卫星钟差解算及其星间单差模糊度固定

Satellite Clock Estimation with Between-satellite Single Difference Phase Ambiguity Fixing

整数相位模糊度解算可以显著提高GNSS精密单点定位(PPP)的精度。本文提出一种解算卫星钟差的方法,通过固定星间单差模糊度恢复出能够支持单台接收机进行整数模糊度解算的卫星钟差,即所谓的"整数"钟差。为了实现星间单差模糊度固定,分别通过卫星端宽巷FCB解算和模糊度基准的选择与固定恢复出宽巷和窄巷模糊度的整数性质。为了证明本文方法的可行性,采用IGS测站的GPS数据进行卫星钟差解算试验。结果表明,在解算钟差时,星间单差模糊度固定的平均成功率为73%。得到的卫星钟差与IGS最终钟差产品相比,平均的RMS和STD分别为0.170和0.012ns。448个IGS测站的星间单差宽巷和窄巷模糊度小数部分的分布表明本文得到的卫星钟差和FCB产品具备支持PPP用户进行模糊度固定的能力。基于以上产品开展了模拟动态PPP定位试验,结果表明模糊度固定之后,N、E、U和3D的定位精度(RMS)分别达到0.009、0.010、0.023和0.027m,与不固定模糊度或采用IGS钟差的结果相比,分别提高了30.8%、61.5%、23.3%和37.2%。

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.