Research On The Method Of GNSS Carrier-phase Time Comparison

With the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal, the application of high-precision time and frequency is playing an increasingly important role in areas of fundamental physics,and many other areas of highly advanced technology and engineering infrastructure.Meanwhile, as the wide application of high-precision time, higher performance of time comparison are demanded.GNSS carrier phase time comparison with high accuracy, simple equipment, etc,is one of the hot spots in the research of time comparison. Aims at the practical demand of GNSS carrier phase time comparison in China, this paper propose a time comparison method based on carrier phase single difference model. Firstly,according to the characteristic of carrier phase observation data, the error sources also with the correctional methods are studied in time comparison.Secondly, time comparison is realized with the method of precise point positioning and the method of carrier phase single difference. Finally, the time comparison of short, middle-long and long baseline are investigated. And the experimental results show that:(1)it is the method of precise point positioning and the method of carrier phase single difference that can achieve sub-nanosecond time comparison.(2)the time comparison precision of carrier phase single difference method is slightly higher than the precision of precise point positioning. With the advantages of real-time performance and high data utilization rate, carrier phase single difference method can reach the requirements of high precision remote time comparison in China.(3)the globally high-precision time comparison is carried out by precise point positioning method, and its accuracy is low correlation to the length of baseline.The main contents of the paper and the work are as follows:The theoretical foundation and principles of GNSS carrier phase time comparison is presented in this paper. Reference system conversion and theory foundation of parameters estimation which is used in GNSS time comparison are described in detail. Moreover, combining with the observation model of GNSS,principles of time comparison of precise point positioning method and carrier phase single difference method are demonstrated.The main error sources of GNSS measurement was analyzed. The measurement errors in GNSS is divided into four categories which relation to satellite, propagationpath, station and other factors. Additionally, a processing method is achieved with a detailed analysis of error sources and then the errors are corrected accurately by mathematical models.GNSS carrier phase time comparison is realized. The data processing methods of carrier phase time comparison in this paper mainly includes data preprocessing,the quality checking of observational data, the method of precise point positioning and the method of carrier phase single difference. The time comparison software is programmed in this paper.By analysis of the results of the time comparison of short, middle-long and long baseline, the comparison precision of precise point positioning method and the method of carrier phase single difference is assessed and the characteristics of the two algorithms in different applications are analyzed.