毕业论文外文翻译-基于GPS的电离层监测及延迟的高精度改正的理论与方法的研究.doc

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1、中文翻译 摘要根据当前大地测量、地球物理、空间物理和导航等领域的科学研究和工程应用中的若干重要GPS科研项目的需要，近年来，我们系统研究了电离层延迟的高精度模拟和改正方法。本文报告的内容，是我们研究工作的部分贡献，主要涉及基于GPS的电离层监测及延迟的高精度改正的理论与方法的研究：如何通过修正静、动态单、双频用户的电离层延迟影响，进一步改善GPS 测量的精度和可靠性；增强型GPS广域差分系统的电离层模拟及利用GPS监测电离层的理论和方法等方面关键词：GPS的电离层监测，电离层延迟，GPS广域差分本文主要包括两方面的内容：一、研究背景的一般性描述及相关基础研究的系统总结和介绍,主要涉及：地球电离

2、层研究意义, 地球电离层探测技术与相关理论研究的内容,现代大地测量中电离层问题的由来、严重性与新课题, 地球电离层的基本特性及其对电波传播的影响，GPS定位的基本理论与方法，电离层延迟对GPS测量的影响，GPS的电离层延迟改正的基本方法，基于GPS的电离层研究的基本原理与方法等。进而论述了解决GPS的电离层延迟影响的重要性和切入点。二、具体研究工作的系统报告，主要集中在以下几方面: 研究如何利用单台双频GPS接收机的观测信息确定电离层延迟改正模型，为小范围的单频用户服务；研究如何实时分离GPS观测中的仪器偏差与电离层延迟；研究如何建立较大区域的电离层格网模型，进而初步设想利用中国地壳运动观测网

3、络深入研究我国领域的电离层的电子浓度变化规律；研究单频用户在不利条件下，如何更好地利用电离层延迟改正信息；研究利用GPS监测随机电离层扰动的基本理论和框架方案；研究如何综合顾及电离层的周日、季节和年变化，进一步提高利用GPS模拟电离层延迟的能力；研究如何实现星载单频GPS低轨卫星的精密测轨中的电离层延迟改正要求。1. (局部)电离层延迟的高精度提取系统论述和分析了影响利用GPS观测精确提取电离层延迟信息的各类因素。通过对有关模型和方法问题的深入研究，进一步提高了利用GPS提取电离层延迟信息的精度。主要包括：（1）将参数固定的三角级数函数电离层模型，扩展为更适用于理论研究和实际应用的参数可调型广

4、义形式，实现了根据电离层延迟时空变化特征，选择不同的特征参数模拟电离层延迟的影响。试算结果表明，它能较好地反映电离层活动特性，提高了局部电离层延迟模拟能力，适用于DGPS系统修正其服务区域内的单频GPS用户的电离层延迟。（2）设计了几种不同的计算方案，用于分析仪器偏差对确定电离层延迟的影响的特点。研究表明，仪器偏差对求解电离层延迟的影响远大于观测噪声的影响，给电离层延迟观测值带来高达数米的系统误差。利用GPS观测数据求解电离层模型或直接计算斜距电离层延迟时，都须慎重处理仪器偏差，不应简单把其作为噪声处理;（3）利用相位平滑测码数据进一步精化了仪器偏差分离方法，探讨了仪器偏差的稳定性。研究发现，

5、新方法可有效克服噪声对分离仪器偏差的影响，而且仪器偏差相对稳定并可有效进行测段间及数日间预报。（4）基于实时平均去噪和码、相位观测数据的加权联合处理的思想，提出了一种实时分离仪器偏差和求解电离层延迟量的新方案。算例表明，新方法通过采用平均去噪分离方法后处理相位平滑测码数据，求出仪器偏差并对需要实时处理仪器偏差的观测数据进行预报改正，直接利用观测值确定电离层延迟量，待估参数少、能消除仪器偏差的大部分影响，具有较好的精度，可作为WAAS及其他GPS网络系统确定电离层延迟的可行的参考方案。2. 一种构建大规模(区域性和全球性)高精度格网电离层模型的新方法站际分区法及其在中国的初步实现在系统深入研究了

6、格网电离层模型建立原理与方法的基础上，为避免基准站网的几何结构对模型精度估计的影响，充分顾及电离层延迟影响的局部特性，进一步提高格网电离层模型的构建精度，提出了一种新的格网电离层模型构建方法站际分区格网法。在以上研究的的基础上，估计了利用地壳运动观测网络的基准网建立格网电离层模型的精度，初步探讨中国域内拟建立的广域差分GPS增强系统，采用格网电离层模型提供电离层改正信息的可行性及有待进一步研究的问题。3. 不利条件下为WAAS的单频GPS用户提供电离层延迟改正的新方法APR-I方案在正常条件和平静电离层区域，WAAS能够满足单频用户的电离层延迟改正要求，但当用户无法正常获取电离层延迟改正信息时

