适用于北斗混合星座的相对定位随机模型建模策略

Stochastic modeling strategy for BDS hybrid constellation in relative positioning

为提高模糊度解算成功率和基线解精度,提出适用于北斗的相对定位随机模型建模策略,即混合随机建模策略。采用最小二乘方差分量估计方法对北斗单差观测量方差进行估计。对处于不同高度的三轨道卫星观测量方差分别建模:对地球静止轨道卫星观测量方差采用载噪比模型建模,对倾斜地球同步轨道卫星和中地球轨道卫星观测量方差均采用仰角模型建模。根据不同模型实时组建观测量的随机模型。试验结果表明:相比于采用传统简化模型和单一的仰角或载噪比模型,混合随机模型能更加真实地反映不同卫星观测量的随机噪声特性,模糊度解算成功率和相对定位精度均有提高,总体性能最优,因而能更好地适用于北斗系统。

In order to improve the integer ambiguity resolution success-rate and the baseline precision,a strategy of stochastic modeling for precise relative positioning aimed at hybrid constellation BDS was proposed,namely the hybrid stochastic modeling strategy.In the new strategy,variances of single-difference observations were estimated with the least-squares variance component estimation.After that,the observation variances of different orbits satellites were fitted with different models,carrier-to-noise ratios dependent model was used to fit the observation variances of geostationary earth orbit satellites,and two individual elevation-dependent models were used to fit observation variances of inclined geosynchronous satellite orbit and medium earth orbit satellites.Then the stochastic model of observation model was constructed in real time with these different fitted models.The experimental results reveal that,when compared with the traditional,simplified model and the sole elevation or carrier-to-noise ratios model,the proposed hybrid stochastic model is more realistic in reflecting the noise property of observations of different orbits satellites.And it has an overall better performance in integer ambiguity resolution success rates and relative positioning precision.Hence,the hybrid stochastic model is more suitable for BDS in high precision positioning applications.