GNSS observation outage occurs inevitably in various situations, e.g., automobile driving in urban environments. Although the ambiguity resolution (AR) significantly shortens the initialization time of precise point positioning (PPP), frequent re-initialization of PPP AR may be needed due to outages. The inertial navigation system (INS) can be used for acquiring highly accurate position information during GNSS outages. In the previous studies, the GPS PPP/INS with the ambiguity resolution model is proposed, and the experimental results confirm that the INS could facilitate the re-fixing of the interrupted GNSS ambiguity. Multiple GNSS can also be used to shorten the PPP convergence time. We compare the contribution of multi-GNSS and the INS to the ambiguity re-fixing during GNSS outage. Results show that the multi-GNSS, e.g., Galileo, GLONASS and BDS, without ambiguity resolution has little contribution to the re-fixing of GPS ambiguity in PPP/INS, while INS can provide highly accurate positioning results during the GNSS outages. The higher the accuracy of the predicted INS positioning, the lower the contribution of multi-GNSS to the re-fixing of the ambiguity in the PPP/INS. The finding is verified by a theoretical analysis, carborne experiment and shipborne experiment. Experiment results show that the re-fixing time is 43 s for GPS PPP and MEMS-grade INS coupled system in GNSS outage of 1 s. The re-fixing time of GPS is slightly changed when adding the multi-GNSS, e.g., Galileo, GLONASS and BDS, without the ambiguity resolution. However, by performing ambiguity resolution to the added GNSS system, the re-fixing time of PPP/INS is significantly reduced from 43 to 4 s. The reason is that, although the multi-GNSS provides little improvement on the accuracy of the ambiguity, it enlarges the number of the ambiguity parameter. The possibility of ambiguity resolution is increased due to the large candidate set of the ambiguity, which reduces re-fixing time.

GNSS观测中断不可避免地在各种情况下发生，例如在城市环境中的汽车驾驶中。尽管歧义分辨率（AR）大大缩短了精确点定位（PPP）的初始化时间，但由于断电，可能需要频繁重新初始化PPP AR。惯性导航系统（INS）可用于在GNSS中断期间获取高精度的位置信息。在先前的研究中，提出了具有模糊度解析模型的GPS PPP / INS，并且实验结果证实了INS可以促进对被中断的GNSS模糊度的重新固定。也可以使用多个GNSS来缩短PPP收敛时间。我们比较了GNSS中断期间多GNSS和INS对歧义修复的贡献。结果表明，例如伽利略（Galileo）等多GNSS，没有歧义度解决方案的GLONASS和BDS对PPP / INS中GPS歧义度的重新定位几乎没有贡献，而INS可以在GNSS中断期间提供高度准确的定位结果。预测的INS定位的准确性越高，多GNSS对重新固定PPP / INS中的歧义的贡献就越小。通过理论分析，车载实验和舰载实验验证了这一发现。实验结果表明，在GNSS中断1 s的情况下，GPS PPP和MEMS级INS耦合系统的重新固定时间为43 s。在添加多GNSS（例如伽利略，GLONASS和BDS）时，GPS的重新固定时间会稍有变化，而不会产生歧义。但是，通过对添加的GNSS系统执行歧义解析，PPP / INS的重新固定时间将从43 s显着减少到4 s。原因是，尽管多GNSS对模糊度的准确性几乎没有改善，但它却增加了模糊度参数的数量。由于歧义的候选集较大，因此歧义解决的可能性增加了，这减少了重新固定时间。