Analysis Of The Influence Of Different Mapping Functions On Real-time PPP Solution

Now,the delay of troposphere is one of the main factors affecting real-time PPP highprecision solution,which will not only affect real-time PPP convergence speed,but also reduce positioning accuracy.Therefore,some measures must be taken to eliminate or reduce the influence of tropospheric delay.At the same time,the surface meteorological model,zenith tropospheric dry delay correction model,mapping function and parameter estimation method and other factors affect the correction accuracy of tropospheric delay.Therefore,this paper mainly discusses and analyzes the above four aspects,and the research contents and conclusions are as follows:1.The principle of precise point positioning and the basic observation equation are discussed in detail.The causes,characteristics and correction methods of various GNSS errors are systematically described.The detailed formula is given to project the errors to the propagation direction,and the unit is m.2.Based on the radiosonde data in 2019,the accuracy of the ground meteorological model and the zenith tropospheric dry delay correction model are analyzed respectively.The results show that the GPT has the best accuracy only near the equator(0 ° to 5 °),GPT2?GPT2w and GPT3 have little difference.No matter which weather model is used,the dry delay correction accuracy of the Saastamoinen model is better than that of the Hopfield model.3.The formulas of recursive least square and extended Kalman filter,which can be used for real-time PPP parameter estimation,are derived.In view of the shortcomings of extended Kalman filter,a new Kalman filter,adaptive robust Kalman filter,is introduced.The results show that the adaptive robust Kalman filter can not only improve the positioning accuracy,but also effectively weaken the influence of abnormal observation value.4.The influence of mapping function selection on real-time PPP solution under different satellite system combinations is compared and analyzed.Experiments results show that the accuracy and convergence time of multi system combination are better than that of single system GPS;the choice of mapping function has little influence on the plane accuracy and convergence time,but has great influence on the U direction;VMF3 has the best positioning performance,GMF and VMF1 have little difference,but they are better than NMF.