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Geo-Fences: Lines and Spaces

By Gregory Ceton, CSI, CDT posted 09-05-2019 11:39

Oh, just another kind of out-door game,
One on a side. It comes to little more:
There where it is we do not need the wall:
He is all pine and I am apple orchard.
My apple trees will never get across
And eat the cones under his pines, I tell him.
He only says, ‘Good fences make good neighbors.’
—Robert Frost, Mending Wall

Unlike the rough-hewn stone wall in Robert Frost’s poem, a geo-fence is made of virtual boundaries that do not need to be carried or mended. Geo-fences do not limit movement like fences or walls, but they can stand watch over an area and monitor what goes on inside of it. Though the boundary-setting function is central to geo-fencing, a better term for the what a geo-fence provides may have been “geo-watchdog.”

Geo-fences are built on the same kind of geospatial information and standards that underlie your car navigation system. Though there are many ways of generating a geo-fence, the type most usable by commercial and institutional projects is established by drawing boundary lines outlining the mapped property one wants to monitor. Google Earth is often reference for the location data in geo-fence code, though other organizations offering geo-location services, such as Esri, can also provide the data needed to establish a geo-fence. Use of geospatial information is becoming more common—recently the CSI Puget Sound Chapter sponsored a geocaching treasure hunt that leverages the same technology.

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 used to trigger alerts or operate linked devices to limit actions that can be taken within the geo-fenced area.

A geo-fence can be active or passive. An active geo-fence requires someone within the geo-fence to opt into location tracking. This type of geo-fence can be used to track and communicate with students and faculty in a campus security application. A passive geo-fence tracks without the person opting in. In the campus example, a passive geo-fence could be layered onto the active one and used to track non-students and non-faculty in the same emergency. The tracking of activity or location is performed using cell traffic or a radio-frequency identification (RFID) tag, such as those inserted in ID badges or entry tokens.

As mentioned in a past article on “Creating Smart Cities", temporary geo-fences can be used to manage and help ensure the safety of first responders in a potentially hazardous emergency site by monitoring their vitals, location, and movement. Also mentioned in that article was the idea of autonomous vehicles driving down valleys of data formed by smart building servers. These functions and others are central to the idea of a smart city and its management. Geo-fencing and location-based services will be used extensively in mature smart cities for many functions, all of which will provide the data needed for the city to operate efficiently.

Among the most promising current uses of geo-fencing are for healthcare and school and public facility security. A passive geo-fence around a healthcare facility can provide an additional layer of patient monitoring with fewer hardwired sensors. It can be linked to health tracking wearables that double as patient ID bracelets to identify hard fall situations and monitor vital signs in a typical hospital setting or to help prevent wandering offsite in a lower cost and less intrusive or restrictive way than currently required for patients, especially those with mental illness or dementia, in long-term care facilities.

A geo-fence can also help provide security for a school or public facility by tracking employee and student locations through ID badges or triggering devices to prevent or limit use of unauthorized cell phones. Additionally, a geo-fence can inform authorities when a person has passed a geo-fenced boundary if it occurs at an unusual time or the intruder remains for more than a pre-established duration. This allows monitoring officials to see real areas of possible concern and distinguish an unauthorized entry from a simple student drop-off or pick-up. Using passive monitors to track and identify people is very helpful in emergency situations when ready information can save lives.

As more devices gain location-aware capabilities, more of their functions can be monitored and controlled within geo-fences. Location-awareness chiefly applies to car device and cell traffic now, but as noted in the recent article about “Artificial Intelligence and the Internet of Things (IoT)”, more devices are being enabled with cell-based reporting functions and location awareness every day. These new functions will quickly become a desirable selling point, making geo-fences ever more present and useful.