【作者】 蔡昌盛；

【导师】 高井祥；

【作者基本信息】 中国矿业大学 ， 大地测量学与测量工程， 2008， 博士

【摘要】 GPS精密单点定位是最近几年发展起来的一项卫星定位新技术,它利用精密卫星轨道和卫星钟差产品、双频测码伪距和载波相位观测值进行单台接收机定位,它可以在全球范围内进行作业并直接获得厘米级精度的ITRF框架坐标。与相对定位相比,它具有不受测站间观测距离限制、直接获得测站坐标、数据处理简单等优点。因而在区域高精度坐标框架的维持、科学考察、高精度动态导航定位及近地卫星的定轨、高精度工程测量、国土资源调查等方面都具有广阔的应用前景。但GPS作为一种基于卫星的导航定位系统,它的定位精度和可靠性在很大程度上依赖于观测到的卫星数量。在一些地方诸如城市峡谷、山区、露天矿区,可见卫星的数量常常不足以获得位置解。一种很好的解决办法就是组合GPS和GLONASS。随着GLONASS精密星历和卫星钟差数据产品的出现,组合GPS/GLONASS精密单点定位已成为可能。本文首先比较了GPS和GLONASS这两种卫星定位系统,然后对GPS和GLONASS这两种卫星系统在精密单点定位中涉及到的误差源及其处理方法进行了讨论,对于精密单点定位而言,除了需要考虑一般的误差如卫星轨道误差、卫星钟差,电离层延迟误差,对流层延迟误差,接收机钟差,多路径误差和观测噪声外,还需要考虑一些特殊误差源的影响。这些误差源包括卫星和接收机天线相位中心偏差,相对论效应,天线相位缠绕,固体潮,大洋负荷,大气负荷,塞格纳克效应等。本文详细阐述并比较了GPS精密单点定位中的两种模型即传统模型和P1-P2-CP模型,对观测值的随机模型和参数的随机模型进行了讨论。论文还给出了精密单点定位在卡尔曼滤波实现时进行质量控制的方法。由于GPS和GLONASS这两种卫星定位系统存在着时间系统的差异,因而当前的GPS精密单点定位模型无法处理GLONASS数据。本文对当前GPS精密单点定位的两种模型进行了拓展,推导出了GPS/GLONASS组合精密单点定位的观测模型和随机模型。组合模型包括组合GPS/GLONASS传统模型和组合GPS/GLONASS P1-P2-CP模型。为了对组合GPS/GLONASS精密单点定位模型进行评价,利用IGS跟踪站的观测数据和IAC(Information-Analytical Centre)的卫星精密星历和钟差数据,对组合GPS/GLONASS传统模型和组合GPS/GLONASS P1-P2-CP模型进行了试算。试算结果表明两种模型估计获得的三维位置精度,接收机钟差值、天顶方向对流层湿延迟都非常接近。为了进一步评价GPS/GLONASS组合精密单点定位的性能,利用了4个IGS测站的观测数据从位置解的收敛速度和收敛后位置解的精度两方面比较了GPS/GLONASS组合精密单点定位和单独GPS精密单点定位静态和动态模式下的定位结果。经比较发现,当观测到的GPS卫星数目较多并且卫星分布合理时,增加GLONASS观测数据对定位精度和位置解收敛时间影响不大。当观测到的GPS卫星数目较少时,GPS/GLONASS组合精密单点定位相比GPS精密单点定位能显著的提高位置解收敛后的定位精度和明显缩短收敛时间。更多还原

【Abstract】 GPS Precise Point Positioning (PPP) is a new satellite positioning technique in which precise satellite orbit and clock data, dual-frequency pseudo-range and carrier phase observables from one receiver are used to determine the position solution. PPP can be conducted globally and ITRF coordinates with centimeter-level accuracy can be achieved directly. In comparison with relative positioning, PPP has a few advantages such as no restriction by the inter-station distance, direct determination of position solution and simple data processing. As a result, PPP is widely applied to the maintenance of high-accuracy reference frame, scientific investigation, high-accuracy kinematic navigation and positioning, orbit determination of low orbit satellites, high-accuracy engineering survey, land resource investigation and so on. However for such a satellite-based navigation and positioning system, the positioning accuracy and the reliability of positioning results are quite dependent on the number of visible satellites. In some situations such as urban canyons, open-pit mines and mountainous areas, the number of visible satellites is insufficient to provide a position solution. A good strategy is to integrate GPS and GLONASS.Since the availability of GLONASS precise ephemeris and clock products, the combined GPS/GLONASS precise point positioning has become possible. In this thesis, the main research contents are as follows. Firstly GPS is systematically compared to GLONASS. Secondly error sources and corresponding handling methods are discussed for both GPS and GLONASS. On one hand, some conventional error sources such as satellite orbit error, satellite clock error, ionospheric delay error, tropospheric delay error, receiver clock error, multipath error and noise need to be considered. On the other hand, some special error sources such as satellite and receiver antenna phase center offsets, relativistic effects, phase wind up, earth tide, ocean loading, atmosphere loading and Sagnac effect also need to be taken into account. Thirdly, traditional PPP model and P1-P2-CP PPP model are introduced in detail, and their corresponding stochastic models of observations and unknown parameters are discussed.The quality control method in the Kalman Filter processing is also given. Fourthly, since the existing PPP models could not process the combined GPS/GLONASS data due to the system time difference between GPS and GLONASS, the combined GPS/GLONASS PPP models have been developed, which include combined GPS/GLONASS traditional model and P1-P2-CP model.To assess the performance of the combined GPS/GLONASS PPP models, the observation data from IGS, precise satellite orbit and clock data from IAC (Information-Analytical Centre) are used to conduct numerical computation. The three-dimension positions, a receiver clock, a system time difference unknown and zenith wet tropospheric delay unknown are estimated and almost the same results are obtained from the combined GPS/GLONASS traditional model and P1-P2-CP model. Further investigation results obtained in static and kinematic modes indicate that adding GLONASS observations does not have a significant impact on positioning accuracy and convergence time when sufficient GPS satellites are available. In contrast, the positioning accuracy and convergence time could be significantly improved using the combined GPS/GLONASS PPP models when the number of GPS satellites is insufficient or GPS satellite geometry is poor.更多还原