Research And Implementation Of GNSS Navigation Data Monitoring Method

With the development and application of Global Navigation Satellite System(GNSS),the performance of PVT(Position,Velocity and Time)services of GNSS systems has been increasingly concerned by users and systems.The real-time monitoring and post-assessment of navigation messages is one of the important means for assessment the performance of system,and it can also provide important empirical informations for improving the service performance of the system.Now,most of the theoretical researches on monitoring and assessment algorithms are focused on assessment,few researches on monitoring.And many scholars confuse monitoring and assessment definition,so they can't understand essentially and actualize real-time monitoring of navigation messages.The research on GNSS navigation message monitoring algorithm has a great significance.The data come from GNSS real-time navigation messages and ultra-fast precision products,and the accuracy,correctness and rationality of navigation message parameters is three important part for the researches on navigation messages monitoring algorithm.This paper did experimental verification and analysis for each algorithm,implemented the GNSS navigation message monitoring software in the end.The main research contents of the paper are as follows:1).The definition and object of GNSS navigation message monitoring and evaluation were ascertained.Detailed analysis the navigation message parameters of GPS and BDS.Established a perfet norm of navigation message monitoring.According to the characteristics of the parameters,the monitoring parameters are divided into three categories: accuracy monitoring parameters,correctness monitoring parameters and rational monitoring parameters.The monitoring methods corresponding to the three types of monitoring parameters are proposed.2).Detailed description of the accuracy monitoring method and proposed an adaptive threshold calculation model.The model uses the parameter error value distribution model to calculate an accurate and reasonable threshold.The error distribution model based on the long-term evolution characteristics of navigation message parameters.In this paper,the multi-system navigation messages provided by IGS for nearly two consecutive years and precision products were used to study the errors of broadcast ephemetical orbit errors,satellite clock errors,and broadcast ionospheric delays.Hypothesis testing of the error distribution model,then establish the error distribution model,Correctly calculate the monitoring threshold of each precision monitoring parameter in the end,which has a great significance for GNSS monitoring work.3).Detailed description of the monitoring algorithm for correctness and rationality monitoring of each parameter,where the correctness parameter emphasizes its uniqueness and the rationality parameter is within a tolerable range.Two methods of consistency check and continuity test are proposed in the correctness monitoring,the original frame structure data flow received by Ublox is used for real-time monitoring,verification and analysis.In the method of rationality monitoring,a joint method that combines the evolution characteristics of GPS and BDS parameters for nearly two consecutive years and the provisions of ICD documents is proposed which used for determine a correctly tolerable range of rationality monitoring parameters.4).Based on the mainstream development technology of GUI software,the overall structure design and detailed design of functional modules of GNSS navigation message monitoring software were established.The software implemented the function of real-time monitoring,which including four functions: accuracy monitoring function,correctness monitoring function,rationality monitoring function and the monitoring threshold analysis function.