7、，如在差分系统突然中断信息发送或用户步入无法正常接收差分改正信息的位置等不利条件下，单频GPS接收机不能有效进行实时电离层延迟改正，尤其在电离层活动异常区域如电离层扰动条件下，实时差分改正效果将受到严重影响。这些问题在WAAS的实际运行中是难以避免和必须解决的。而以往的研究结果，均为后处理方法，不能满足(准)实时处理电离层扰动的要求。针对这种状况，我们通过设计能有效结合电离层延迟绝对量和相对变化量的抗差递推过程，提出了一种可在以上不利条件下有效实时改正单频GPS用户电离层延迟的方法APR-I方案。1）构建APR-I方案的理论依据WAAS正常运转和正常条件下可提供高精度的电离层延迟改正信息(绝对

8、量)，而WAAS所服务区域内的单频GPS接收机在不利条件下也能有效提供电离层延迟变化量(相对量)，且在不考虑噪声影响，可直接计算任意两观测历元间的电离层变化量的近似值。2）提出APR-I方案通过设计能有效结合电离层延迟绝对量和相对变化量的抗差递推过程，研究了一种新的单频GPS电离层延迟改正方案(称为APR方案,即Absolute Plus Relative Scheme)；给出了APR-I方案的精度估计公式；分析实施APR-I方案的有效途径。研究表明，新方案既保留正常条件下差分电离层延迟信息的精确改正效果，也确保了在不利条件下单频GPS用户的电离层延迟改正效果。APR-I方案的实施，不需改变W

9、AAS原有的整体设计思想，对硬件无新的要求，只需对用户GPS软件稍加改进，实施简便，是WAAS和单频GPS用户均可接受和易于实现的。4. 检测随机信号的新理论变样本自协方差估计的提出及其在GPS监测随机电离层扰动中的应用根据GPS时序观测的特点，通过设计先研究样本时序变化时随机电离层折射的自协方差估计的统计特性，再探讨利用GPS实时监测电离层活动的新方法的思路，从基础理论的提出到框架方案的建立，系统深入研究了利用GPS监测随机电离层扰动的基本理论与方法。具体包括：1）研究变样本自协方差估计(ACEVS)理论从一般的数学意义上建立了ACEVS的基本模型，并在进一步扩展白噪声理论的基础上，得到了A

10、CEVS估计的理论和简化解式，即变样本自协方差估计的统计模型参数估计解式，进而建立了随机信号扰动的诊断准则。2）ACEVS估计应用于GPS电离层监测的可行性的理论证明与模拟分析不仅从理论上证明了ACEVS应用于GPS电离层监测的可行性，而且利用双频GPS数据也成功地模拟了随机电离层折射的ACEVS估计的特性，并发现，变样本自协方差估计的统计特性对随机电离层延迟变化是敏感的；初步讨论和分析了GPS观测提供的TEC变化也适用于ACEVS方法应用条件.3）建立利用GPS监测随机电离层扰动的框架方案综合ACEVS理论及相关的结论和GPS时序采样的特点，初步给出一种基于GPS的电离层扰动监测的框架方案。

11、以上方法尽管是针对实时监测要求提出的，但它完全可用于后处理情况。电离层扰动的GPS探测方案，主要分后处理和实时两种情况，静、动态实时方案基本相同，差别主要取决于硬件要求。试验结果表明，利用ACEVS研究基于GPS的随机电离层活动的监测方法的设想是基本可行的；所给出的框架方案可作为设计各类利用单台(静、动态)双频GPS接收机监测电离层活动的方法的参考方案之一。5. 利用GPS数据精确模拟电离层延迟的新构想电离层蚀因子法及初步实现提出了IPP点的电离层蚀因子及其影响因子的概念，给出了简便的计算方法，进而提出了一种利用GPS数据确定电离层延迟改正模型的新方法电离层蚀因子法。电离层蚀因子及其影响因子，

12、能够根据电离层随周日、季节、半年和周年的变化，将适应于不同季节的电离层延迟模型有效结合起来。研究表明，利用蚀因子法模拟的电离层延迟的改正精度与利用电离层无关观测的消除电离层延迟的精度很接近，使得单频GPS观测的电离层延迟的改正精度有望实现突破性提高，从而接近双频GPS观测自校正电离层延迟的精度。同时，由于它具有很好的描述和区分电离层日间和夜间的能力，所以很适合模拟高动态低轨卫星的星载单频GPS观测数据的电离层延迟的变化特性。6. 高精度修正星载单频GPS低轨卫星的电离层延迟的新对策APR-II方案，即空基APR方案分析了现有方法无法保证高精度和高可靠性地进行电离层分层这一严重不足；利用实测数据

