GNSS参考站网络的电离层完备性监测研究

本文基于四川GPS综合服务网络(SIGN)的计算结果表明:IRIM指标可用于衡量参考站网络内的电离层完备性监测的总体情况,IRIU指标提供了完备性监测信息在参考站网络中更为详细的空间分布情况,上述指标应用于参考站网络数据处理中心进行实时电离层完备性监测,能有效保证参考站网络内流动端用户定位的时间空间可用性和可靠性。     

广域差分GPS系统完备性监测

广域差分 GPS系统完备性监测技术是广域差分的关键和核心。本文全面介绍了完备性监测技术的定义 ,完备性监测系统的构成 ,以及各个部分的监测方法 ,包括监测站和用户站的监测技术 ,最后给出了完备性监测的一般步骤。     

广域差分GPS系统完备监测

广域差分ＧＰＳ系统完备性监测技术是广域差分的关键和核心。本文全面介绍了完备性监测技术的定义,完备性监测系统的构成,以及各个部分的监测方法,包括监测站和用户站的监测技术,最后给出了完备性监测的一般步骤。     

卫星导航完备性监测的最新进展

自从美国于2000年取消GPS SA政策并开始实施GPS现代化,以及欧洲伽利略导航系统正式开始启动以来,在完备性监测技术方面出现了许多新的发展和动向,本文将对其作简要的介绍。GPS和伽利略的完备性监测新技术主要包括:卫星自主完备性监测(SAIM)、星载和星间完备性监测、伽利略完备性能力评估(GIPA)的概念、用户自主完备性监测(UAIM)等。     

卫星自主完备性监测及其在提高GPS用户工作性能方面的应用

卫星自主完备性监测方法(SAIM)是将完备性监测功能直接设置于导航卫星之中,每个卫星的SAIM子系统只用于监测该卫星本身的测距信号(码、相位/信号、导航信息等),而不像广域增强系统(WAAS)、空基增强系统(SBAS)、地基增强系统(GBAS,LAAS)那样必须同步处理12颗或更多颗卫星的信息。因此SAIM可以在1s之内完成对该卫星信号的完备性监测,并向用户发出完备性监测信息。它可以满足几乎所有用户对完备性的要求,甚至不用任何增强也能满足民航部门CAT Ⅰ级精密进近的技术指标。对于完备性监测要求十分高的应用,例如民航CAT     

精密单点定位用户自主式完备性监测算法

精密单点定位PPP是当前GNSS高精度定位中的关键技术之一,使用的PPP采用扩展卡尔曼滤波估计,未知参数包括站点坐标,接收机钟差,对流层延迟以及虚拟未知数。在QR奇偶检校法的基础上,重点考察设计矩阵向量间的相关距离,将其作为粗差探测和识别的研究对象。通过向量相关距离时间序列,可以区分单个粗差和多个粗差的粗差集。提出精密单点定位的RAIM算法,解决了精密单点定位中的质量控制问题,使得多个粗差的识别更加清晰和快捷。     

广域差分GPS监测站的完备性监测

介绍了广域差分 GPS系统中监测站的监测作用 ,研究了监测站单点差分定位的方法 ,讨论了监测站粗差的检验及其分离的理论和数学模型 ,最后应用广域差分 GPS99’陆基长距离实验进行了数据的处理     

广域差分GPS监测站的完备性监测

介绍了广域差分 GPS系统中监测站的监测作用 ,研究了监测站单点差分定位的方法 ,讨论了监测站粗差的检验及其分离的理论和数学模型 ,最后应用广域差分 GPS99’陆基长距离实验进行了数据的处理     

基于IGS网络资源的完备性监测研究

本文从国际知名的高精度数据处理软件BERNESE软件入手,选择欧洲三个IGS跟踪站2002年1年的原始观测数据,应用IGS网络资源包括GPS精密星历,GPS精密钟差,地球自转参数文件,进行精密单点定位计算,讨论卫星轨道对完备性监测的影响,并将IGS跟踪站视为监测站和用户站,实现对IGS监测站和用户站的完备性监测。     

电离层延迟对单频GPS点的影响及改正方法研究

电离层延迟是单频GPS地面沉降监测点的最主要误差源,如何削弱该误差的影响是提高单双频混合地面沉降监测系统精度的关键。采用中国广州南沙单双频混合GPS地面沉降监测网数据进行处理分析,结果表明,在低纬度地区即使基线较短,电离层延迟对单频GPS监测精度影响仍然较大,影响程度随基线长度增加而增大,而且在时间域上有明显的季节性变化规律:2、3月份与8、9月份电离层影响较为显著。利用双频点数据从观测值域对单频点电离层延迟误差进行改正,监测精度提高了57%,改善效果明显。     

