Counterexample and example of the principle of relativity.

In the Earth-centered locally inertial coordinate system, the Principle of Relativity is not satisfied when using the experimental data of the global positioning system (GPS). The clocks in the GPS satellites tick off time more slowly by the velocity vG=4 km/s after elimination of the gravitational effects. Between two local gravity fields, the Principle of Relativity is satisfied. [ABSTRACT FROM AUTHOR]