北斗/GPS抗差移动窗口定权位移探测

蠕变状态下Kalman定位精度通常与观测值方差有极大关系,BDS(BeiDou Navigation Satellite System)/GPS组合观测值方差易受观测值权比精确度的影响。为了提高位移探测精度、缩短初始坐标收敛时间及降低监测成本,本文采用时钟同步双天线BDS/GPS接收机,在构建单频单差组合定位模型基础上,分别对GPS和BDS观测值等价权进行抗差处理,利用引入时间相关遗忘因子的Helmert方差估计,精确确定GPS与BDS观测值权比,最后通过实时更新观测值方差,实现扩展Kalman滤波的逐历元定位。试验结果表明,针对短基线(1km),BDS/GPS抗差精密定权Kalman方法可显著缩短初始坐标收敛时间,位移探测精度可达到亚毫米级,位移收敛速率与移动窗口参数基本成反比关系,适用于具有蠕变特征形变体的监测。

BeiDou/GPS Displacement Detection Using Robust Weighting Based on Moving Window

The positioning accuracy of Kalman model under creep deformation condition is closely related to the observation variance, which can be affected by the accuracy of weight ratio of GPS and BDS observations.To improve displacement detection accuracy, shorten convergence time of initial coordinate and reduce monitoring cost, firstly the BDS/GPS single-frequency single-difference combination model is set up by using clock-synchronized dual-antenna BDS/GPS receiver.Then the equivalent weights of GPS and BDS observations are robustly determined respectively, and the Helmert variance component estimated by introducing time-correlated forgetting factor is used to achieve the precise weight ratio between GPS and BDS observations.Finally the coordinates are calculated using the extended Kalman filter by updating observed variance in real-time.According to the experiment, for the short baseline (1km), BDS/GPS robust precise weighting Kalman method can shorten convergence time of initial coordinate significantly, which is suitable for monitoring the deformation body with creep characteristics, and the displacement detection accuracy can reach sub-millimeter level.Moreover the displacement convergence rate is inversely related to the length of moving window approximately.