13、模拟全球电离层模型和建立高精度区域格网电离层模型，初步分析了在全球范围内寻找若干个电离层结构和活动相对较有规律的局部区域的可行性；设计了在选定的局部电离层区域，联合处理地基和低轨空基用户的GPS观测数据有效进行电离层分层的具体方法，给出了相应的精度估计公式。初步的精度估算和试算结果表明，这种在局部区域进行有效电离层分层的设想及给出的实施方法是可行的。进而系统性地提出了一种用于星载单频GPS接收机精密测轨中电离层延迟改正的综合方法APR-II方案。地面GPS数据进行的两个初步模拟计算结果显示，利用APR-II可满足低轨卫星等低轨航天器精密测轨时的电离层延迟的高精度改正要求。外文原文Abstrac

14、tRecently, according to the requirements of some important GPS research subjects in the fields of Geodesy, Geophysics, Space-Physics and navigation in China, we studied systematically how to correcting the effects of the ionosphere on GPS, with high-precision and accuracy. As the parts of the main c

15、ontributions, the research projects focus mainly on how to improve GPS surveying by reducing ionospheric delay for dual/single frequency kinematic/static users: high accuracy correction of ionospheric delay for single/dual frequency GPS users on the earth and in space, China WAAS ionospheric modelin

16、g and the theory and method of monitoring of ionosphere using GPS. KEYWORDS:GPS ionospheric monitoring, ionospheric delay, GPS Wide Area DifferentialThe main contents of this Ph.D paper consist of two parts:Fisrt part-the outline of research background and the systematic introduction and summarizati

17、on of the previous research results of this work. Second part-the main contribution and research results of this paper are focused on as follows:(1) How to use the measurements of a dual frequency GPS receiver to determine the ionospheric delay correction model for single frequency GPS of a local ra

18、nge;(2) How to separate the instrumental biases with the ionospheric delays in GPS observation;(3) How to establish a large range grid ionosphere model and use the GPS data of Chinese crust movement observation network to investigate the change law of ionospheric TEC of China area; (4) How to improv

19、e the effectiveness of correcting ionospheric delays for WAASs users under adverse conditions.(5) How to establish the basic theory and the corresponding framework of monitoring the stochastic ionospheric disturbance using GPS(6) How to improve the modelling ability of ionospheric delay according to

20、 its diurnal, seasonal, annual variations based on GPS;(7) How to meet the demand of correcting the ionospheric delay of high-precision orbit determination for low-earth satellite using a single frequency GPS receiver1Extracting (local) ionospheric information from GPS data with high-precision The f

21、actors are systematically described and analyzed which limit the precision of using GPS data to extract ionospheric delays. The precision of determining ionospheric delay using GPS is improved based on the further research of the related models and methods. The main achievements of this work include

22、 the some aspects as follows:(1) Based on a simple model with constant number of parameters, which consists of a set of trigonometric series functions, a generalized ionospheric model is constructed whose parameters can be adjusted. Due to the property of selecting the different parameters according

23、 to the change law of ionospheric delay, the new model has better availability in the field of the related theoretic research and engineering application. The experimental results show that the model can indicate the characteristic of ionospheric actions, improves further the modeling ability of loc

24、al ionosphere and may be used to correct efficiently ionospheric delay of the single frequency GPS uses serviced by DGPS. (2) Different calculating schemes are designed which are used to analyze in detail the characteristics of the effect from instrumental bias (IB) in GPS observations on determinin

25、g ionospheric delays. IB is different from noise in GPS observations. The experimental results show that the effect of IB is much larger than that of the noise on estimating ionospheic delay, and IB can cause ionospheric delay measurements to include systematic errors of the order of several meters.

26、 Therefore, one must significantly take notice of IB and remove its negative effect, and should not casually consider IB as part of noise whenever GPS data are used to fit ionospheric model or to directly calculate ionospheric delay.(3) Stability of IB is studied with a refined method for separating

27、 it from ionospheric delay using multi-day GPS phase-smoothed code data. The experimental results show that, by using averaging of noise with phase-smoothed code observation，the effect of noise on separating IB from ION can be efficiently reduced, and satellite bias plus receiver bias are relatively

28、 stable and may be used to predict the IBs of the next session or even that of the next several days.(4) A new algorithm about static real time determination of ionospheric delay is presented on the basis of the predicted values of IB and the technique of real time averaging of noise and weighted-ad

29、justment of dual P-code and carrier phase measurements. The preliminary results show that the new method, which is by post-processing phase-smoothed code data to calculate the IB and then with them to predict and to correct the IB of data needed to remove its effects in real time in the next observa

