LIU Li1,2, TANG Gui-fen1, GUO Rui1, BAI Ying-guang1, LIU Xiao-ping1, ZHU Ling-feng1 (1. Mailbox 5136, Beijing 100094, China; 2. Key Laboratory of Dynamic Geodesy, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China) Abstract: The pseudorange is a basic observation in a satellite navigation system, and is the foundation of navigation and positioning, precise orbit determination and precise time transfer. According to the concepts and definitions of pseudorange, clock offset and timescale deviation, the influence of timescale deviation on the pseudorange measurement is discussed. By using the O-C(the difference between measured value and computed value) results of pseudorange measurements, a model for calculating timescale deviation is given. The academic analysis indicates that the influence of timescale deviation is mainly laid on the pseudorange changing rate. If the timescale deviation exists in the MEO satellite pseudorange measurements, the O-C curve will become longer, the slope of O-C curve will become larger, and the O-C curves of different observing arcs will become indention. As a result, the prediction parameters which are calculated with one observing arc will be wrong and can′t be used to other observing arcs. Finally, an experimental analysis is performed with the MEO satellite actual observing data of the compass navigation system. The results show that: 1) the accuracy of calculated timescale deviation is about 0.02 s; 2) the timescale deviations for different observing arcs are stable; 3) the O-C results with the timescale deviation removed are accordant with the theory results; 4) the correctness of the academic analysis and computational model is validated. Key words: satellite navigation system; measurement; pseudorange; clock offset; timescale deviation |
