非组合与组合PPP模型比较及定位性能分析

使用2011 10 10全球随纬度均匀分布的10个IGS测站的观测数据，分别采用非组合、组合PPP（precise point positioning）模型进行定位解算，详细对比分析了两种PPP模型的静态和动态定位精度和收敛速度，以及ZPD估计精度。实验结果表明,两种PPP模型均可实现水平方向mm~cm级，高程1~3 cm的静态定位精度；水平方向1~3 cm，高程方向4 cm左右的模拟动态定位精度，非组合L1和L2载波相位观测值残差只有传统模型中组合相位观测值残差的1/3~1/5，内符合精度更高。对于30 s采样率的观测数据，组合PPP静态定位平均收敛时间为23 min，动态为38 min；非组合PPP静态定位平均收敛时间为29 min，动态为71 min，后者的收敛时间均普遍长于前者。在ZPD估计方面，两种模型的估计精度相当，均可达6 mm左右。

Mathematic Model and Performance Comparison Between Ionosphere-free Combined and Uncombined Precise Point Positioning

In order to overcome the shortcomings( e.g. to amplify measurement noise, loss of half observations) of traditional ionosphere free PPP model, recently some researchers have proposed a new PPP model by using uncombined original non differenced carrier phase and pseudorange observations to implement PPP, which named uncombined PPP. In this paper, the advantages and disadvantages of both PPP models are analyzed in detail. Observations from 10 IGS tracking stations on October 10th in 2011 are used to demonstrate the static and simulated kinematic PPP positioning performance with respect to positioning accuracy, convergence time and ZPD estimation accuracy between two PPP models. The results show that for both combined and uncombined PPP model, daily static positioning accuracy of mm~cm in horizontal, 1~3 cm in vertical and a kinematic positioning accuracy of 1~3 cm in horizontal, about 4 cm in vertical can be achieved. Observation residuals in uncombined PPP model are smaller than that of combined PPP model. For static case, the average convergence time of uncombined PPP is 38 min which is longer than that of combined PPP, For kinematic case, the average convergence time of uncombined PPP is 33min longer than that of combined PPP. For ZPD estimation, an accuracy level of about 6mm can be achieved from both PPP models.