30、tion periods, has relatively better accuracy and effectiveness in estimating ionospheric delay. It is very obvious that the scheme can relatively decrease the number of unknown parameters, can efficiently reduce the main negative effect from instrumental bias, and can be easily used to directly and

31、precisely determine ionospheric delay with dual-frequency GPS data. Hence, the method may be considered as an available scheme to determine ionospheric delays for WAAS and many other large range GPS application systems.2 A method of constructing large range (regional and global) high-precision grid

32、ionospheric modelthe Different Area for Different Stations (DADS) and its application in ChinaBased on the systematic and further research of the principle and methods of establishing grid ionospheric model (GIM), a new method of establishing a GIM - Different Areas for Different Stations (DADS) is

33、investigated which is advantageous for considering the local characters of ionosphere, avoiding the effects of the geometrical construction of GPS reference network on estimating the external precision of the GIM, and improving the precision of calculating model parameters. The above results are use

34、d to make a preliminary estimation of the latent precision that can be obtained by establishing a large range high precision grid ionospheric model based on the Chinese crust movement observation network, and to investigate the possibility that the GIM provides high-precision ionospheric correction,

35、 and to identify the relevant problems which need to be solved for the planned GPS Wide area Augmentation System (WAAS) of China.3 A method of efficiently correcting ionospheric delays for WAASs users under typical adverse conditions the Absolute Plus Relative Scheme (APR-I)The commonly used WAASs D

36、IDC received by single frequency GPS receivers can usually provide the effective correction of the ionospheric delays for the users under normal conditions and in the fields of calm ionosphere. However, the ionospheric delays cannot be efficiently accounted for during those periods when the WAAS can

37、not broadcast the DIDC values to users, or when the receivers cannot receive the DIDCs for whatever reason. The ionospheric delay corrections will be less well known in cases when the variations of the ionospheric delays may be very large due to ionospheric disturbances. The above difficulties canno

38、t be avoided to be encountered and must be solved for the WAAS.For this, a new ionospheric delay correction scheme for single frequency GPS datathe APR-I scheme is proposed which can efficiently address the above problems. 1) The theoretic basis of constructing the APR-I Scheme The WAAS can provide

39、high-precision absolute ionospheric delay estimates when it operates properly. Meanwhile, a single frequency GPS receiver serviced by the WAAS can efficiently determine the relative variation of the ionospheric delays between two arbitrary epochs even under adverse conditions if without considering

40、observation noises. 2) On the APR-I SchemeBased on a robust recurrence procedure and an efficient combination approach between absolute ionospheric delays and ionospheric relative changes, the APR-I scheme is present which is an new method of correcting ionospheric delay for single frequency GPS use

41、r. The formula of estimating the precision of the APR-I scheme is given. An implementation approach of the APR-I scheme is analyzed as well.The experimental results discussed above show that the APR-I scheme not only retains the characteristic of high accuracy of the DIDC from the WAAS under normal

42、ionospheric and reception conditions, but also has relatively better correction effectiveness under different abnormal conditions. The implementation of this method need not change the present basic ionospheric delay correction algorithm of the WAAS. In addition, the APR-I method does not impose new

43、 demands on receiver hardware, and only requires a few improvements to receiver software. Hence it can be easily used by single frequency GPS users.4 A new theory of monitoring the random signal Auto-Covariance Estimation of Variable Samples(ACEVS) and its application in using GPS to monitor the ran

44、dom ionosphere A new approach for monitoring ionospheric delays is found and developed, based on the characteristic of time series observation of GPS, an investigation of the statistical properties of the estimated auto-covariance of the random ionospheric delay when changing the number of samples i

45、n the time series, the development of the related basic theory and the corresponding framework scheme, and the further research of using GPS and the above research results to study ionosphere.The concrete work is as follows:1) Studied the Auto-Covariance Estimation of Variable Samples (ACEVS) From a

46、 general mathematical aspect, the basic model of ACEVS is established. The theoretic and approximate solution formulas for ACEVS are derived based on the improvement of theory of white noise and then a test raw of the state of a random signal is established based on ACEVS;2) Verified and modeled the

47、 possibility of using ACEVS to test the change of state of stochastic delaysThe possibility of using ACEVS to monitor ionosphere is verified in terms of theory. Also it is found that the statistical property of ACEVS is sensitive to the change of the random ionospheric delay, on the basis of modelin

48、g the characteristics of ACEVS using a dual frequency GPS receiver. The application conditions of using ACEVS to monitor the variation of TEC extracted by GPS data are preliminarily discussed and analyzed as well.3) Established a preliminary framework scheme of using GPS to monitor the disturbance of random ionospheric delay.According to ACVES and all other results of the above and the characteristic of the time series observations of GPS, a preliminary framework scheme for monitoring the disturbance of random ionospheric delay u