Research And Application Of Real-time GNSS Regional Troposphere Modeling

With the flourishing development of GNSS,it has been widely used in various scopes,such as Geodesy and Geodynamics,meteorological forecasting,marine surveying,engineering surveying and environmental monitoring.Due to the influence of tropospheric refraction during the satellite signal transmit in the troposphere of the earth,it may cause speed delay,inflect delay and the bending of the propagation path.At the same time,the demand for real-time high-precision Precise Point Positioning(PPP)is increasing.Tropospheric delay is the main errors of improving the precision of GNSS positioning and convergence time.This problem has attracted extensive attention of many scholars in the world.The dry delay and the wet delay are usually corrected by the empirical model and the parameter estimation separately in PPP.Because of the strong correlation between the tropospheric delay and the station elevation,the convergence time of PPP is longer and the accuracy of elevation direction is difficult to improve.Simultaneously,the regionality of tropospheric delays is obviously,which lead empirical models cause larger model errors when applied to small areas.In order to overcome the above problems,the real-time regional zenith tropospheric delay correction model is established.The model is based on the measured data of the regional CORS network reference station,which constructed for the tropospheric dry and wet components respectively.The paper introduces the following work:(1)Through the analysis of the reason of tropospheric delay errors,it introduce some common empirical tropospheric model and give a simple description of these models.At the same time,summary of relevant theories and methods of regional zenith tropospheric delay model,which can provide guidance for building regional real-time tropospheric delay model.(2)A real-time regional tropospheric correction model is proposed,which use the weighted inverse distance OFCs model and weighted inverse distance plane fitting model to modeling dry component and wet component of the tropospheric delay respectively.It overcomes the influence of the meteorological parameter error.At the same time,it can obtain the high precision regional zenith tropospheric delay result without the meteorological parameters.The model value can be used as prior constraint of the tropospheric parameters in the PPP,which can improve the PPP convergence time and the location precision.(3)Using the observation data of Guangdong and Xinjiang regional CORS network to get zenith tropospheric delay to construct the real-time regional tropospheric correction model.The model is compared with the commonly used parameter estimation methods and OFCs model.In Xinjiang and Guangdong,the model has the equivalent tropospheric delay correction accuracy.And the model has higher accuracy than the parameter estimation method and the OFCs model,which improved about 1cm and 2cm respectiely.(4)ZTD calculated from the regional zenith troposphere delay model is applied to the real-time dynamic PPP solution,which can get higher accuracy and shorter convergence time than parameter estimation.The comprehensive positioning results of of Xinjiang and Guangdong shows thet the averaged accuracy improvement on the east,north and up component is 40%.Meanwhile the speed of convergence is increased,and the convergence time is shortened by about 10 minutes.