Research On One-station And Multi-station Combined Monitoring Method Of GNSS System Time Offset

Multi-mode satellite navigation is an important development direction of Global NavigationSatellite Systems (GNSS), and one of the key issues that should be solved to implementmulti-mode satellite navigation is to realize compatibility and interoperability among GNSSsystem time.According to the requirements for the development of multi-mode satellite navigation, amethod of monitoring GNSS system time offset is researched by means of reception ofSignal-in-Space (SIS). At beginning of this case, the monitoring principle and the errordistribution of one-station monitoring GNSS system time offset is described. The monitoringaccuracy of one-station is improved with IGS precise ephemeris. Then, based on anaylsis offeatures on one-station monitoring methods, a method of multi-station combined monitoringGNSS system time offset is proposed. Meanwhile, a system based on the method is designed andconstructed. After three months test, plenty of data are analyzed and the results show that thesystem runs stably and reliably, the monitoring method by multi-station is reasonable and thedesign of multi-station monitoring system of GNSS system time offset is reasonable.The main works of this paper are shown as follows:The generations of GNSS time system and system time offset between GNSS are analyzed;Several monitoring methods of GNSS system time offset are discussed, and thecharacteristics of each method are analyzed. In this paper, one-station monitoring GNSS systemtime offset by reception of SIS is mainly researched and its errors distribution is analyzed. Inorder to correct some errors of the mornitoring method, a method of receiver delay calibrationbased on UTC (NTSC) is applied and its results are gained. Meanwhile, the influences ofsatellite elevation on ionosphere correction and troposphere correction as well as monitoringresults are analyzed. In addition, a correction method of system time offset measuring results isstudied with IGS precise ephemeris. Furthermore, circular T bulletin data published by BIPM isapplied to evaluate the results of both monitoring and correcting, which shows that the accuracyof one-station monitoring GNSS system time offset is improved by means of correctingbroadcast ephemeris error with IGS precise ephemeris.Based on one-station monitoring method of GNSS system time offset, a method ofmulti-station combined monitoring is proposed. The necessity of this method is expounded, andthe design principle of which is researched, as well as error source of the method is analyzed. Inaddition, the algorithm of this method is mainly studied. In view of above studies, a systembased on this method is designed and construced. This system consists of hardware and software. As for the system before operation, it should be calibrated by zero-baseline comparisonexperiment. At last, the debugging results of this system compared with circular T bulletin datashow that multi-station combined monitoring method of GNSS system time offset is reasonable.Through the analysis of one-station and multi-station combined monitoring results of GNSSsystem time offset, monitoring accuracy of5ns is realized by two monitoring methods. And themonitoring accuracy is equivalent to the GGTO (GPS to Galileo Time Offset) index designed byGalileo.