Accuracy Assessment And Analysis Of GNSS Signal In Space

At present,GNSS is developing rapidly.BDS,GPS,GLONASS and Galileo,the four major satellite navigation systems in the world,are continuously developing and improving.QZSS,NAVIC and other regional satellite navigation systems are also following.On the one hand,all countries are accelerating the completion of the system construction.On the other hand,in order to provide a higher service performance of satellite navigation system,the monitoring and assessment of performance and optimization work are also carried out at the same time.There is no doubt that achieving the excellent performance of satellite navigation system in various fields has become the common goal of all satellite navigation systems.Aiming at the important part of GNSS signal in space accuracy,this paper assesses and analyzes the broadcast ephemeris accuracy,broadcast ionospheric delay model correction accuracy and satellite clock performance of BDS,GPS,GLONASS and Galileo satellite navigation systems.The main research work and conclusions are as follows:1.The knowledge of time and coordinate system related to satellite navigation is introduced in detail,and points out the importance of time and coordinate framework as well as the impact on GNSS interoperability.The time and coordinate frame of GNSS is of great significance to monitoring and assessment,which is related to the accuracy of assessment.2.The system assesses the accuracy of BDS,GPS,GLONASS and Galileo broadcast ephemeris,including broadcast orbit,broadcast clock difference,SISRE and TGD.The results show that the accuracy of SISRE of BDS-3 satellite is higher than that of BDS-2,Galileo has the highest accuracy,BDS-3 is equivalent to GPS,and GLONASS has the lowest overall accuracy.3.BDSK8,BDGIM,GPSK8 and Ne Quick broadcast ionospheric delay correction models are introduced,and the accuracy of GNSS ionospheric model correction is evaluated by using the ionospheric parameters of GNSS message and the post code global ionospheric grid data.The results show that in the global region,BDGIM correction accuracy is the highest,performance of Ne Quick in mid latitude and high latitude is better than GPSK8;in China and surrounding areas,BDGIM and BDSK8 correction accuracy in daytime is higher,GPSK8 and Nequick are second;Nequick model correction accuracy in all latitudes is the same,BDGIM and GPSK8 correction accuracy in northern hemisphere is better than that in southern hemisphere,and the correction effect in low latitude area is better than that in high latitude area.4.The performance of the atomic clock of BDS,GPS,GLONASS and Galileo is assessed.The evaluation results show that BDS-3 hydrogen clock,GPS Block-IIF rubidium clock and Galileo FOC hydrogen clock have high stability,with a daily stability of 10^-15magnitude;cesium clock and hydrogen clock have better frequency accuracy and drift rate than other types of clock.