Geofencing is drawing a virtual boundary, called a geofence, around a real place and telling software what to do when a tracked item crosses it. The boundary might be a circle around a depot, a polygon around a construction site, or the doorway of a secure store. When the item enters or leaves, the system logs an event, sends an alert or starts a workflow.
Outdoors, geofences are usually built from GPS coordinates. Indoors, where GPS is unreliable, the same idea is built from readers or beacons at the boundary, which is what people mean by indoor geofencing.
How geofencing works
- Define the boundary. Draw a radius around a point or a polygon on a map, or choose the doorways and rooms that make up an indoor area.
- Assign assets. Decide which assets or categories belong inside, and who should be told when that changes.
- Detect the crossing. A GPS tracker reports a position outside the boundary, a phone scan happens outside it, or a doorway reader sees the tag leave.
- Act. Send the alert, record the event and, ideally, show who had the asset last and where it was going.
Types of geofence
| Type | Boundary made from | Works indoors? | Needs on the asset | Example |
|---|---|---|---|---|
| GPS geofence | Circle or polygon on a map | Poorly | GPS tracker or phone with GPS | Alert when a generator leaves the yard |
| Scan-location geofence | Site location plus a radius | Partly (uses the phone’s fix) | Any tag the phone can scan | Flag a tool scanned far from its home site |
| RFID reader zone | Fixed readers or portals at doorways | Yes | Passive RFID tag | Alert when a scanner leaves the IT store |
| Beacon or Wi‑Fi zone | Bluetooth beacons or Wi‑Fi access points | Yes | Powered tag or phone | Specialist indoor positioning systems |
Triggers you can set
- Exit: the asset left the area it belongs in. The most useful trigger for loss prevention.
- Entry: the asset arrived somewhere, for example a repair shop or a customer site.
- Dwell: the asset stayed inside or outside an area longer than expected.
- Out of hours: a crossing outside working hours, which may deserve a faster response.
Example: plant hire yard
Geofence: a 300 m radius around the hire yard.
A compressor with a GPS tracker leaves the boundary at 22:40 with no open hire.
An exit alert goes to the yard manager with the time and last position, while it is still close by.
Common mistakes
- Boundaries that are too tight. GPS drift of a few meters can cause false alerts at the edge; leave a margin.
- Alerts with no owner. Decide in advance who is notified and what they should do.
- Firing on legitimate moves. Exclude checked-out assets and planned transfers, or staff will soon ignore every alert.
- Using GPS for rooms. For indoor areas, use readers at the doors instead.
