For dual-frequency single-point positioning(SPP)with the BeiDou navigation satellite system(BDS),the B1I and B3I frequency combination is typically used.In order to fully investi-gate the positioning potential of the BDS-3 system,the performance of SPP is investigated using various dual-frequency pseudorange combinations of different BDS-3 frequencies.The differential code bias(DCB)correction formula is derived,and a mathematical model for SPP positioning using any dual-frequency combination of BDS-3 is established.Using 121 days of actual data from 35 global MGEX tracking stations and an improved RTKLIB software,SPP solutions with ionosphere-free dual-frequency combinations of BDS-3 are computed globally.First,a comprehensive evaluation of the quality of six BDS-3 frequency signals is performed,including signal-to-noise ratio,multipath effects,and data availability.Then,the performance of fourteen BDS-3 dual-frequency pseudorange com-binations is compared after applying DCB corrections.The study shows that the B2ab signal has the highest quality in terms of multipath error,signal-to-noise ratio,and data integrity,followed by B2b and B2a,then B3I and BIC,with B1I performing relatively poorly.Of the fourteen differ-ent dual-frequency combinations for BDS-3 SPP,the positioning accuracy after DCB correction is significantly better than that without DCB correction.Compared to the uncorrected case with a three-dimensional accuracy of 14.9 m to 31.2 m,the DCB correction improves the accuracy to 1.7 m to 15.5 m.Influenced by the noise enhencement factor of the ionosphere-free dual-frequency combination model,the optimal combination is B1C&B2a with an accuracy of 1.7 m,while the worst combination is B2a&B2ab with an accuracy of 15.5 m.These results provide a valuable reference for the implementation of BDS-3 pseudorange positioning in various fields,in-cluding vehicle navigation.
BDS-3Pseudorange single-point positioningFrequency signal qualitySatellite dif-ferential code biasDual-frequency pseudorange combination
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