1、 第一篇 中英文互译 外文原文 Recently, 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 part
2、s of the main contributions, 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 iono
3、spheric modeling and the theory and method of monitoring of ionosphere using GPS. The main contents of this Ph.D paper consist of two parts: Fisrt part-the outline of research background and the systematic introduction and summarization of the previous research results of this work. Second part-the
4、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 range； (2) How to separate the instrumental biases with the ionosph
5、eric 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 improve the effectiveness of correcting ionospheric delays for WAASs
6、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 its diurnal, seasonal, annual variations based on GPS； (7) H
7、ow to meet the demand of correcting the ionospheric delay of high-precision orbit determination for low-earth satellite using a single frequency GPS receiver 1 Extracting (local) ionospheric information from GPS data with high-precision The factors are systematically described and analyzed which lim
8、it 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 the some aspects as follows: (1) Based on a simple model
9、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 to the change law of ionospheric delay, the new model ha
10、s 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 local ionosphere and may be used to correct efficiently iono
11、spheric 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 determining ionospheric delays. IB is different from noise in GPS o
12、bservations. 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. Therefore, one must significantly take notice of IB and
13、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 it from ionospheric delay using multi-day GPS phase-smo
14、othed 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 stable and may be used to predict the IBs of the next
15、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-adjustment of dual P-code and carrier phase measurements
16、. 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 observation periods, has relatively better accuracy and effec
17、tiveness 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 precisely determine ionospheric delay with dual-freque
18、ncy 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 ionospheric modelthe Different Area for Different Sta
19、tions (DADS) and its application in China Based 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 investigated which is advantageous for considering t
20、he 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 used 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, and to
