Your smartphone likely works with both the Global Positioning System (GPS) and Assisted GPS (A-GPS). GPS gets its information from the constellation of satellites that orbit the Earth. Assisted GPS, also called A-GPS or AGPS, gets its information from local cell towers and improves on the performance of standard GPS on mobile devices connected to a cellular network.
How GPS Really Works on Your Phone (Not What You Think)
Assisted GPS improves location determination in two ways:
A GPS system must establish satellite contacts and find orbital and clock data before it can determine its location. This is the period known as the Time to First Fix (TTFF).
The process can take anywhere from 30 seconds to a few minutes for your device to pick up a signal; how long exactly depends on the environment and the amount of interference. It’s easier to pick up a signal in wide-open spaces than in a city with tall buildings.
