A Study Of GPS Single Frequcncy Precise Point Positioning And Regional Ionosphere Model

In recent years, with the accuracy's increase of IGS orbit and clock products,the Un-differenced precise point positioning (PPP) technology have became one of the most extensive technology in GPS application field as its operation efficiency, high precision and low cost advantage.More over, single frequency precise point positioning technology which based on cheaper GPS single rate receivers have received widespread concern.In this paper, a series of theory research and algorithm implementation about single PPP was conducted. A deep research of the ionosphere error which is the most difficult error to deal with for single users was made.Researched the regional ionosphere delay model's establishment and a series of new improvement methods.These research not only provides a new way for the research of the ionosphere activity characteristics, variation rules, and the ionosphere forecasts, but also can effective correct the ionospheric delay for single users and realised nearly the same positioning accuracy for both single PPP and dual PPP in a certain extent.Besides, a new algorithm based on the correction of refference station and is weak equivalent to differenced solution was put forward, and got good location performance in practical applications.In this paper, the research content mainly includes two parts:the first part is single precise point positioning algorithm and model, including the ionosphere parameter estimation PPP model, reference station information corrected PPP model, single rate PPP double frequency solution algorithm and the ambiguity fixed theory about PPP; the second part is the research of ionosphere delay model and variation rules, including the eslablishment of xi'an regional ionosphere model, the analysis of ionospheric delay variation in China area and xi'an regional,also,the ionosphere second order model is established.The main contribution of this study are as follows:(1)Research and analysis various errors and the corresponding corrective action of the single precise point positioning, the influence of antenna phase center correction for PPP positioning is mainly studied,and get a conclution that the antenna phase center offset and variation nearly not affect the horizontal positioning results,but have cm level influence in the elevation direction. The absolutely antenna phase center correct model is better than relative antenna phase center correct model.(2)As the ionospheric delay model correction has low accuracy, poor reliability, the ionosphere delay parameter estimation thoughts was put forward,and establish a new single PPP model while the ionosphere delay use parameter estimation. The feasibility and efficiency of this method was checked throug experiments,and provides new ideas for single users to correct the ionospheric delay.(3)Research and put forward reference station corrected PPP models, this model using the approximate common errors of reference station and user stations, increase the accuracy of the observation values, speed up the PPP convergence speed and improve the positioning accuracy, and have a weak equivalence to difference positioning.(4)Based on the epoch difference ionosphere model, realized the single frequency data inversion to dual frequency data, and realize single rate PPP for double frequency solution. This method greatly shortened positioning convergence time, remarkably raised the single PPP's positioning accuracy, make single rate users get approximate accuracy to dual frequency solution.(5) Analysis problems that the Un-difference observation data ambiguity how to become integer and fixed, put forward PPP ambiguity fixed algorithm based on reference station correction. This ambiguity fixed method can effectively separated the integer part and fractional part of the ambiguity, can significantly shorten convergence time while fixed, and the implementation is simple.(6) Based on phase smoothing pseudorange and least squares fitting method, a regional ionosphere model of xi'an was esttablishment, the variation rules of the ionosphere during summer and winter seasons was reaearched.The establishment of the model,for one thing,provides users with a precision ionosphere products, for another thing, provides important information for space environment monitoring research.(7) Research the extraction method for ionosphere first order and second order delays, establish the quantitative model to analysis the influence of second order delay to point positioning and baseline, and emphatically analysis the variation rules and influence of ionosphere delay to positioning in China region.The ionosphere variation rules of half an year or an year of xian in recent years was studied, get a conclution that he ionosphere second order delay with mm level influence in the elevation direction for positioning. It has an important enlightenment function for deformation monitoring, earthquake hazard prediction, plate motion and other high precision geodesy research and application areas. And with the surface model which contain trigonometric series, established a ionospheric second order delay model, this model can assist correction residual delays of second order delay while use the ionosphere combinationobservation.