Multi-constellation PPP/FCB Ambiguity Resolution And Performance Analysis

As a high-precision absolute positioning technology at global-scale,Precise Point Positioning can achieve centimeter-millimeter level and decimeter-centimeter level highprecision positioning in static and kinematic modes respectively with only one receiver.However,due to the influence of UPD,slow changes of constellation geometry construct,pseudo-range noise,PPP has long convergence time and poor positioning accuracy,which severely restricts its application and development.In recent years,the development of multiconstellation GNSS technology and the achievement of PPP-AR have brought new opportunities for PPP research and application.The multi-constellation GNSS can not only provide more observation information,enhance constellation geometry construct,shorten the initialization time,but also make an important contribution to the accuracy and reliability of the positioning results.Similarly,the PPP-AR can shorten the convergence time and improve the positioning accuracy.In view of this,this thesis focuses on the theory and method of multi-constellation PPPAR to carry out research,and uses the high-precision FCB products to achieve the triconstellation PPP-AR,which significantly enhances PPP performance,and has important reference significance for its further development and even for real-time application.The main work and achievements of the thesis are as follows:1.Based on the precision orbit and clock bias products starting with gbm from GFZ,the influence of three models of Inter-System Bias on positioning performance of the static triconstellation ionosphere-free combination PPP is evaluated.The results indicate that the positioning performance is basically the same when ISB is described as a random walk or white noise process,and it is significantly better than that when ISB is estimated as a time constant.2.The quality of multi-constellation FCB products were evaluated in terms of time stability and the recovery of PPP ambiguity integer characteristics.The results indicate that the WL FCB of the four-constellation remains relatively stable within 47 days,while the NL FCB remains relatively stable within one day.Furthermore,using the observations of 10 MGEX stations to carry out the static tri-constellation PPP-AR experiment.After the correction of SD FCB,the probability distribution of the SD ambiguity residuals was calculated.The results indicate that the proportions of SD WL residuals within ±0.2 cycle for three constellation are 95.1%,98.1% and 76.3%,respectively,while the proportions of SD NL residuals are 96.7%,96.6% and 94.9%,which proves that both WL FCB and NL FCB products have high accuracy and can recover the integer characteristics of PPP ambiguity well.3.Aiming at the problem that the failure for FAR caused by un-convergence ambiguities,this thesis uses high-precision FCB products to achieve PAR for GPS PPP,and control the influence of un-convergence ambiguities effectively.Then,15-day observations from 51 MGEX stations were used to compare and analyze the positioning performance of PAR and FAR.The results indicate that,compared with FAR,the TTFF of PAR is shortened by 15.2min and 19.9min,and the fixing rate is increased by 27.8 and 30.8 percentage points respectively in static and pseudo-kinematic modes.4.In view of the problem that long convergence time and poor positioning accuracy in PPP ambiguity resolution of single constellation,the tri-constellation PPP-AR was achieved by using the PAR strategy based on the high-precision FCB products.Then the 10-day observations from 21 MGEX stations were used to compare and analyze the PPP positioning performance of different constellation combinations.The results indicate that the fusion of triconstellation can significantly improve PPP positioning performance: The static triconstellation PPP takes only 9.5min to achieve the first fixing(6.7 min shorter than single GPS),and the fixing rate reaches 99.49%.When the observation time is 0.5h,the positioning accuracy of fixed solution in E,N,and U components is 0.6cm,0.6cm,and 2.2cm,respectively,which are 88%,60%,and 51% higher than that of float solution.In the pseudo-kinematic mode,the tri-constellation PPP takes only 10.7min to achieve the first fixing(11.1 min shorter than single GPS),the fixing rate reaches 98.5%.Meanwhile,the positioning accuracy of triconstellation PPP-AR is 53%,24% and 21% higher than that of the float solution in the components of E,N and U,respectively.