Global Positioning System (GPS) has been integrated in mobile telephones for a long time; Nokia was the first to experiment with integrating GPS and mobile phones. I still have one of the first, it used and GPS cover which was sold separately. With this phone you could get the location in latitude and longitude degrees and store it for later use, pretty much as basic GPS devices, it was slow and needed open space to get a reliable position. Since, the devices have become smarter, faster, and more important global map coverage is standard. All phones have been using the US GPS system, as it is available for free, accurate and reliable. The 24 GPS satellites give 24 hours global coverage.
So what is GLONASS? GLONASS is the Russian counterpart of GPS, and the Nokia Lumia 900 supports both systems. GLONASS has an additional 21 satellites with global coverage, and by using both the amount of available satellites nearly doubles, which greatly enhances positioning capability.
Theoretically one can calculate a position using three satellites, but for better accuracy a minimum of four is needed, high buildings, forest or other objects can blocks satellite visibility, and that is why adding 21 GLONASS satellites is important.
Europe is building its own global navigation system, Galileo, but this is still under construction, and will be operational somewhere around 2020, adding 30 satellites to the present GPS and GLONASS platforms.
