【作者】 徐磊；

【导师】 李亮； 常国宾；

【作者基本信息】 中国矿业大学 ， 大地测量学与测量工程， 2019， 硕士

【摘要】 电离层时延作为无线电导航定位主要的误差源之一,是GNSS导航误差改正必须考虑的误差。对电离层建模和预测不仅可以改正广大单频用户的电离层时延,还能加快双频/多频用户的定位收敛速度。频间偏差作为电离层格网的附属产品,不仅对电离层建模精度有所影响,还对修正不同观测量组合定位间的钟差基准有重要意义。国际上各卫星导航服务与分析中心一直致力于提高电离层产品精度与时效性,以满足用户工程测量与科研工作的要求。自2018年起,中国矿业大学北斗数据分析中心开始进行全球实时电离层产品解算,目前还处于内测阶段,并未对外发布电离层产品。针对上述问题,本文解算了北斗卫星频间偏差,分析了北斗数据中心电离层产品精度,主要内容如下:(1)阐述了GNSS导航定位的基础理论与电离层监测与建模的理论方法。包括:观测量常用线性组合方案,对比了各方案的适用条件和优缺点;总结了数据处理流程中两种周跳探测方法的优缺点并作了实验说明;介绍了常用的电离层监测与建模方法与理论。(2)提出了一种基于闭合差约束的北斗二代卫星多频频间偏差估计方法。通过实验对比,估计的多频频间偏差与CAS估计的频间偏差精度相当;由于测站条件的限制,本文估计的频间偏差和CAS估计的频间偏差稳定性略低于DLR发布的产品。分析了频间偏差改正对不同定位模式不同观测量组合定位结果的影响。(3)阐述了中国矿业大学北斗数据处理中心的全球实时电离层产品生成原理与方法,并把实时电离层产品与iGMAS武汉大学分析中心的事后电离层产品whug进行精度对比,统计信息表明实时电离层产品与事后的产品精度相当,较差在5TECu以内,符合电离层产品的精度要求。另外,还分析了实时电离层产品对SPP和非差非组合PPP的影响。更多还原

【Abstract】 Ionospheric delay is one of the main errors of GNSS navigation and positioning,which should be taken into consideration.The ionospheric model can correct the ionospheric delay for single-frequency users,and accelerate the convergence speed for double-frequency/multi-frequency users.Differential code bias is a subsidiary product of ionospheric grid.It not only affects the accuracy of ionospheric model,but also has significant influence on amending clock offset datum of integrated positioning with different observations.To meet the needs of engineering survey and scientific research,international satellite navigation service and analysis centers have been conducting research to improve the accuracy and timeliness of ionospheric products.Since 2018,Beidou Data Analysis Center of China University of Mining and Technology has been estimating global real-time ionospheric products.However,ionospheric products have not been released officially due to the internal testing stage.In this paper,the main contents and conclusions are as follows.(1)We introduced the basic theory of GNSS navigation and the theoretical methods for monitoring and modeling ionosphere in detail.Specifically,the combinational schemes of some commonly used linear observations,and their comparison in terms of application conditions and advantages or disadvantages are discussed;the advantages and disadvantages of two cycle slip detection methods in data processing are summarized and verified by experimental test;and the conventional methods and theories for ionospheric monitoring and modeling are introduced.(2)In this study,we proposed a multi-frequency differential code biases estimation method for BD-2 satellites based on closure difference constraint.The test results show that the differences are trivial between estimated multi-frequency differential code biases and those calculated by CAS.Due to the limitation of station conditions,the stability of DCB estimated by DCB and CAS in this paper is lower than that published by DLR.Besides,we analyzed the influence of DCB correction on the positioning results of different combinations of observations in different positioning modes.(3)This study explored the principle and method of global real-time ionospheric product in Beidou Data Analysis Center of China University of Mining and Technology.We compared the products against the final ionospheric product ‘whug’ from Wuhan University Analysis Center.Statistical results show that the accuracy of the real-time ionospheric products is equivalent to that of final products,and the difference is within 5 TECu,which meets the requirements of ionospheric products accuracy.Besides,we also analyzed the impact of real-time ionospheric products on standard single point positioning and undifferenced and uncombined PPP.更多还原