A geo-fence is made of virtual boundaries that do not need to be carried or mended. While geo-fences do not limit movement in the same way as fences or walls, they can stand watch over an area and monitor what goes on inside of it.
Though there are many ways of generating a geo-fence, the most useful type for commercial and institutional projects is established by drawing boundary lines outlining the mapped property one wants to monitor.
Geo-fences provide much of the same access monitoring functionality as physical perimeter monitors, but without the limitations of fields of view or physical maintenance often required by those sensors. Geo-fences can be also used to trigger alerts or operate linked devices to limit actions that can be taken within the fenced area.
In his latest blog on the CSI website, Gregory Ceton, CSI, CDT, provides a brief introduction to geo-fences.