基于区域CORS增强的实时PPP关键技术研究

发布时间：2018-03-10 10:11

本文选题：GNSS　切入点：PPP　出处：《东南大学》2016年博士论文　论文类型：学位论文

【摘要】：近年来,GNSS技术蓬勃发展,引发了导航定位领域的深刻变革,其应用领域日益扩大,已广泛服务于大地测量、空间科学、地球物理等领域。面对高精度、实时化GNSS应用需求的逐步增多,相关算法的探索创新和系统研发设计将面临新的机遇和挑战。对于PPP技术,初始化时间较长和受制于外部卫星的钟差与轨道是两大限制实时PPP应用的瓶颈。本文从PPP的内部理论算法入手,针对数学模型、系统误差处理等问题展开深入研究,通过结合区域CORS数据提供的增强信息,解决了PPP解算的实时性、快速性与自主性问题。主要内容及成果包括：1.优化了PPP观测方程的的数学模型与方法系统研究了PPP的理论算法,其中包括函数模型与随机模型。分析总结了PPP观测方程数学模型的发展现状,为提高PPP的收敛速度与定位精度,提出了改进方案：(1)提出了基于星间组合差分的PPP函数模型,既消除了部分未知参数,提高了数据解算效率,同时改进了卡尔曼滤波的未知数和协因数阵初值的精度,而且避免了引入不同观测值之间的相关性,实验证明收敛时间较非差模型提高了30%。(2)顾及了载噪比指标对观测值随机误差的影响,在高度角随机模型基础上,引入载噪比缩放因子,更准确地反映了系统状态,补偿了系统随机误差对未知参数估计的影响,实验证明收敛至分米级精度所需时间明显缩短,比高度角模型缩短了36%。2.精化了对流层延迟经验模型从气象参数、天顶延迟和映射函数三个方面出发,改进并融合出一种新的全球对流层延迟改正模型SEUTROP。与原有模型相比,SEUTROP的优势体现为：(1) SEUTROP模型应用了全球格网气象参数,在时间尺度和空间尺度上更能反映出对流层延迟的变化,相比标准气象参数的计算结果,精度提升了一个数量级。(2)与现有模型(以UNB3m为例)相比,SEUTROP模型在全球范围的精度更均匀,在南半球(尤其是南极洲)区域的精度优势尤其明显,在北半球冬季表现更好。3.建立了基于IGS产品的实时PPP模式用于实时PPP的IGS产品可分为两类,一类基于IGU产品做外推预报,另一类基于Ntrip协议传输实时产品。(1)IGU预报轨道和钟差的精度差异很大。卫星轨道连续可导,因此外推算法对轨道的精度损失不大,外推9小时的轨道误差在5cm以内；但卫星钟差具有离散性与随机性,插值算法导致钟差误差普遍在10ns附近波动,不满足实时PPP的精度需求。(2)IGS实时服务通过计算精密星历轨道与钟差相对广播星历的改正量,并基于Ntrip协议实时播发给用户。其中精密轨道误差在2cm至4cm范围内波动,优于IGS给出的精度指标：卫星钟差约0.3ns,相比IGU预报钟差精度得到显著提升；此外,所有的实时产品的数据完整性约95%,数据时延约为30s,满足准实时PPP的应用需求。基于IGS实时产品实现了准实时精密单点定位,定位效果与事后模式相当。4.完善了区域CORS增强PPP的理论和应用从理论推导和实验分析两方面验证了区域CORS反演定位增强信息的可行性,完善了区域CORS的服务体系,充分发挥了区域CORS的潜在价值。反演的增强信息主要包括：(1)基于稀疏的区域CORS参考站网,实现了实时卫星钟差的快速估计。通过固定卫星轨道,理论上单台地面跟踪站即可实现钟差反演,区域CORS多参考站加权的联合估计算法增强了估钟结果的可靠性与稳定性。为了实时快速估计高采样率钟差,在星间差分估计低采样率钟差的基础上,通过星间-历元间二次差估计钟差的历元间变化,以累加的形式快速还原高采样率卫星钟差,得到优于0.2ns精度的卫星钟差,与IGS提供的精密钟差的精度持平。(2)提出参考站的ZTD提取及区域建模方法。以静态PPP的方式反演区域CORS参考站的ZTD,精度能够达到毫米级。顾及高程对ZTD的影响,区域建模至少需要4个参考站,通过空间回归模型内插流动站用户ZTD,在参考站网内和周边区域的用户对流层建模精度可达到毫米级。(3)基于区域CORS实现UPD分离,进而获得PPP模糊度固定解。在参考站以“宽巷-无电离层-窄巷”的经典三步法计算卫星UPD的小数部分FCBs,流动站用户通过接收卫星UPD信息固定卫星模糊度,使PPP解算更稳定。流动站通过接收区域CORS增强信息实现了PPP快速解算,收敛速度提高30%。5.提出了基于耦合钟差的自主PPP算法利用本文提出的区域CORS钟差快速估计技术,以广播星历替代精密星历计算卫星位置,提出完全自主的PPP算法,并且将区域CORS的精密定位服务范围向网外延伸了500km。该算法创新性包括：(1)从理论推导和实验分析两方面验证了卫星轨道误差和卫星钟差的耦合关系,两者可作为统一参数进行估计,区域CORS网内参考站的实验表明耦合估计对定位误差方程OMC向量的影响在毫米级；(2)传统CORS提供的定位服务局限于参考站覆盖范围之内,对于流动站跨网元连续作业以及超出覆盖区域(如近海区域)的解算较困难。基于广播星历的实时PPP技术不但实现了解算数据完全自主提供,而且对于网内、网外测站的点位精度分别提高了38.8%和36.1%,收敛速度则分别提高了61.4和65.9%。在全球化PPP服务实现之前,该算法可作为一种替代方案实现了区域定位服务。(3)在缺少BDS精密星历的情况下,率先实现了基于BDS的PPP,单天解平面定位精度约lcm,与基于GPS的PPP结果一致；在高程方向上精度约10-20cm,精度较差的主要原因在于卫星与接收机的天线参数不明确。
[Abstract]:In recent years, rapid development of GNSS technology, led to profound changes in the field of navigation and positioning, its application field is expanding, and has been widely used in geodesy, space science, earth physics and other fields. In the face of high precision, real-time GNSS application needs to increase gradually, research and design exploration innovation and system related algorithms will face new the opportunities and challenges. As for the PPP, initialization time is too long and subject to the external clock and satellite orbit is two limits of real-time PPP applications bottleneck. This article from the internal theory of PPP algorithm, according to the mathematical model, studies the system error handling and other issues, through enhanced information combined with regional CORS data. To solve the real-time computation of PPP, fast and independent problems. The main contents and results are as follows: 1. optimization of the PPP observation equation mathematical model and method of the system of the theory of PPP The algorithm, which includes function model and stochastic model. Analyzed and summarized the development situation of PPP observation equation mathematical model, in order to