.

WiFi triggers

For WiFi data, triggers are activated based on a change in visible access points. Access points are defined using SSIDs (service set identifiers) and MACs (media access control addresses). The following trigger types are available for WiFi data.

Trigger type	Description
VisibleAccessPointsChange	The trigger is activated when the visible access points that define a WiFi area change by a specified amount.
Enter	The trigger is activated when the device enters a WiFi area.
Exit	The trigger is activated when the device leaves a WiFi area.
DwellInside	The trigger is activated when the device remains inside a WiFi area for a given time period.
DwellOutside	The trigger is activated when the device remains outside a WiFi area for a given time period.
Connect	The trigger is activated when the device connects to a WiFi access point.
Disconnect	The trigger is activated when the device gets disconnected from a WiFi access point.

We can control trigger activation based on confidence levels. A low confidence level is used to indicate that the WiFi acquisition policy signalStrengthThreshold value is used when determining whether an access point is visible. A medium confidence level is used to indicate that a signal strength of at least 50% is necessary for an access point to be visible. A high confidence level is used to indicate that a signal strength of at least 80% is necessary for an access point to be visible.

When we use the confidence level to determine whether an access point is visible, each specified access point in the area must be at least as strong as that indicated by the confidence level. If the area access point is for an SSID without a MAC address, then the highest signal strength for that SSID must be at least as strong as that indicated by the confidence level. To exit the area, the signal strength level for at least one access point must be below the WiFi acquisition policy signalStrengthThreshold value.

For WiFi triggers, the confidenceLevel parameter is not supported by DwellOutside.

For detailed information about the parameters for the trigger types, see the startAcquisition method as defined in the WL.Device class.

Parent topic: Location services