The Fractional Cycle Bias (FCB) product is crucial for the Ambiguity Resolution (AR) in Precise Point Positioning (PPP). Different from the traditional method using the ionospheric-free ambiguity which is formed by the Wide Lane (WL) and Narrow Lane (NL) combinations, the uncombined PPP model is flexible and effective to generate the FCB products. This study presents the FCB estimation method based on the multi-Global Navigation Satellite System (GNSS) precise satellite orbit and clock corrections from the international GNSS Monitoring and Assessment System (iGMAS) observations using the uncombined PPP model. The dual-frequency raw ambiguities are combined by the integer coefficients (4,− 3) and (1,− 1) to directly estimate the FCBs. The details of FCB estimation are described with the Global Positioning System (GPS), BeiDou-2 Navigation Satellite System (BDS-2) and Galileo Navigation Satellite System (Galileo). For the estimated FCBs, the Root Mean Squares (RMSs) of the posterior residuals are smaller than 0.1 cycles, which indicates a high consistency for the float ambiguities. The stability of the WL FCBs series is better than 0.02 cycles for the three GNSS systems, while the STandard Deviation (STD) of the NL FCBs for BDS-2 is larger than 0.139 cycles. The combined FCBs have better stability than the raw series. With the multi-GNSS FCB products, the PPP AR for GPS/BDS-2/Galileo is demonstrated using the raw observations. For hourly static positioning results, the performance of the PPP AR with the three-system observations is improved by 42.6%, but only 13.1% for kinematic positioning results. The results indicate that precise and reliable positioning can be achieved with the PPP AR of GPS/BDS-2/Galileo, supported by multi-GNSS satellite orbit, clock, and FCB products based on iGMAS.

中文翻译：

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基于国际GNSS监测和评估系统观测结果的GPS / BDS-2 /伽利略系统分数周期偏差的估计，使用非组合PPP模型

分数周期偏差（FCB）产品对于精确点定位（PPP）中的歧义度解决方案（AR）至关重要。与通过宽车道（WL）和窄车道（NL）组合形成的使用无电离层歧义的传统方法不同，未组合的PPP模型灵活有效地生成了FCB产品。这项研究提出了FCB估算方法，该方法基于国际GNSS监视和评估系统（iGMAS）观测值的多全球导航卫星系统（GNSS）精确的卫星轨道和时钟校正，并使用了未合并的PPP模型。双频原始模糊度由整数系数（4，−3）和（1，−1）组合以直接估计FCB。FCB估算的详细信息在全球定位系统（GPS）中进行了说明，北斗2号导航卫星系统（BDS-2）和伽利略导航卫星系统（伽利略）。对于估计的FCB，后验残差的均方根（RMS）小于0.1个周期，这表明浮点模糊度具有很高的一致性。对于三个GNSS系统，WL FCB系列的稳定性优于0.02个周期，而对于BDS-2，NL FCB的标准偏差（STD）大于0.139个周期。组合的FCB具有比原始系列更好的稳定性。对于多GNSS FCB产品，使用原始观测值演示了用于GPS / BDS-2 / Galileo的PPP AR。对于每小时的静态定位结果，使用三系统观测的PPP AR的性能提高了42.6％，但运动定位结果仅提高了13.1％。