Geofence is a portmanteau of the words geographic and fence. Geofence areas can be circles, rectangles but also more complex areas by fixing their coordinates or a radius in the navigation satellite system.
How does geofencing work?
Geofencing means the automated triggering of a function when entering or exiting a defined geographical geofence area. For this purpose, the observed object sends its position via GPS at regular intervals. It permanently receives the current time and position data from at least three, ideally four satellites, allowing conclusions to be drawn about its position. If the user of a GPS-enabled device, such as a smartphone, enters the digitally ‘fenced-in’ area, this triggers an action or interaction. This content is first stored in a cloud.
Advantages of geofencing
GPS is integrated into every smartphone; the range is high, and the functions are well known, trusted and accepted among smartphone users.
Tips for implementing geofences can be found here: https://www.wingu.de/wie-funktioniert-geofencing.