综合伪距相位观测的北斗导航系统广域差分模型

摘要

BeiDou Navigation Satellite System (BDS)integrates legacy PNT service and authorized SBAS service,where SBAS service provides differential corrections and integrity information for authorized users. Current BDS differential corrections include one-dimensional equivalent satellite clock and ionospheric grids corrections,which is derived based on CNMC-smoothed pseudo-range observations.To improve the performance of BDS SBAS service,an algorithm is developed to estimate the real-time satellite clock and orbit corrections.In the algorithm,phase smoothed pseudo-range observation is used to define absolute value,and epoch differenced phase observation is used to define epoch-wise variation of the satellite clock/orbit corrections.It is analyzed that the impact of data sampling rate and station number on the correction parameter estimation.Real-time data of the BDS tracking network in China is used to validate the new algorithm.Compared with the current system performance:① mean UDRE using the new algorithm is reduced by 27%,35% and 27% for GEO,IGSO and MEO satellites,② mean positioning error using the new algorithm is reduced by 23%,32% and 52% in the North,East and Up components,respectively. Implementing the new algorithm,BDS SBAS service supports the user positioning requirement with accuracy better than 1 m.%我国区域北斗卫星导航系统为用户提供开放服务和授权服务两种服务方式,其中授权服务主要提供一维等效钟差改正数和完好性信息,实现更高精度的服务性能.北斗卫星导航系统提供的实时差分信息是基于C NMC平滑后的伪距观测数据计算,其精度受到残余伪距噪声的限制.为提升系统广域差分服务性能,本文提出了一种广域差分新模型.该模型综合了伪距及相位观测数据,并新增了轨道改正数.模型中经相位平滑的伪距观测值用于定义钟差改正数和轨道改正数的基准,而相位历元间差分观测值用于计算约束差分改正数的高精度相对变化.论文分析了数据采样率、测站个数等因素对新模型的影响,并采用中国区域内的观测站数据对新模型进行精度验证.试验结果表明:①基于新广域差分模型的GEO卫星UDRE指标相对原有模型提升了27%,IGSO卫星指标提升了35%,MEO卫星指标提升了24%;②基于新的广域差分模型,用户在南北、东西、高程方向的伪距定位精度分别提升了23%、32%和52%,实现了北斗系统用户导航定位三维定位精度优于1 m的指标.