Abstract
Global navigation satellite system real-time kinematic (RTK) normally takes advantage of a common-frequency (CF) model, in which, the frequency bands in use are assumed to be the same across all satellites visible to two receivers. This assumption discards satellites whose frequency bands differ from the majority of satellites, thereby weakening the CF model. In this contribution, we present a mixed-frequency (MF) RTK model that considers all satellites whose frequency bands may vary from each other. Due to the new rank deficiencies in the MF RTK model, the formulation of the MF RTK model needs to choose a set of unknown parameters as an S-basis based on the S-system theory. The formulated MF model is more generally applicable than the CF model, particularly for the BeiDou navigation satellite system (BDS) since its second-generation (BDS2) satellites broadcast B1I, B2I, and B3I signals and its third-generation (BDS3) satellites broadcast B1I, B3I, B1C, B2a, and B2b signals. To verify, we collected BDS data at a static station and a kinematic vehicle which are a zero-baseline and an approximate 10 km baseline, respectively, to test the MF model and compared it with three CF models employing BDS2 B1I + B2I + B3I (CF1), BDS3 B1I + B3I + B1C + B2a + B2b (CF2) and BDS B1I + B3I (CF3) observables. Both static and kinematic results show that the MF model outperforms the three CF models regarding the time-to-first-fix of integer ambiguity resolution and positioning accuracy. The MF model obtains the most accurate positioning; the fixed positioning errors (95% quantile) in the east, north, and up components are, in cm, 0.094, 0.081, and 0.230 in the static test and 5.49, 6.30, and 9.54 in the kinematic test, respectively. Compared with the CF model utilizing all BDS satellites (CF3), the MF model reduces the positioning error by 21.7%, 19.0%, and 11.5% in the east, north, and up components in the static test and 52.7%, 57.6%, and 58.4% in the kinematic test, respectively.
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The data used to support the findings of this study are available from the corresponding author upon request.
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Acknowledgements
This work was funded by the National Natural Science Foundation of China (Grant No. 42022025). The corresponding author is supported by the CAS Pioneer Hundred Talents Program.
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CK processed the data and analyzed the results. CK and PH wrote the manuscript. BZ proposed the method, designed the research, and wrote the manuscript.
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Ke, C., Hou, P. & Zhang, B. GNSS-RTK model: common-frequency versus mixed-frequency. GPS Solut 27, 128 (2023). https://doi.org/10.1007/s10291-023-01465-x
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DOI: https://doi.org/10.1007/s10291-023-01465-x