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.
Today, the newly announced Samsung Galaxy Alpha as well as the newly launched Xiaomi Mi4 have GPS, Glonass and Beidou.
- 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.