Brazilian active GNSS networks as systems for monitoring the ionosphere

This research shows the viability of using Global Navigation Satellite System (GNSS) stations from Brazilian active networks in monitoring the ionosphere. Various indexes of ionospheric irregularities and scintillation of GNSS signals, estimated in real-time and post-processed from GNSS data, are explored for this purpose. This way, an increase in the spatial resolution of ionospheric information is provided, allowing the generation of maps of scintillation and irregularities in observing the spatial and temporal behavior of the layer’s activity cycle, since the number of ionosondes, imagers, and radars is insufficient for monitoring the irregularities in Brazil. Experiments to evaluate the estimates of the indexes are performed for periods of high and low variability of electrons. Three Brazilian networks are used: the Brazilian Network for Continuous Monitoring (RBMC), the GNSS Active Network of Sao Paulo State (GNSS-SP), and CIGALA/CALIBRA. The results are compared with data from ionosondes and PolaRxS-PRO Septentrio receivers, proving compatible with moderate to high correlations. An analysis of the seasonal variation during the peak of solar cycle 24 is carried out. The maps allow identifying the displacement of ionospheric irregularities along the magnetic equator over Brazil, from northeast to southwest, starting at 7:00 pm and ending at 2:00 am local time. Real-time monitoring is carried out for the summer solstice in the southern hemisphere, and results are consistent with those from the post-processed mode. The indexes and maps can be applied to the analysis of GNSS positioning. Real-time ionospheric information can be used in important practical applications because the displacement monitoring of irregularities allows prior knowledge of whether there will be a deterioration of positioning accuracy in a certain region.     

Extreme value theory-based integrity monitoring of global navigation satellite systems

Measurements consistency-based Receiver Autonomous Integrity Monitoring (RAIM) is the main technique for monitoring the integrity of global satellite navigation systems at the user-level. Existing RAIM algorithms utilize two tests, in the position domain a test for RAIM availability and in the measurement domain a test for failure detection. These tests involve the computation of three parameters: test statistic, decision threshold, and protection level. The test statistic is based on the actual measurements in the form of the sum of the squared errors (SSE). The decision threshold is chosen on the basis of the statistical characteristics of the SSE including the assumption that the errors are normally distributed. However, in practice residual, error distributions exhibit heavier tails than predicted by the Gaussian model. Therefore, this paper challenges the normality assumption of the residual navigation errors in three ways. First, real data are used to assess its impact on the traditional RAIM algorithm. Second, extreme value theory is applied to the tails, and the generalized extreme value (GEV) distribution is derived to capture residual navigation errors. Third, the performance of the traditional RAIM approach is compared with that employing the GEV distribution. The results demonstrate that the GEV model is a more accurate representation of the distribution of residual navigation errors than the conventional Gaussian model and should be used in the development of integrity monitoring algorithms.     

基于多源数据的电离层异常监测及GNSS影响效应研究

电离层是日地空间环境的重要组成部分,电离层异常对无线电通讯和人类空间活动的影响不容忽视.电离层异常监测,在高精度GNSS PNT 服务与深空探测误差修正、空间天气预报预警及日地空间环境动态监测等方面具有重要科学意义和实用价值.海量地基、天基多源电离层观测数据,为电离层异常监测及电离层精细化时空变化反演提供了丰富的数据源.论文利用全球约250个Multi-GNSS站和COSMIC掩星观测数据,采用并行计算10 m in内实现全球数据处理,近实时构建了三维电子密度模型,融合掩星数据使得海洋地区的精度明显改善;搭建了天地联合多源电离层观测数据融合处理试验平台,在线提供近实时三维电离层产品,可为地球空间飞行器的空间环境信息支持、空间环境异常监测及预报、导航系统全球电离层延迟修正等提供服务.基于近实时三维电子密度模型,开展了电离层异常的立体监测,较IRI模型能够更好地监测磁暴期间电离层异常与演化过程,实现了全球大尺度、区域精细化电离层动态监测.同时,论文针对电离层异常对GNSS影响效应展开了较为全面的研究,分析了磁暴、太阳耀斑对GNSS信号、电离层模型精度、服务性能的影响.     

