Research On BDS/GNSS Signal-in-Space User Range Evaluation Method

The positioning accuracy of satellite navigation systems depends on a variety of influence factors.Generally,in the performance analysis,it is agreed to separate the geometry-related factors from the measurement and modeling errors which is known as user equivalent range error.The user equivalent range error includes signal-in-space user range error,ionosphere,troposphere,receiver noise and multipath.The signal-in-space user range error describes the statistical uncertainty caused by space segment broadcast orbit and broadcast satellite clock error,which is one of the main error sources for reducing the accuracy and integrity of positioning and reflects the comprehensive influence of the orbit error and clock error contained in the broadcast ephemeris on the user's ranging under certain data age conditions.With the continuous development of global positioning system,performance evaluation can provide reference for navigation and positioning users and the next step of system construction.Therefore,it is of great theoretical and practical significance to study the key technology of GNSS spatial signal accuracy evaluation.In this paper,the key technology of BDS/GNSS signal-in-space user range error evaluation is studied.The theory and method of signal-in-space user range error evaluation are introduced systematically,and the BDS/GNSS signal-in-space user range error evaluation software is designed and developed independently.On this basis,by analyzing the data of broadcast orbit and broadcast clock error from 2016 to 2018,the statistical results are given on a monthly basis,and then the correlation between the broadcast orbit and the broadcast clock error is analyzed.Signal-in-space user range error under different correlations is verified.The main research work and contributions of this paper are as follows:1.Summary of the research status of GPS/BDS/GALILEO/GLONASS navigation satellite system performance evaluation at home and abroad.The study found that when the BDS signal-in-space user range accuracy is evaluated with reference to different precise products,the results will have large differences.When analyzing the reasons,it is found that the antenna phase center correction models adopted by the BDS organizations are different.The use of different PCO/PCV models leads to the inability of the original evaluation method.Therefore,we need to improve the original evaluation method.2.The influence of different PCO models on BDS precise orbit and precise clock difference is investigated by the measured data.The results show that the influence of different PCO on the precise orbit is only centimeter,and the influence on the cross direction and the along direction is greater than the radial direction.Most of the difference in the z component of different PCO models of the same satellite will be absorbed by the precise clock difference,and the residual amount is less than 1dm.On this basis,the accuracy evaluation method of BDS signal-in-space user range error considering different antenna phase center correction models is proposed.Moreover,the BDS/GNSS broadcast orbit and broadcast clock are inconsistent with the precise orbit and the precise clock reference point.Therefore,the accuracy evaluation method that takes into account the different antenna phase center correction models is applicable to the BDS/GNSS broadcast ephemeris signal-in-space user range error evaluation.3.Through the broadcast orbit data of 2016-2018,the PCO of the BDS/GNSS broadcast orbit antenna is demonstrated and evaluated.The PCO of the single satellite broadcast ephemeris antenna is given for the first time.In particular,through long-term data verification,we found that BDS broadcast orbit error characteristics have changed.Many satellites have been adjusted in mid-January 2017.Some satellites have been adjusted at other times,and their antenna phase center offset has a certain degree of volatility.The phase center offset of the GPS/GALILEO/GLONASS broadcast ephemeris antenna is relatively stable over a long time scale.4.The correlation between the BDS broadcast orbit and clock is further studied.The negative correlation is obtained.On this basis,the evaluation method of the BDS signas-in-space user range error is improved.5.Based on the data of 2016-2018,the GPS/BDS/GALILEO/GLONASS signal-in-space user range error evaluation work is carried out.GPS URE is 0.2m-0.5m.BDS GEO URE is between 0.5m and 1.0m,and BDS MEO/IGSO is between 0.3m and 0.65 m.GALILEO is under 0.15 m.