My first smartphone was an Acer Liquid. Among the many marvels of a touchscreen smartphone based on Android, it had GPS as a support for the then-infant Google Maps.
Later on I moved to a Galaxy Note 2 (not my second, mind you). This one had better positioning using both GPS and Glonass.
- GPS is the "classic" western navigation system. Currently using 31 satellites (as of 2014), it provides accurate position of up to 8 meters with a 95% confidence limit (civilian accuracy) provided there is unobstructed view on at least 4 satellites from the network.
- A-GPS means "assisted GPS", where GPS positioning is enhanced with information transmitted over Wi-Fi and/or cellular networks.
- GLONASS: it's the Russian equivalent of GPS, currently offering 24 satellites with global coverage (should have been 30, but 6 were lost at launch time in two separate incidents) as of 2014. Civilian accuracy of the GLONASS system is around 10 meters.
- Beidou: the Chinese equivalent of GPS. Beidou currently offers 15 satellites with stable coverage of the Northern Hemisphere. The commercial accuracy is 10 meters.