Amongst other things, the clocks need to be corrected for relativistic effects. Due to the net effect of both kinetic and gravitational time dilation, clocks o

Amongst other things, the clocks need to be corrected for relativistic effects. Due to the net effect of both kinetic and gravitational time dilation, clocks onboard a satellite advance more quickly than they would on Earth (when observed from Earth). https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Globa...