北斗高精度相对定位选星方法研究

针对北斗系统中高轨卫星会带来较全球定位系统（global positioning system ，GPS）更为严重的法方程病态性这一问题，分析了双差载波相位观测方程系数矩阵对整周模糊度浮点解解算的影响，结合北斗系统三轨道星座混合的特点，研究了区域北斗高精度相对定位选星方法，以仰角最高的地球同步轨道（geostationary earth orbit， GEO）卫星作为参考星，优先选取仰角高于10°的中地球轨道（medium earth orbit，MEO）卫星，然后按照均匀分布的原则选取倾斜地球同步轨道（inclined geosynchronous satellite orbit，IGSO）卫星。通过对实测数据进行试验和分析，证明了该方法的正确性和合理性，在进行区域北斗高精度相对定位时，能在一定程度上改善法方程的病态性，使模糊度浮点解较快收敛至真值附近，有利于模糊度的快速正确固定。

Research on BDS satellite selection in high-precision relative positioning

In BeiDou navigation satellite system(BDS), high-orbit satellites would cause a worse ill-conditioned problem to normal equation when compared to global positioning system(GPS). Firstly, the effects brought by coefficient matrix of double-differential carrier phase observation equation on calculating float solution of integer ambiguity is analyzed. On this basis, combining characteristics of the hybrid constellation of BDS, a high-precision regional BDS relative positioning satellite selection method is studied. In this method, the geostationary earth orbit (GEO) satellites with the highest elevation is selected as the reference satellite, then medium earth orbit (MEO) satellites with elevation higher than 10 degrees are selected preferentially, and inclined geosynchronous satellite orbit (IGSO) ones are selected according to uniform distribution principle. The experiments indicate that the proposed method is correct and reasonable. In high-precision regional BDS relative positioning, the proposed method would alleviate the ill-conditioned problem to some extent and bring float solution of the integer ambiguity into a relatively rapid convergence, which contributes to fast and correct fixation of integer ambiguity.