北斗伪距码偏差对基线解算的影响分析

北斗二代系统伪距码中存在与高度角相关的系统性偏差，该偏差会影响高精度的数据处理。基于Melbourne-Wübbena（MW）组合，分别利用现有的伪距码偏差改正模型和实测基线的双差宽巷模糊度残差，分析了伪距码偏差对基线解算的影响。理论分析表明，随着基线长度的增加，伪距码偏差对MW组合确定双差宽巷模糊度的影响越来越大，对300 km基线的影响可达0.36周。实际算例表明，无论基线长短，地球同步轨道（geostationary earth orbit，GEO）卫星的双差宽巷模糊度残差中始终存在偏差；而对于倾斜地球同步轨道（inclined geostationary orbit，IGSO）和中轨（medium earth orbit，MEO）卫星而言，当基线小于300 km时，双差基本可以消除伪距码偏差，其双差宽巷模糊度固定率基本和GPS一致，但当基线超过300 km时，部分卫星的双差宽巷模糊度残差就会存在明显偏差，其双差宽巷模糊度固定率也较低，此时需考虑伪距码偏差的影响。

Influence of BDS Pseudorange Code Biases on Baseline Resolution

Pseudorange code biases will influence high precision data processing in BeiDou navigation satellite system (BDS). Based on Melbourne-Wübbena(MW) combination, we have analyzed the effect of code biases on baseline resolution according to the code biases correction models and the residuals of double differenced wide-lane ambiguity of baselines, respectively. The results show that the influence of code biases on double differenced wide-lane ambiguity resolution with MW combination is gradually obvious as the baseline becomes longer. Moreover, the impact on the 300 km baseline may reach up to 0.36 cycles. In addition, the results suggest that the code biases of geostationary earth orbit(GEO) have great influence over both short and long baselines. For inclined geostationary orbit (IGSO) and medium earth orbit (MEO), the code biases have little effect on baseline solution when the baseline is within 300 km, however, the residuals of wide-lane ambiguity of partial satellites have obvious biases when the baseline is over 300 km. Furthermore, the fixing rates of wide-lane ambiguity of these satellites are lower, so we should take into account the influence of code biases on baseline resolution at this time.