Tropospheric Modeling And Delay Errer Analysis Based On The GNSS Signals

With the progress and development of GNSS (Global Navigation Satellite System) technology, the application scopes of GNSS have been more and more widespread, especially in the fields of positioning and atmospheric measurements. However, while it passes through the troposphere, due to the asymmetrical distribution of atmosphere, GNSS signal will be inevitably delayed. Regardless that it serves as an error in the field of precise positioning, or that it serves as a data resource in the field of GNSS Meteorology, the tropospheric delay error is required to be researched and analyzed. This dissertation researched on correction of tropospheric delay error by the theory of modeling.This dissertation first analyzed the tropospheric climatic characteristics and electromagnetic properties, and then established the relationship between refractive index and meteorological parameters such as atmospheric temperature, pressure and vapor pressure in the form of function. Thereby, it deeply analyzed the causes and results of the tropospheric delay error, and then obtained the expression of function that was used to compute the tropospheric delay error using meteorological parameters. After that, it focused on the curved-path delay which can lead to delay error. By analyzing and discussing, it obtained the relationship between curved-path delay could be neglected if the satellite elevation angle was above 15o.As is known, modeling method can be divided into two parts: the module of zenith delay and the module of mapping function, which can be studied respectively. Mastering the theories of classical zenith delay models and classical mapping function models, this dissertation analyzed the influence factors which can cause errors of classical zenith delay models, and then ascertained the degree affected by the location of observation station and meteorological parameters temperature, pressure and vapor pressure for Saastamoinen, Hopfield and EGNOS model. By comparison of the three classical models, it shows that under standard atmospheric conditions, EGNOS model got minimal impact by meteorological parameters, and Saastamoinen model was affected greatest by the elevation of observation station, but Hopfield model was affected least by the elevation of observation station.Besed on the theory of refractive index modeling, and according to the analysis of meteorological data in Harbin district, this dissertation respectively completed data fit to tropospheric zenith delay of four seasons, and then built a tropospheric zenith delay model which is suitable in Harbin. Subsequently, the dissertation compared Harbin Model with Saastamoinen, Hopfield and EGNOS model, thereupon demonstrating that Harbin Model is more suitable for describing the tropospheric condition in Harbin, and comparing with classical zenith delay models, Harbin Model can get a more precise error correction in Harbin.