Modern cell phones use A-GPS (Assisted GPS): https://en.wikipedia.org/wiki/Assisted_GNSS https://en.wikipedia.org/wiki/Assisted_GNSS I also remember back in the

Modern cell phones use A-GPS (Assisted GPS): https://en.wikipedia.org/wiki/Assisted_GNSS https://en.wikipedia.org/wiki/Assisted_GNSS I also remember back in the early 2000s we were using a GPS-quipped PDA as a turn-by-turn navigation device, and for the first ten minutes the device simply asked us to wait. At that time the signal was intentionally degraded in a process called Selective Availability (https://www.gps.gov/systems/gps/modernization/sa/ https://www.gps.gov/systems/gps/modernization/sa/). I didn't have any experience with that.