improve the convergence speed and the precision of PPP, put forward the improvement scheme: (1) the inter satellite combination difference model based on PPP function, which eliminates part of unknown parameters, improve the efficiency of the data calculation, we also improved Calman filter of unknowns and the coordinated factor matrix initial accuracy, but also avoid introducing different correlation between the observations and the experiments show that the convergence time is non difference model improved by 30%. (2) takes into account the effect of random error of carrier to noise ratio index of observation, in the high angle based on stochastic model introduction, CNR zoom factor, more accurately reflects the state of the system, the system compensation effect of random errors of unknown parameter estimation, the experiments show that the convergence to decimeter level precision were shortened and high Angle model shortens 36%.2. refinement of the tropospheric delay experience model from three aspects of meteorological parameters, zenith delay and mapping function of improvement and integration of a new global tropospheric delay correction model of SEUTROP. compared with the original model, the advantages of SEUTROP are: (1) SEUTROP model is applied to the global grid more meteorological parameters. Can reflect the change of the tropospheric delay in the time scale and spatial scale, the calculation results compared to standard meteorological parameters, improve the accuracy of an order of magnitude. (2) with the existing model (such as UNB3m) compared to the SEUTROP model is more uniform in the global scope of the accuracy in the Southern hemisphere (especially Antarctica) precision regional advantage is particularly evident in the northern hemisphere winter, better.3. established a real-time PPP model based on IGS for real-time PPP IGS products can be divided into two categories, one kind of extrapolation forecast based on IGU products And another kind of transmission based on Ntrip protocol in real-time products. (1) the difference of IGU forecast accuracy of orbit and clock greatly. The satellite orbit continuously differentiable, so extrapolation method to track the little loss of accuracy, extrapolation of 9 hours in orbit error is less than 5cm; but the satellite clock error is discrete and stochastic interpolation. The algorithm leads to clock in the vicinity of 10ns common error fluctuations, does not meet the accuracy requirement of real-time PPP. (2) IGS real time service by calculating the precise ephemeris orbit and clock error correction of the broadcast ephemeris, and based on the Ntrip protocol and real-time broadcasting to the user. The precise track error in the range of 2cm to 4cm range, precision index better than IGS given: satellite clock error is about 0.3ns, compared to the IGU prediction of clock precision has been significantly improved; in addition, the integrity of the data real-time all products of about 95%, the time delay of the data is about 30s, meet the application requirements. The quasi real time PPP based on IGS Real time products can realize quasi real time precise point positioning, positioning effect and improve the regional.4. model after CORS from theoretical derivation and experimental analysis verify the two aspects of regional CORS enhanced the feasibility of information inversion theory and application of PPP increased, improve the regional CORS service system, give full play to the potential value of regional CORS the enhancement of information. Inversion mainly includes: (1) regional