Yes, compared to lat and long. A good 2D GPS fix is easiest when you have a few satellites in different compass directions, say one at each of N,S,E,W. But for

Yes, compared to lat and long. A good 2D GPS fix is easiest when you have a few satellites in different compass directions, say one at each of N,S,E,W. But for 3D, it is impossible to see a satellite underneath you. You have a bunch of them above you, and you need to difference the times of their signals' arrival. For more, see here: http://gpsinformation.net/main/altitude.htm http://gpsinformation.net/main/altitude.htm