中长基线的BDS三频线性组合观测量优化

基于几何无关（geometry-free，GF）和电离层无关（ionosphere-free，IF）的三频原始载波线性组合观测量，由于消除了一阶电离层延迟项以及同卫星与测站间几何距离相关误差项的影响，可有效应用于中长基线模糊度解算。对适用于北斗卫星导航系统（BDS）中长基线模糊度解算的GF和IF线性组合观测量进行了研究和优化，通过对载波观测量与伪距观测量组合，得到噪声最小且基于GF和IF的宽巷组合观测量，然后将模糊度得到固定的两个载波组合观测量与原始载波观测量进行最优线性组合，得到具有最低噪声的基于GF和IF的窄巷组合观测量。该方法充分利用了所有载波及伪距观测量信息，并根据其噪声水平进行了加权优化，公式推导具有普遍性和代表性。通过三频实测基线数据进行了论证分析。结果表明，经过一段时间的平滑之后，宽巷和窄巷模糊度浮点解的偏差能收敛到0.5周以内，从而实现模糊度的快速准确固定。

BDS Triple Frequency Linear Combination Observation Optimization for Medium-Long Baseline

Linear combination of the triple original carrier based on geometry-free(GF) and ionosphere-free(IF) can eliminate the first-order ionospheric-delay item and some other error terms influenced by geometric-distance between the satellite and station, thus it can be effectively applied to ambiguity-resolution for medium-long baseline. In this paper, the GF and the IF linear combination observations were studied and optimized for BDS long-baseline ambiguity resolution. Carrier and pseudorange observations were used to get the combination observation with minimum noise and based on GF and IF character, and considering that the ambiguity-correct carrier phase observation has lower noise compared with pseudorange observation, two carrier combinations with ambiguity-fixed and original carriers were applied to get the third optimal GF and IF combination with the minimum noise.Observations including all pseudoranges and carriers were applied in different weight according to their noises. Finally, real data of BDS triple frequencies were applied to verify the feasibility of model in the experiment.The result showed that the deviation of WL and NL float ambiguity resolutions can be under 0.5 cycle after smoothed, then the fast and accurate ambiguity resolution is realized.