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<p>Integer precise point positioning (IPPP) has been shown to achieve high accuracy time and frequency transfer based on GPS. However, the contribution of multiple constellations to the frequency stability of IPPP time links, especially in the long term, has not been fully investigated. At the same time, fractional discontinuities at day boundaries resulting from daily processing strategies threaten both frequency stability and integer-cycle day boundary alignment. In this study, we integrate GPS, Galileo and BDS observations over 30&#xa0;days to generate post-processed IPPP time links. We find that frequency stability improves by up to 25% from 300&#xa0;s to half a day due to better satellite geometry of multi-GNSS, corresponding to a TDOP value of 0.7 for GPS/Galileo/BDS and 1.5 for GPS alone. To deal with fractional discontinuities, we propose single-day IPPP processing, while linking positions and tropospheric delays near day boundaries. We validate this approach as powerful tool for very long data batches, typically longer than 50&#xa0;days. In the experiment, constraining positions and tropospheric delays reduced the number of fractional discontinuities larger than 0.2&#xa0;ns from two to zero, but our results also show that inadequate constraints may introduce instabilities into the time links at the day boundaries. In comparison, multi-day IPPP processing based on aligned satellite orbit and clock products is verified to thoroughly eliminate day boundary discontinuities without introducing any additional errors.</p>

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Continuous time and frequency transfer achieved by multi-day GPS/Galileo/BDS integer precise point positioning

  • 期刊论文

  • 发表日期：

    2025年4月16日

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  • Jiang Guo,
  • Pascale Defraigne,
  • Elisa Pinat

摘要

Integer precise point positioning (IPPP) has been shown to achieve high accuracy time and frequency transfer based on GPS. However, the contribution of multiple constellations to the frequency stability of IPPP time links, especially in the long term, has not been fully investigated. At the same time, fractional discontinuities at day boundaries resulting from daily processing strategies threaten both frequency stability and integer-cycle day boundary alignment. In this study, we integrate GPS, Galileo and BDS observations over 30 days to generate post-processed IPPP time links. We find that frequency stability improves by up to 25% from 300 s to half a day due to better satellite geometry of multi-GNSS, corresponding to a TDOP value of 0.7 for GPS/Galileo/BDS and 1.5 for GPS alone. To deal with fractional discontinuities, we propose single-day IPPP processing, while linking positions and tropospheric delays near day boundaries. We validate this approach as powerful tool for very long data batches, typically longer than 50 days. In the experiment, constraining positions and tropospheric delays reduced the number of fractional discontinuities larger than 0.2 ns from two to zero, but our results also show that inadequate constraints may introduce instabilities into the time links at the day boundaries. In comparison, multi-day IPPP processing based on aligned satellite orbit and clock products is verified to thoroughly eliminate day boundary discontinuities without introducing any additional errors.