基于一阶模型补偿的GNSS RTK参考站数据预报策略

针对相对定位过程中基准站通信中断的情况，本文作者提出了一种对基准站数据进行高精度预报，维持向参考站提供延迟差分修正信息的思路. 对影响全球卫星导航系统(GNSS)观测值预报的卫星星历误差、电离层、对流层等误差源进行分析，比较了各类误差源对延迟时长的敏感程度. 实验结果显示:预报误差随着预报时长增加线性累积，且与卫星高度角负相关；当高度角低于10°时，预报5 min造成的误差可达174.6 cm. 同时，为提高数据预报精度，利用一阶线性模型计算误差累积速率，并补偿至预报观测值. 补偿后，上述预报累积误差削弱至64.4 cm. 定位结果表明:当基准站数据缺失1 min时，经一阶线性模型补偿预报后，零基线实时定位(RTK)定位结果在，东(E)、北(N)、天(U)三个方向均方根误差(RMSE)分别为0.37 cm、0.41 cm、0.86 cm，较未补偿时提升71.1%、77.2%和90.0%；当预报延迟为5 min时，仍能保持cm级解算精度. 

Observation prediction strategy of GNSS RTK reference station based on first-order model compensation

In this paper, high-precision method to predict observations from reference station of real-time kinematic (RTK) is proposed, which may be caused by the interruption of reference station communication. The satellite ephemeris, ionosphere, troposphere and other error sources that affect the prediction of the Global Narigation Satellicte System (GNSS) observations are analyzed, and the sensitivity of various error sources to the length of delay is compared. Results show that the forecast error accumulates linearly as the delay increases, and is negatively correlated with the satellite elevation. When the elevation angle is lower than 10°, the error caused by the precise ephemeris forecast for 5 minutes can reach 174.6 cm. At the same time, the linear trend can be calculated when the reference station data is not missing which can be used to compensate predicted observations. Under the same conditions, cumulative error of compensated observation is reduced to 64.4 cm. The RTK positioning results show that when delay is 1 min, the RMS of the three directions of E, N, and U are 0.37 cm, 0.41 cm, and 0.86 cm respectively, which is 71.1%, 77.2% and 90.0% better than that without compensation. By comparison with 5 minutes’ delay, the centimeter-level accuracy can still be maintained.