分布式WADGPS完备性监测技术研究

介绍了分布式WADGPS系统中监测站和用户站的监测方法，讨论了监测站和用户站的粗差探测与分离，最后应用分布式WADGPS99‘陆基长距离试验和南海海上试验进行了数据处理和分析。     

北斗不同电离层模型精度分析

目前北斗系统播发多种电离层模型参数,用户使用时容易产生以下问题:①同一历元不同卫星播发同一电离层模型,其值不完全相同;②北斗二号、北斗三号分别播发的Klobuchar电离层模型参数值存在差异;③对于能同时接收到3种电离层模型(BDS-2Klobuchar、BDS-3 Klobuchar及北斗全球电离层延迟修正模型(BDGIM))的基本导航用户如何选取合适的电离层模型。针对以上问题,本文首先提出采用最大投票法策略,对同一历元相同电离层模型但值不同的参数进行合理合并,然后以IGS分析中心的电离层产品为基准,对以上3种北斗电离层模型进行了精度分析和对比,最后基于等效距离误差进行了验证分析。试验结果表明,BDS-2 Klobuchar、BDS-3 Klobuchar虽然模型值差异较大但模型精度十分接近,而BDGIM模型精度最高,相对于前两者在中低纬地区平均提升10%,在两极地区的提升更加明显,平均提升61%。     

GLS完好性故障监测性能研究

卫星着陆系统(GLS)作为先进的航空新技术,其主要功能是为终端区精密进近的机载设备提供信号修正增强服务,为实现整个系统高精度离场和精密进近的功能发挥着重要作用. GLS完好性是终端区进近着陆引导应用的重要参数,是可靠性的重要依据,然而目前普通用户只关注导航定位的精度而没有考虑定位结果的可靠性,航空导航领域的机载对定位结果的可靠性要求极高,因此针对完好性故障监测性能展开研究分析,提出了一种接收机钟差调整策略并对其有效性进行仿真验证,并验证了完好性故障排除及未排除两种情况对定位精度及完好性的影响,进而证明完好性故障监测可保障GLS的系统性能、运行能力和安全性能达到预期要求.      

Carrier phase-based integrity monitoring for high-accuracy positioning

Pseudorange-based integrity monitoring, for example receiver autonomous integrity monitoring (RAIM), has been investigated for many years and is used in various applications such as non-precision approach phase of flight. However, for high-accuracy applications, carrier phase-based RAIM (CRAIM), an extension of pseudorange-based RAIM (PRAIM) must be used. Existing CRAIM algorithms are a direct extension of PRAIM in which the carrier phase ambiguities are estimated together with the estimation of the position solution. The main issues with the existing algorithms are reliability and robustness, which are dominated by the correctness of the ambiguity resolution, ambiguity validation and error sources such as multipath, cycle slips and noise correlation. This paper proposes a new carrier phase-based integrity monitoring algorithm for high-accuracy positioning, using a Kalman filter. The ambiguities are estimated together with other states in the Kalman filter. The double differenced pseudorange, widelane and carrier phase observations are used as measurements in the Kalman filter. This configuration makes the positioning solution both robust and reliable. The integrity monitoring is based on a number of test statistics and error propagation for the determination of the protection levels. The measurement noise and covariance matrices in the Kalman filter are used to account for the correlation due to differencing of measurements and in the construction of the test statistics. The coefficient used to project the test statistic to the position domain is derived and the synthesis of correlated noise errors is used to determine the protection level. Results from four cases based on limited real data injected with simulated cycle slips show that residual cycle slips have a negative impact on positioning accuracy and that the integrity monitoring algorithm proposed can be effective in detecting and isolating such occurrences if their effects violate the integrity requirements. The CRAIM algorithm proposed is suitable for use within Kalman filter-based integrated navigation systems.

基于IGS精密星历的完备性监测指标SISA研究

在卫星导航定位系统中,空间信号精度SISA是反映完备性参数的重要指标之一。从SISE与SISA的基本概念出发,描述了SISA的计算算法,根据卫星星钟的不同,选取了不同类型的GPS卫星,并利用IGS精密星历,预报精密星历进行了SISE和SISA的计算,结果表明:IGR星历计算的SISA指标满足系统要求,SISA主要受卫星钟差的精度影响,不同原子钟类型的卫星计算出来的SISA值变化不大。该成果对于卫星导航的完备性监测数据处理具有参考意义。