Science and Tech


Geofence: The Invisible Way Companies Use Data To Track You Everywhere

If you've ever used location-based filters or stickers on social media, you've probably passed through a geofence.
Posted at 8:47 PM, Apr 16, 2019

You're all fenced in and probably don't even know it.  The boundary is invisible but very real. 

It's a geofence.

We walk in and out of them all day long. 

geofence is a virtual perimeter drawn around a geographical area. It can outline a restaurant, an airport, a shopping mall, doctor's office. And the shape can be a circle, maybe 100 feet around a store, or some other shape.

Typically, a programmer builds the fenced area using GPS- or RFID-enabled software which is used to locate us, usually with a phone. 

Here's what happens, using a grocery store as an example: The store hires a programmer to set up a geofence around the store. A programmer can also design a mobile app. Being a loyal customer, you download the app, which enables location services. Walking into or near the store triggers the geofence, sending alerts for specials — maybe a new chardonnay or double-chocolate ice cream. The store makes more money, and you get tailored coupons. Apps aren't necessary; hooking up to a Wi-Fi connection can do the same. But it doesn't stop there. Marketers team up with data brokers and follow you everywhere — from work to church to the voting booth or couch. explains a typical workflow: 

"The data used to serve the ads was gleaned from user behavior on apps and via IP addresses, information that is regularly harvested by data brokers who repackage it to marketing firms who use it to serve ads with laser-like precision based on interest, location, age and many other markers." 

While each person is technically anonymous, their identifying factors are all being compiled, including browsing history.  And it's legal. 

A few more geofencing scenarios: 

    • At work: Time cards can be automatically triggered when an employee crosses into a company's geofence and when the employee leaves. 

    • Drones: A no-fly zone can be set up around a sporting event or an airport. 

    • Special events: People attending an outdoor concert can get messages on their phones about the venue and other announcements.

There are some innocuous, even helpful, uses.  

But all of the possible applications — by people you may not realize are watching —  add up to this: A geofence is invisible, but in the virtual world, you're not.