[twodave]

Actually it depends on the signal, whether WiFi is turned on, etc. I used to build mobile apps for luxury clubs who wanted to know which members were arriving at the club (e.g. to go ahead and start getting their golf clubs ready. First world problems, I know). The GPS data we get access to for both Google and Apple includes lat/lng plus a radius in meters that represents the accuracy of the measurement. Depending on the different factors it can be over 100m or as little as about 5m.

[nitrogen]

Did the club members have to install an app, or were you able to get the data some other way?

[twodave]

They had to install the app and also consent to have their location tracked by the club. They could still use the app without that stuff, obviously, and the platform actually didn’t allow club admins to see where members were at all times—just which members were entering/exiting designated areas. It was actually quite a challenge to get that kind of information to the club in a timely fashion, especially if the club was situated near a busy roadway. You wanted the geofence large enough to give the club time to prepare to receive the guest, but not so large that it gave false positives for members simply driving past the club.

[laurent92]

Could you have pinged a server that only existed on the public wifi, and made the public wifi keyless?

[twodave]

An actual connection is not necessary for wifi to contribute to location accuracy. It just uses signal strength to available access points to triangulate. How folks like Google/Apple/etc. are able to get accurate location data for those access points is unknown to me.

[judge2020]

https://www.zdnet.com/article/how-google-and-everyone-else-g...

https://support.apple.com/en-us/HT207056#:~:text=If%20Locati....

TLDR Android & iOS Location Services will automatically contribute wifi data and correlate it with GPS. This can be audited to prove it's anonymously uploaded but it does happen.