关键词: 卫星钟差, 模糊度固定, 星间单差, 模糊度基准, 精密单点定位

Abstract: A large number of researches suggest that integer ambiguity resolution(IAR) significantly improve the precision and reliability of precise point positioning (PPP) and providing “integer” satellite clock corrections is one of the available approaches proposed in the past ten years. In this paper, we propose a novel approach to estimate integer satellite clock corrections to support IAR for PPP application, Our approach is based on between-satellite single difference (BSSD) ambiguity fixing which contains two key steps, namely to estimate wide-lane fractional cycle bias (FCB) for satellites and to select and fix the BSSD ambiguity datum, which would recover the integer property of the wide- and narrow-lane BSSD ambiguities, respectively. This approach has been implemented in the SPODS software developed at Xi'an Research Institute of Surveying and Mapping. Experiments for clock estimation with data collected at about 66 IGS stations have been carried out to validate the proposed approach. It is demonstrated that, in the clock estimation, 73%, on average, of the independent BSSD ambiguities were successfully fixed to integers and the mean RMS and STD of differences between our clocks and the IGS final clocks are 0.170 ns and 0.012 ns respectively. The fractional parts of the wide-lane and narrow-lane BSSD ambiguities from about 448 IGS stations were analyzed, which proves that the obtained satellite clocks together with the wide-lane FCB products have the ability to support IAR in PPP. Using our products, experiments for simulated kinematic PPP with data collected at 20 IGS stations were carried out. It is shown that, with IAR, the positioning accuracy (RMS) in N, E, U and 3D are 0.009, 0.010, 0.023 and 0.027 m, corresponding to improvements of 30.8%, 61.5%, 23.3% and 37.2%, respectively, compared with that without IAR or with IGS final clocks.

Key words: satellite clocks, ambiguity fixing, between-satellite single difference, ambiguity datum, precise point positioning