The wide-area difference system navigation system of for the regional satellite COMPASS

The regional satellite navigation system of COMPASS （Phase I） provides both open services and authorized services. Author- ized services offer differential corrections and integrity information to users to support higher positioning, navigation and tim- ing precision. Experimenting with real data, positioning accuracy is estimated with a 3GEO/4IGSO COMPASS constellation. The results show that with dual-frequency and single-frequency pseudo-range measurements, the positioning errors are respec- tively 8 and 10 m （RMS） for open service users, while for authorized users, the errors are 4 and 5 m （RMS）, respectively. The COMPASS constellation geometry may cause large error to occur in the height component by 7-9 m for dual- or sin- gle-frequency users, which can be effectively reduced with the differential corrections supplied by the authorized services. Multipath errors are identified and corrected for COMPASS, resulting in 25% positioning accuracy improvement for du- al-frequency users and 10% improvement for single-frequency users.