Ground-based radio beacons emit a signal which is picked up by receiving satellites.

This is in reverse configuration to other GNSS, in which the transmitters are space-borne and receivers are in majority near the surface of the Earth.

A frequency shift of the signal occurs that is caused by the movement of the satellite (Doppler effect).

For the installation of a beacon only electricity is required because the station only emits a signal but does not receive any information.

The accuracy is a bit lower than with GPS, but it still contributes to the International Terrestrial Reference Frame (ITRF).