【作者】 袁玉斌；

【导师】 党亚民； 成英燕；

【作者基本信息】 中国测绘科学研究院 ， 大地测量学与测量工程， 2010， 硕士

【摘要】 精密单点定位(PPP, Precise Point Positioning)是最近几年发展起来的一项GPS定位新技术。该定位模式仅利用单台接收机即可联合IGS等组织提供的卫星星历和卫星钟差来进行分米级至厘米级精度的单点定位。这在实时精密导航、精密授时、国土资源调查以及航空摄影测量等领域均具有广阔的应用前景。本文围绕精密单点定位数据处理这一中心展开研究,介绍了其数学模型和大气延迟改正方法,最后用参数估计方法进行了静态定位和动态定位解算。本文对数据预处理的TurboEdit算法进行了较大改进。改进后宽巷模糊度及其方差的计算考虑了不同弧段、弧段长度、粗差影响等因素;两类组合观测值Melbourne-Wübbena(M-W)和Geometry-Free(G-F)均通过探测连续三个历元的状态来决定当前历元是否为周跳或粗差;设计了一个基于滑动窗口的拟合模型,该模型更符合G-F观测值的平滑时间序列特征;同时对划分的G-F弧段,可进行二次处理,进一步剔除小粗差。实验表明改进的算法可探测并精确修复等周、等距、连续周跳,对连续粗差和表现并不明显的粗差,亦能有效将其剔除。在误差改正方面,本文详细介绍了IGS的新版本天线文件igs05.atx及基于此文件将天线相位中心偏差改正到卫星/测站坐标或信号传播距离改正值的方法。另基于IGS及其分析中心发布的15min、30s、5s钟差产品,本文比较了Lagrange、Newton、三次样条等代数插值方法的精度,提出基于傅里叶变换和谱分析的最小二乘拟合法,该方法精度更高,同时适于钟差预报。对于相对论效应,本文推导了四类计算方法并以实验结果得出结论:在精密定位数据后处理中,固然可以利用精度极高的精密星历,但在一般的导航定位或实时精密单点定位中,即使利用导航电文的信息也可以有效消除相对论效应对定位的影响。由于用精密星历计算相对论效应时要求得到精度较高的卫星速度,本文并没有采用简单的中点方法,而是由辛普森积分推导了辛普森数值微分公式,并应用于卫星速度的计算。大气延迟是GPS定位的主要误差源。其中电离层延迟一般用双频改正模型,然而该模型只能消除一阶项的影响。本文从理论上探讨了利用地磁场数据消除电离层二阶项影响的途径。对流层延迟改正是GPS数据处理中一个较难解决的问题,一般方法是将其划分为干分量和湿分量,先用映射模型进行初步改正,再设置一个待估计的湿延迟参数。近年来不少学者陆续提出了新的映射函数,其中VMF1是公认精度最高的,也是IGS推荐的算法。本文介绍了GAMIT软件中的对流层模型设置以及GAMIT估计对流层天顶延迟和提取可降水量PW的途径,然后对中国地壳运动观测网络2008年的基准站数据进行了解算,并根据解算结果,多角度比较了三类高精度的对流层延迟映射函数:GMF、NMF和VMF1。在分析实验结果以及近一两年文献的基础上,选择精度最高的VMF1算法用于本文的精密单点定位模块。本文详细介绍了利用VMF1模型消除对流层延迟的数据处理流程。本文介绍了序贯最小二乘和扩展的卡尔曼滤波这两类参数估计方法,并应用于精密单点定位模块中。最后的实验结果表明,对于载波相位平滑伪距定位,测站位置误差的X , Y ,Z分量基本在±0.5m内;静态精密单点定位时即使利用15min钟差产品其定位精度也可达到厘米级;仿动态下定位精度为分米级,比静态情况下平滑伪距定位精度稍高些。本文还分析了粗差以及15min、30s、5s等不同采样率钟差产品对定位结果的影响,实验结果显著表明了粗差的剔除和高采样率钟差产品对提高定位精度的积极意义。更多还原

【Abstract】 GPS Precise Point Positioning (PPP) is a recently developed technique for GPS positioning, which makes use of single GPS receiver with precise ephemeris and satellite clock offset information from IGS, to get site coordinate accuracy of dm-cm level. PPP has proven to be effective and has received widespread acceptance in real-time navigation, precise time transfer, survey of land resource and aerial triangulation etc. This thesis focuses on PPP data processing, introducing its function model and statistic model, carrying out static and kinematic position solution with parameter estimation algorithms after error corrections.Three improvements of TurboEdit algorithm in GPS data preparation are presented in this thesis. In the improved algorithm, the calculating of wide-lane ambiguity and its variance takes into account different arc sections, the length of arc section and gross errors. Both combination observations determine whether the current epoch is a gross error or cycle slip by analyzing three successive epochs. A new fitting model based on sliding window is put forward, and the model is more suitable for the fact that Geometry-Free combination observations constitute a smooth time series. The secondary processing of divided Geometry-free arc sections further rejects gross error. Experimental results show that the new algorithm can detect and fix cycle slips of equal-distance, equal-cycle or continuing happened conditions. The new algorithm can also reject successfully successive gross errors and those gross errors with less obvious performance.This thesis introduces IGS’s new ANTEX (antenna exchange format) file igs05.atx as well as the algorithm to get correction of both site/satellite coordinates and signal propagation range bases on this file. As for satellite clock offset information of 15min, 30s or 5s interval from IGS, three common used interpolation methods are compared and experimental results show the three methods have similar effects while dealing with IGS precise satellite clock offsets. Considering clock offset variation characteristics, a new least square fitting model based on Fourier transformation and energy spectrum analysis is presented, which overcomes Runge phenomenon of high order polynomial interpolation. Experimental results indicate that this model solves two key problems while traditional algebraic polynomial models can not: first it performs the same accuracy at any time, at any sample rate; then the interpolation results are stable. This thesis presents four algorithms to get relative effect and experimental results show that we can easily get relative effect with GPS broadcast ephemeris. Troposphere delay is a troublesome problem in GPS data processing. The processing procedure of VMF1 model, which is recommended as the most accurate by IGS Workshop 2008, is presented in this thesis.For the number of involved equations and parameters waiting estimation is too huge, sometimes we even need kinematic positioning, the general Least Square algorithm is not suitable for PPP. This thesis presents Recursive Least Square and Extended Kalman Filtering, and the developed PPP module based on the two filters. Experimental results show that the accuracies of serial epoch positioning can be better than 50cm in X , Y ,Z component after initialization of about 15 minutes for PPP based on smoothed pseudorange. While the corresponding accuracies for PPP based on un-differenced dual-frequency pseudorange and carrier phase observations are cm level. In kinematic mode, the accuracies locate between the former two.With the developed PPP module, this thesis analyses positioning accuracies affected by gross error and different intervals of satellite clock offset. The results evidently prove the positive significance for PPP from gross error rejection and higher interval of satellite clock offset information.更多还原