Time Scales and Time Transformations Among Satellite Navigation Systems

The definitions of time scales and the time transformations are very important for Global Navigation Satellite Systems (GNSSs) research. Different GNSSs use different internal reference time systems which include GPS Time, GLONASS Time, GALILEO System Time and BeiDou System Time. With the development of GNSSs, it is significant to set up the relationships of time scales among different GNSSs to improve the compatibility and interoperability. This paper concludes the definitions of different time scales and describes the time systems in different GNSSs firstly. Secondly, the relationships among different time scales are analyzed according to the data published by Bureau International des Poids et Mesures (BIPM) in recent years, and time transformations among different time systems are presented. Finally, these transformations are tested and validated, and the result shows that they can satisfy the accuracy requirements for most users.