LIU Li1,2，HAN Chun-hao1,2，ZHU Ling-feng2，GUO Rui2，LIU Xiao-ping2

(1. Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai 200030, China;

2. P. O. Box 5136, Beijing 100094, China)

Abstract: According to the definitions of pseudorange and clock offset, the fundamental of time transfer of electromagnetic signal is discussed. The calculation models based on pseudorange in the geocentric non-rotating coordinate system are derived in detail. By means of coordinate transforming, the practical models in the Earth-fixed coordinate system are given. As a result, the correction from satellite movement in the Earth-fixed coordinate system is different from the correction of Sagnac effect. For GEO satellite, the maximum of Sagnac correction is 200 ns and the correction from satellite movement is about 1 ns. For MEO satellite, the maximum of Sagnac correction is 120 ns and the correction from satellite movement is about 1 200 ns.

Key words: satellite navigation system; coordinate system; pseudorange; time transfer; clock offset