Yes, and as tcope may be referring to, the software compensates for all kinds of things including the Einstein's general theory of relativity. My colleagues at the office were having a discussion about this a couple of weeks ago, in the context of accurate timekeeping and how the nuts and bolts of our broadcast studios all stay in sync. The following pages were brought up as being excellent resources:Don't GPS receivers on Earth use some kind of time-shift measurement calculation to determine your position?
Gravity's Effect on Spacetime — NOVA | PBS
GPS and Relativity