| In order to improve their capability, the upcoming Global Navigation Satellite System(GNSS)will be equipped with multi-carrier frequencies in the future. To give a technique support of the application on the multi-frequency data in high precision positioning, this paper makes a study on the processing and application of multi-frequency GPS data,Detailed researches were done about absolute positioning, relative positioning, ionosphere-modeling and ambiguity resolution by using multi-frequency data. The main works are as the following:1) To solve the problem of multi-frequency data-acquiring, the data simulation methods were discussed in detail. By reconstructing the GPSSIM module in the Bernese software, the data in multi-frequency were acquired, which were approved to be coincident with the reality of the surveying and can be used in many surveying.2) On the basis of the general expression of phase combination, considering the effect of wavelength, noise and ionosphere error, the coefficient selection method were presented on the combination of GPS multi-frequency surveying. At the same time, made a characteristic analysis and a compare of the combination of L3,L5C and L1, according to the precise point positioning. Then, according to an example of relative positioning, illuminated the function of the linear combination in the steps of resolution with the Bernese software.3) Deduced the combined expression in detail, which eliminated the ionosphere correction in the second-order term. Based on International Geomagnetic Reference Field (IGRF) 2005 and the Center of Orbit Determination in Europe (CODE), made an error analysis for ignoring of the second-order term in double ionosphere correction in different latitude. It shows that where there has a lot of electrons, the correction can arrive to 2cm, so it must be considered in precise positioning. Determined the single point position in precise by using simulative tri-frequency surveying data, and compared the effects on precise single-point positioning with dual-frequency combination for eliminating ionosphere influence on different noises.4) Based on the ionosphere modeling precision analysis of different frequency combination, validated in experiment for the first time that when using L1/L5 instead of L1/L2, it can improve the modeling precision in 0.1TECU. Using the simulated multi-frequency data of 200 tracing station, through the Spherical Harmonics of level 15 and order 15, acquired the model with the ionosphere error pseudo-range combination of L1/L1, L2/L5 and L1/L5 respectively. The result shows that L1/L5 can improve the modeling precision efficiently while L2/L5 can't be used to ionosphere modeling.5) Made an introduction in detail on some kinds of method in determining the integer ambiguity, including QIF and LAMBDA. With the practically surveying data, validated the methods of QIF and MW in their reliability and applicability for different baseline. As for the tri-frequency ambiguity decomposing method of CIR, analyzed the influence of ionosphere and noise on every steps of it in theory, and discussed the effect on success rate.6) Evaluated the different factor influence on ambiguity precision, and analyzed the influence on resolution success rate of the multi-frequency data with different baselines, using the ambiguity dilution of precision (ADOP). It proves that on condition of adding multi-frequency data, the success rate of determine wouldn't be improved obviously for short baseline but would be for long baseline with 30 percent. |
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