reference station network based on sparse CORS, to achieve a rapid estimation of real-time satellite clock error. By fixing the satellite orbit, the theory of single ground tracking station clock error inversion can be CORS, the regional joint estimation algorithm of multi reference station weighted enhanced the reliability and stability. The clock. In order to real-time estimate of high sampling rate in the inter satellite clock error, differential estimation of low sampling rate based on the clock, through inter satellite - epoch two time difference estimation clock epoch In the form of rapid change, cumulative reduction of high sampling rate is better than the accuracy of 0.2ns satellite clock error, satellite clock error, flat precision clock and IGS provide poor accuracy. (2) proposed ZTD extraction and modeling method of regional reference station. In static PPP inversion region CORS reference station ZTD, accuracy at millimeter level. Take into account the impact of elevation on ZTD, regional modeling requires at least 4 reference stations, the spatial regression model interpolation in the mobile station user ZTD, user modeling precision reference station network in the troposphere and the surrounding region can reach millimeter level. (3) the CORS UPD region and PPP separation based on Fuzzy the degree of fixed solution. The classic three step in the reference station to "wide lane - - lane ionosphere free" satellite UPD calculation of the fractional part of FCBs, the mobile station user by receiving satellite information UPD fixed satellite ambiguity, the PPP solution is more stable. The flow through the grounding station Collect information to achieve PPP CORS enhanced regional fast calculation, increases the rate of convergence 30%.5. proposed PPP algorithm independent coupling clock error using the proposed region CORS clock estimation technique based on broadcast ephemeris to replace the precise ephemeris calculation of satellite position, put forward the PPP algorithm completely independent, and range of precision positioning service area CORS to extend the network innovation 500km. this algorithm includes: (1) from the theoretical and experimental analysis of two aspects to verify the coupling relationship between satellite orbit error and satellite clock error, both of them can be used as a unified parameter estimation, regional CORS network reference station experiments show that the coupling estimation of positioning error vector in equation OMC mm level; (2) the traditional positioning service provided by CORS limited to reference station coverage, for the mobile station across the ne continuous operation and beyond the coverage area (such as near the sea area) The solution is difficult. The technology of real-time PPP broadcast ephemeris is not only to achieve a completely independent data based, but also for the network, network tracking station point accuracy are improved by 38.8% and 36.1%, the convergence rate was increased by 61.4 and 65.9%. in the global PPP service before, this algorithm can be used as a the alternative to achieve regional positioning service. (3) in the absence of BDS precise ephemeris case, first to realize the BDS PPP based on single day solution plane positioning accuracy is about LCM, and based on the results of GPS PPP; in the elevation direction accuracy is about 10-20cm, the main reason lies in the poor precision of satellite and receiver antenna parameters is not clear.

【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P228.4

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