GNSS interoperability: offset between reference time scales and timing biases

Within the GIOVE Mission (GIOVE-M), two experimental satellites called GIOVE-A and GIOVE-B have been launched by the European Space Agency. This paper analyses the different issues involved in GPS/GIOVE interoperability for positioning and timing, including GGTO (the GPS to Galileo time offset) and timing biases, and presents practical experience and results related to EGGTO, the GIOVE-M experimental version of GGTO broadcast within the GIOVE navigation messages.