When tracking the GPS position of a person or other entity, Geofencing is an important component of that tracking process. A geo-fence is a virtual boundary around an area, and transgressions into or out of that area can be used to trigger events within a platform.
Typically geofences are one of:

  • Intrusion - the entity has entered a geofenced area
  • Absconsion - the entity has exited a geofenced area

A time element may also be considered, whereby the geofence may only be active at certain times of day, or just active for a single period.

Geofencing has a number of applications including sports tracking, warehousing, proximity-targeted marketing and personal monitoring.

Geofences can be any shape, but are typically square, circular or a polygon representing the boundary of a restricted area (such as a building or industrial complex. Of course, it is rare that real-world areas are exact geometric shapes, but often simple geometric shapes are good enough for the application and the maths of calculating whether an entity is in or out are much more simple. More recently, database platforms support such calculations of boundaries and intersections, such as the Geospatial and Geometry support in SQL Server.


This simple demo shows the trace of a person moving about Bracknell town centre, and highlights when their location is inside of a number of circular geofenced areas.

Use the Play & Pause buttons to show the last hour of the person's movements or the slider to position the track at any point.


Speed (kph): 


Time entered:
Time exited: