A Study Of The Theory To Real-time GPS Sensing Of Water Vapor Technology

Usually the method to get water vapor makes use of the pattern of relative positioning, and the pattern of single point positioning has many virtues comparing with the pattern of relative positioning. The paper was based on this idea, then the pattern of un-differenced precise point positioning and IGS Ultra rapid product are used to do the research of real time GPS sensing of water vapor. The main works and contributions are as follows.1. To un-differenced precise point positioning, the influence of diversified error sources should be accurately considered. All kinds of error sources are detailedly analyzed and discussed, and the errors including ionospheric delay, clock error, relativistic correction are summarily estimated, their influencing degree is analyzed in the data.2. Three kinds of models of carrier phase observation value linear combination are deduced such as wide lane, narrow lane and free ionosphere. The three linear combinations are analyzed and their uses are discussed.3. Aiming to the trait of un-differenced precise point positioning, wide lane method and ionosphere residual error method are detailedly deduced, many times difference method and wide lane method and ionosphere residual error method are synthetically utilized to detect and repair the cycle slip.4. The whole process that double P code method is used to make certain the ambiguities is full detailedly deduced, the time to fix the narrow lane ambiguity is longer than the time to fix the wide lane ambiguity, there is a problem to which needs to be paid attention.5. Familiar model of zenith hydrostatic delay are Hopfield model and Saastamoinen model, usually the latter is chosen. Six kinds of mapping function is showed and rationally chosen according to the need. Three estimate methods of zenith wet delay parameters are compared, stochastic process method is more perfect estimate method of tropospheric delay.6. The dual-frequency carrier phase observation equation is built and ionosphere-free predigested, the estimate formula of zenith wet delay is deduced with least square method. After the examples are analyzed, there are problems which need to be solved such as ambiguity, real-time clock bias error and the estimate method of zenith wet delay.7. Mean temperature of the atmosphere is the key to affect the precision that zenith wet delay is converted to water vapor, after four methods to get it are compared, for synthetical thought, the model advised by Mao jie-tai etc is used. The detailed error analysis is done to the ground-based GPS sensing of water vapor content, zenith wet delay is primary error source.