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<p>All GLONASS-M+/K1B/K2 satellites are capable of transmitting legacy L1 and L2 signals based on frequency division multiple access (FDMA) modulation and new L3 signal based on code division multiple access (CDMA) modulation. The new-generation GLONASS-K2 satellite R26 also broadcasts additional CDMA signals on L1 and L2. However, the inherent incompatibility between satellite clock bias products generated through traditional dual-frequency reference frequencies and multi-frequency observations, defined as inter-frequency clock bias (IFCB), diminishes the positioning accuracy of multi-frequency uncombined precise point positioning (UC-PPP). This contribution systematically investigates the time-varying characteristics of IFCB estimates for new GLONASS-M+/K1B/K2 satellites and examines the impact of L3 phase center offset (PCO) errors on IFCB estimation. Four experimental configurations are designed to quantify the effects of IFCB and L3 PCO errors on GLONASS-only triple-frequency UC-PPP results. Results indicate that considering L3 PCO errors renders the IFCB of GLONASS-M + satellites and GLONASS-K2 satellite R26 negligible. However, persistent sub-0.2-m periodic oscillations with evolving cyclic patterns characterize the IFCB series of GLONASS-K1B satellites R11 and R25. When only correcting for L3 PCO errors in GLONASS-only triple-frequency UC-PPP, significant systematic deviations in the L3 phase residuals of R25 remain, ranging from − 0.04 to 0.04&#xa0;m. Correcting IFCB and L3 PCO errors concurrently achieves the optimum performance among the four strategies, with average root mean square (RMS) values of positioning errors decreasing to 0.83, 1.51, and 2.68&#xa0;cm in the North, East, and Up directions, respectively, corresponding to 60.3%, 63.2%, and 64.1% accuracy gains over the conventional UC-PPP strategy, and enabling 78.17% of solutions to converge within 45&#xa0;min. Therefore, we emphasize the importance of simultaneous application of IFCB and precise L3 PCO corrections for high-precision GLONASS triple-frequency UC-PPP.</p>

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Characteristics of inter-frequency clock bias for new GLONASS-M+/K1B/K2 satellites and its contribution to uncombined PPP

  • 期刊论文

  • 发表日期：

    2025年12月23日

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  • Baoqi Lin,
  • Xinyun Cao,
  • Yulong Ge,
  • Fei Shen

摘要

All GLONASS-M+/K1B/K2 satellites are capable of transmitting legacy L1 and L2 signals based on frequency division multiple access (FDMA) modulation and new L3 signal based on code division multiple access (CDMA) modulation. The new-generation GLONASS-K2 satellite R26 also broadcasts additional CDMA signals on L1 and L2. However, the inherent incompatibility between satellite clock bias products generated through traditional dual-frequency reference frequencies and multi-frequency observations, defined as inter-frequency clock bias (IFCB), diminishes the positioning accuracy of multi-frequency uncombined precise point positioning (UC-PPP). This contribution systematically investigates the time-varying characteristics of IFCB estimates for new GLONASS-M+/K1B/K2 satellites and examines the impact of L3 phase center offset (PCO) errors on IFCB estimation. Four experimental configurations are designed to quantify the effects of IFCB and L3 PCO errors on GLONASS-only triple-frequency UC-PPP results. Results indicate that considering L3 PCO errors renders the IFCB of GLONASS-M + satellites and GLONASS-K2 satellite R26 negligible. However, persistent sub-0.2-m periodic oscillations with evolving cyclic patterns characterize the IFCB series of GLONASS-K1B satellites R11 and R25. When only correcting for L3 PCO errors in GLONASS-only triple-frequency UC-PPP, significant systematic deviations in the L3 phase residuals of R25 remain, ranging from − 0.04 to 0.04 m. Correcting IFCB and L3 PCO errors concurrently achieves the optimum performance among the four strategies, with average root mean square (RMS) values of positioning errors decreasing to 0.83, 1.51, and 2.68 cm in the North, East, and Up directions, respectively, corresponding to 60.3%, 63.2%, and 64.1% accuracy gains over the conventional UC-PPP strategy, and enabling 78.17% of solutions to converge within 45 min. Therefore, we emphasize the importance of simultaneous application of IFCB and precise L3 PCO corrections for high-precision GLONASS triple-frequency UC-PPP.