> The best GPS resolution available to civilians is about 8 meters (26 feet) - and that's under the best, most ideal situation using the best GPS receiver and a large antenna... things a small cell phone in a pocket or bag doesn't have.

I am not sure where you got this from but that is incorrect - the accuracy (or resolution) depends entirely on the number of satellites and/or augmentation systems you're tapped into, and how strong / clear those signals are. It can vary from a few kilometres down to a few centimetres.

Back in the 90's "Selective Availability" was a thing but it has since been removed.

See https://www.gps.gov/systems/gps/performance/accuracy/

Also - most modern phones can and do tap into the major providers (Galileo, Glonass, GPS etc), towers, WiFi spots, beacons and use all of these to give a a VERY accurate position of where the device is.

Edit: Might mention I worked first hand on indoor tracking of users, and a warehouse project for optimising worker picking - we were able to easily distinguish where a person was in a busy retail setting down to which section of a clothes rack they were selecting clothes from, and exactly where a worker was in a very interference-heavy (metals) warehouse floor using the above mentioned technologies.