GNSS Monitoring & Evaluation And Early Warning

At present,GNSS is developing rapidly,and the third-generation Beidou navigation satellites are also advancing by leaps and bounds.In 2020,the third-generation Beidou satellite network will be completed and officially put into operation.In this context,it is particularly important to evaluate the comprehensive performance of Beidou satellites.This article analyzes the data quality of Beidou navigation satellites,and comprehensively evaluates and compares the performance of Beidou satellite-borne atomic clocks.At the same time,with the vigorous development of the later satellite operation and maintenance,that is,the monitoring and evaluation center,the demand for GNSS real-time monitoring and early warning is becoming stronger and stronger.Based on this,this article proposes and introduces a GNSS real-time early warning method and the signal-to-noise ratio,The broadcast ephemeris error gave a real-time warning.1.Use MGEX 9 station tracking station data to compare and analyze the data quality of Beidou's third-generation navigation system in terms of integrity rate,multi-path,and signal-to-noise ratio.The results show that the integrity rate of B1 I and B3 I data of BDS-3 is better.Better than BDS-2,B1 C,B2a data integrity rate of BDS-3 is relatively poor;BDS-2satellite pseudorange multipath effect will have a systematic error,this systematic error does not exist in BDS-3;BDS-3 The signal-to-noise ratio of the B2 a frequency point is strong,and there is a non-linear positive correlation between the signal-to-noise ratio and the altitude angle.This correlation can be expressed by polynomial fitting.2.Based on the GNSS receiver comparison test,the domestic monitoring receiver observation data quality evaluation was carried out,and the measurement noise and pseudorange correlation characteristics of the observation data were analyzed.The results show that there are systematic errors in the evaluation of noise by the three-difference method between observation data epochs,and there is autocorrelation in the time series of zero-baseline double-difference pseudorange data.In order to reduce the noise of the pseudo-range measurement data,the pseudo-range data is filtered.3.BDS-3 networking completed,and WUM and WHU precision clock difference products were used to evaluate the BDS-3 full constellation and GPS,Galileo,and GLONASS atomic clocks.The results show that GPS and GLONASS cesium clocks have better accuracy;Galileo and BDS-3 hydrogen clocks have relatively stable drift rates;BDS-3,FOC-mounted hydrogen clocks,and Block-IIF-mounted rubidium have better weather stability.Great.4.In order to realize GNSS real-time warning,this paper proposes a method and process to realize real-time warning,using BNC,RTKLib,and Matlab to give real-time warning to signal-to-noise ratio and broadcast ephemeris.When the signal-to-noise ratio is used for early warning,a model is established by using the relationship between the altitude angle and the signal-to-noise ratio,and the early warning is based on this model;when the broadcast ephemeris is used for early warning,it is realized through the UERE.