# Geofences

A geofence is a boundary that you can define and associate with your devices. The area that the geofence encloses can be defined using geographic coordinates or radio measurements.

Geographic geofences can be circular or polygonal. Circular geofences are defined by geographic coordinates of its center and a radius while polygonal geofences are defined as a set of geographic coordinates. Indoor geofences can be created by adding the floor properties to the geofence definition.

POI geofence (Point Of Interest) is a geofence whose boundary is defined using radio measurements. POI geofences need to be trained separately using a telemetry that a device has recorded while being in the desired point of interest. The device is considered to be inside the POI geofence when the radio measurements of the device-ingested telemetry and the training data match.

Once created, a geofence can be associated with a device. This association means that every time a position or a radio measurement update is received from the device, it will be checked if the device has transitioned across the boundary of the geofence. If the device has transitioned from outside to inside of the geofence or vice versa, a transition event is recorded and HERE Tracking will generate a notification. For indoor geofences a transition is recorded only if the position of the device is indoors, and the floor details of the position match the geofence floor definition.