An Explanation of Wi-Fi Triangulation

Learn how Wi-Fi GPS works to track your location

Hand holding smart phone on world map network and wireless communication network, abstract image visual, internet of things.Elements of this image furnished by NASA
Prasit photo / Getty Images

Wi-Fi Positioning System (WPS) is a term pioneered by Skyhook Wireless to describe its Wi-Fi-based location system. However, other companies like Google, Apple, and Microsoft use GPS to determine Wi-Fi networks too, which can then be used to find someone's location based solely on Wi-Fi.

You might sometimes see a GPS app ask you to switch on Wi-Fi to get a more accurate location. It probably seems weird to assume that your Wi-Fi as anything to do with GPS tracking, but the two can actually work together for a more precise location.

Wi-Fi GPS, if you want to call it that, is particularly useful in urban areas where there are Wi-Fi networks broadcasting all over the place. However, the benefits are even greater when you consider that there are some circumstances where it's simply too difficult for GPS to work, like underground, in buildings or malls where GPS is too weak or intermittent.

Something to remember is that WPS does not work when out of range of Wi-Fi signals, so if there aren't any Wi-Fi networks around, this WPS feature will not work.

Note: WPS also stands for Wi-Fi Protected Setup but it's not the same as Wi-Fi Positioning System. This can be confusing since they both pertain to Wi-Fi but the former is a wireless networking system that's intended to make it faster for devices to connect to a network.

How Wi-Fi Location Services Work

Devices that have both GPS and Wi-Fi can be used to send information about a network back to a GPS company so that they can determine where the network is.

The way this works is by having the device send the access point's BSSID (MAC address) along with the location determined by GPS.

When GPS is used to determine the location of a device, it also scans nearby networks for publicly accessible information that can be used to identify the network. Once the location and nearby networks are found, the information is recorded online.

The next time someone is near one of those networks but they don't have great GPS signal, the service can be used to determine an approximate location since the network's location is known.

Let's use an example to make this easier to understand.

You have full GPS access and your Wi-Fi is turned on in a grocery store. The location of the store is easily spotted because your GPS is working, so your location and some information about any nearby Wi-Fi networks are sent to the vendor (like Google or Apple).

Later, someone else enters the grocery store with Wi-Fi on but no GPS signal since there's a storm outside, or maybe the phone's GPS just doesn't work well. Either way, the GPS signal is too weak to determine the location. However, since the location of nearby networks is known (since your phone sent that information in), the location can still be gathered even though GPS isn't working.

This information is constantly being refreshed by vendors like Microsoft, Apple, and Google, and all of it used to provide more accurate location services to their users. Something to remember is that the information they gather is public knowledge; they don't need any Wi-Fi passwords to make it work.

Anonymously determining user locations in this way is part of virtually every cell phone carrier's terms-of-service agreement, though most phones allow the user to turn off location services.

Similarly, if you don't want your own wireless network to be used in this way, you might be able to opt out.

Opt out of Wi-Fi Tracking

Google includes a way for Wi-Fi access point administrators (that includes you if you have home Wi-Fi or control your office Wi-Fi) to opt out of its WPS database. Simply add _nomap to the end of the network name (e.g. mynetwork_nomap) and Google will no longer map it.

See Skyhook's Opt-Out page if you want Skyhook to stop using your access point for positioning.