Assessment method and analysis of broadcast coordinated universal time offset error

Coordinated universal time offset error(UTCOE) which is the error of broadcasted coordinated universal time offset(UTCO) has become one of the focuses that global navigation satellite system(GNSS) provider and its users are concerned in recent years. This paper studies UTCOE definition, proposes an indirect assessment method of UTCOE based on Coordinated Universal Time(UTC) kept by National Time Service Center( UTC(NTSC)) and circular T bulletin published by International Bureau of Measurement(BIPM).The validity of the method is verified by using direct assessment method of GPS UTCOE. Furthermore, uncertainty budget of the assessment method is also given. The UTCOE of BDS, GPS and GLONASS are assessed utilizing the monitoring data from the running GNSS system time offset monitoring system at NTSC. During the assessment cycle throughout 2018, the root mean square (RMS) of BDS UTCOE is 17.33 ns. The 95% statistical value of UTCOE of BDS, GPS and GLONASS are 35.47、2.08 and 8.64 ns, respectively. The results show that the UTCOE of BDS, GPS and GLONASS all meet their own standard performance specifications. The UTCOE assessment results of GPS are far superior to its performance commitment. GLONASS is the second. BDS UTCOE assessment results are critical and show obvious systematic error characteristic. So, the UTCOE of BDS has a large room for promotion.