Analysis And Research Of GNSS Positioning Performance Based On QZSS

In recent years,QZSS,a regional satellite navigation system developed by Japan,has developed rapidly.It provides both GPS-compatible traditional PNT services as well as related augmentation services and information services.It covers the eastern part of China and the South China Sea,which can be used as a supplement to the Beidou System in China,and is very necessary for the rational use of the QZSS system in China.At present,researches on QZSS are mostly focused on the combination of QZSS and a few GNSS single point positioning.In order to comprehensively evaluate the influence of PNT service and augmentation service of QZSS on GNSS positioning performance,the main research contents and results of this paper are as follows:(1)The basic situation and development history of QZSS system are systematically sorted out.The orbit,type,coordinate system characteristics,signal type and service of QZSS are introduced in detail.The calculation algorithm of QZSS ionospheric delay and the way to confirm its running state are described.The combination of SSR information broadcast by QZSS and broadcast ephemeris is used to carry out PPP experiment,and the RMS value of positioning error and the convergence time are analyzed.The results show that in the static PPP mode,the positioning error RMS values in X,Y and Z directions are in the range of 1.0?1.6cm,and the convergence time is in the range of 12?49min.In the kinematic PPP mode,the positioning error RMS values in X,Y and Z directions ranged from 3.5 to 5.2cm,and the convergence time ranged from 47 to 111 min.(2)At present,there are few studies on the positioning performance of MADOCA precise products.In order to reasonably select the subsequent experimental data,SPP and PPP comparative experiments were carried out on the positioning performance of MADOCA products and MGEX products.The SPP experiment results show that,compared with MADOCA data,the average number of available satellites is 4 ? 10 more when using MGEX data,the average success rate of solution is increased by 4%? 5%,and the positioning accuracy is increased by about 1 times when using MGEX data.However,the PDOP value when using MGEX and MADOCA data has little difference.PPP experiment results show that,when the elevation mask is 15°,compared with MADOCA product,the 3D positioning accuracy is improved from 9.86 cm to4.86 cm,which is about 5.00 cm,and the convergence time is improved from 32.63 min to 11.13 min,which is about 20.00 min.For kinematic PPP mode,compared with MADOCA,the 3D positioning accuracy is improved from 27.50 cm to 8.74 cm by MGEX,the positioning accuracy is improved by about 20.00 cm,and the convergence time is improved from 120.00 min to 11.75 min,which is about 110.00 min.Overall,the current positioning performance using MGEX products is better than the positioning performance using MADOCA products.(3)This paper analyzes the impact of QZSS on GNSS SPP in the Asia-Pacific region,and carries out comparative experimental processing on the positionable epochs and positioning accuracy results of single GPS/BDS/Galileo SPP and QZSS+GPS/BDS/Galileo combined system SPP.The results show that QZSS improves the available epochs of GPS/BDS/Galileo SPP to different degrees,and the improvement of Galileo is the largest,GPS is the second,and BDS is the least.The influence of QZSS on the positioning accuracy of GPS/BDS/Galileo SPP is quite different.The improvement range of BDS positioning accuracy is in decimeter level,and the improvement range of GPS positioning accuracy is in decimeter to meter level.QZSS makes the positioning accuracy of Galileo decrease,and with the increase of elevation mask,it reduces the positioning accuracy of Galileo system SPP more seriously.(4)This paper analyzes the impact of QZSS on GNSS PPP in the Asia-Pacific region,and conducts static and kinematic PPP experiments on single GPS/BDS/Galileo and QZSS+GPS/BDS/Galileo combined systems.The results show that QZSS can improve the PDOP values of different system positioning,and the improvement effect is positively correlated with the elevation mask.The effect of convergence time on positioning of different systems is different,so that the positioning convergence time of BDS is basically shortened in the two modes.The convergence time of the two GPS positioning modes is basically unchanged at 7° and 15°,while the overall convergence time is reduced at 30°.The convergence time of Galileo's two positioning modes is basically unchanged at 7° and 15°,and decreases in E and N directions at 25° and 30°,In U direction,the convergence time of static PPP is shortened,and the convergence time of kinematic PPP is prolonged.The proportion of positionable epochs of different systems has been improved,and the improvement of Galileo system is the largest.They are different effects on positioning errors RMS values of different systems.The RMS is increased in the U direction,the RMS of the positioning errors of BDS decreases slightly in the E and N directions,while the RMS of the positioning errors of GPS and Galileo increases slightly.Because this article RMS value is based on the direction error converge to less than 10 cm of epoch.Compared to the single GPS/BDS/ Galileo system,the positionable epochs accounted of QZSS + BDS/GPS/Galileo system are more than the former,and the differences of both are enlarged with the increase of elevation mask.thus epochs to calculate RMS of the latter is greater than the former,the result reflects the differences between QZSS and different navigation systems.There are 67 pictures,30 tables and 115 references in this paper.