ar X iv : g r - qc / 0 50 71 21 v 1 2 8 Ju l 2 00 5 Introducing Relativity in GNSS

Nowadays, the Global Navigation Satellite Systems (GNSS), working like global positioning systems, are the GPS and the GLONASS. They are based on a newtonian model and hence they are only operative when several relativistic effects are corrected. The most important relativistic effects (to order 1/c 2) are: the Einstein effect or gravitational violet shift of the frequency of the clock of the satellite (Equivalence principle of General Relativity) and the Doppler red shift of second order, due to the movement of the satellite (Special Relativity). On the other hand, in the next years the Galileo system will be constructed, copying the GPS System if there is not an alternative project. In this work, it will be also exposed that there is one alternative to the mere copy by means of the SYPOR project, using fully relativistic concepts. According to the SYPOR project, the Galileo system would be exact and without need of corrections.