Physics Forums - The Fusion of Science and Community

I understand that all GPS satellites have the same orbital inclination, so wrt a fixed position on earth, the average velocity over time of the GPS satellites is the same for all of the satellites. So I can safely ignore the effect of the orbit on the amount of time dilation. But what about the position on Earth? For example, the velocity of an observer at the north pole is very different from the velocity of an observer...