Algorithm Research And Performance Analysis Of GNSS Precise Point Positioning

Global Navigation Satellite Systems is booming.In the past,the single-system positioning era is gradually changing into an era of multi-system combination,and multi-system combination PPP has become an inevitable trend.At present,the research on multi-system PPP function model is becoming more and more mature.However,in the face of the complexity of signal propagation,the diversity of error sources,and the differences in the quality of precision products,how to accurately determine the random model and obtain high-precision precision products is an urgent problem for multi-system PPP.In response to the above problems,the main research content and results of this article are as follows:(1)First,the basic theory of GNSS precise single-point positioning is introduced.Including the conversion of different systems,coordinates and time;then introduced the precise single-point positioning model without ionospheric combination,Uof C,and non-differential non-combination.Based on a single system,a multi-system precision single-point positioning model that takes into account the deviation between systems is derived.;Next,several error sources in PPP are introduced and the corresponding correction models and weakening methods are given.Finally,the least square parameter estimation method is introduced.(2)Then a GNSS combined weight model is proposed for multi-system combined positioning.Among them,firstly,the variance of different systems is determined according to the Helmert variance component;then each satellite is weighted according to the optimal altitude angle model verified in this paper;finally,the combined weight model proposed in this paper is applied to PPP,and the results show : Compared with the equal weight model,the positioning accuracy of the combined weight model can be improved by about 10% both statically and dynamically.(3)Next,the GNSS clock error products in the Australian region were quickly obtained through fewer stations in a fixed area.Among them,firstly,by fixing three stations in Australia,the satellite clock error is estimated while estimating the position parameters of the rover;then the clock error result is made the second difference with the WUM clock error product provided by Wuhan University,including GPS,BDS,The clock errors estimated by the GLOANS system are all better than 0.06 ns,which are in good compliance with the WUM clock error products.Finally,the estimated clock error is applied to the PPP of different systems,and its positioning accuracy also has good compliance.(4)Based on the weight model of the combined system proposed in this paper,apply the estimated clock error product to the precise single-point positioning of different single-system and multi-system combinations,and discuss the GEO/IGSO/MEO satellite-to-single system and the single system in different orbits.The impact of the combined system.Among them,adding different BDS satellite constellation structures can improve the positioning accuracy of the static single system BDS by more than 40%,and the dynamic can reach 60%.For multi-systems,the improvement accuracy is below 10% statically and 20% dynamically.The paper has 42 pictures,17 tables,and 84 references.