| Precise Point Positioning(PPP)breaks through the distance limitation and reduces the cost of positioning,Compared with the original differential positioning.It has been widely used in the fields of navigation,deformation monitoring,meteorology,and autonomous driving.However,in the traditional PPP solution process,the ambiguity absorbs Uncalibrated Phase Delays(UPD).Therefore,the traditional PPP solution method can only obtain the floating ambiguity.In order to obtain an integer Ambiguity Resolution(AR),UPD correction products broadcast by various analysis centers of the global satellite navigation system service organization are generally used to correct floating-ambiguity.However,the UPD correction products of various analysis centers currently have low support for BeiDou Navigation Satellite System(BDS),especially BDS-3 satellites.Therefore,the realization of BDS-3 PPP-AR based on BDS-3 UPD products estimated is of great significance for expanding the application of BDS-3 in various high-precision positioning fields.Focusing on this core goal,this article focuses on data quality analysis and control,BDS-3 UPD estimation and BDS-3 PPP-AR.Specific research content and results include:(1)In terms of data quality analysis and control,the research is mainly carried out from three aspects:the analysis of precision products and broadcast ephemeris quality,and the construction of the pseudo-range deviation correction model.First,the quality of the precise products is analyzed in terms of conformity between products and support for BDS-3 satellites.It was found that the data from the two analysis centers of Wuhan University(WUM)and the German Research Centre for Geosciences are most suitable for BDS-3-related experiments.Then,the BDS-3 broadcast ephemeris was analyzed,and it was found that the accuracy of the orbit and clock difference of BDS-3 was significantly improved compared to BDS-2.For the BDS-3 satellite broadcast ephemeris,the accuracy of the Medium Earth Orbit(MEO)satellite is 0.276 m,and the accuracy of the Geostationary Earth Orbit(GEO)satellite is the worst at 0.571 m.Finally,in view of the pseudo-range deviation of the inclined earth orbit(IGSO)and MEO satellite observation data,a single-satellite correction model related to the elevation angle is constructed.At the same time,a time-dependent correction model was constructed for GEO satellites.The results using the correction model show that the standard deviation of IGSO/MEO pseudo-range deviation series can effectively reduce by 6.3%-40.7%,and GEO can effectively reduce 0.4%-53.6%.In reducing the standard deviation of the wide lane(WL)combined series,all satellites can be reduced by 21.0%-39.6%.(2)Regarding the autonomous estimation of BDS-3 UPD,a non-difference and ionospheric combined model was derived in detail and it was verified by the measured data of 313 stations.At the same time,from the aspects of product stability and reliability,the quality of self-estimated products and their spatial influence factors are analyzed.The results show that it is feasible to estimate the BDS-3 UPD product using the undifferenced and ionospheric-free algorithm.In terms of stability of self-estimated UPD products,the fluctuation range of WL UPD within a month is less than 0.01 cycle,and that of Narrow Lane(NL)UPD products is less than 0.3 cycle.At the same time,when the number of available measuring stations is higher than 40,the fluctuation range of NL UPD products will be reduced to less than 0.2 cycle.Among them,96%of the satellite are less than 0.2 cycle for NL UPD fluctuations within a single day,and 42%are less than 0.1 cycle.In terms of reliability,the 94.4%of WL UPD residuals during a day are within ±0.15 cycle,and 99.1%are within ±0.25 cycle.Compared with the WL UPD,NL UPD is poor in terms of reliability.Its residual error is only 82.6%within ±0.15 cycle,and 99.8%within ±0.25 cycle.Secondly,this article found through experiments that increasing the number of stations will help improve the stability and reliability of UPD products,and the closer station to the satellite sub-satellite track,the higher the fixing percentage.(3)Regarding BDS-3 PPP-AR,a fixed inter-satellite single-difference ionospheric free ambiguity model was derived in detail,and static positioning experiments were carried out using observation data from 16 global observatories.At the same time,the positioning accuracy of single BDS PPP-AR based on self-estimated UPD products and WUM UPD products is compared and analyzed,convergence time and fixing percentage.The results show that single BDS ambiguity can be fixed by using self-estimated UPD products,and it is higher than the fixed percentage using WUM UPD products.At the same time,based on the self-estimated UPD product,the positioning accuracy of the single BDS PPP-AR in the three directions of east,north,and zenith is 0.88,0.76,and 1.57 cm,respectively,which is 33.9%,23.2%,and 40.3%higher than the floating-point solution.Secondly,after the introduction of the BDS system,the positioning accuracy and convergence time of the multi-system combination PPP-AR can be significantly improved.In terms of the accuracy of the static 3D fixed solution,the combination of Global Positioning System(GPS)and BDS is 0.92 cm,which is better than the 0.96 cm of the combination of GPS and Galileo.At the same time,compared with single GPS,these two combinations have improved 3D positioning accuracy by 24.0%and 22.3%,respectively.In terms of convergence time,the combination of GPS,BDS and Galileo takes 12.5 min,which is a 7.4%reduction compared to the 13.5 min of the GPS and Galileo combination.Figure[38]Table[10]Reference[103]... |
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