区域卫星导航系统无电离层组合定位精度分析

The Positioning Precision Analysis with Ionosphere Free Combination of Regional Satellite Navigation System

电离层折射误差是卫星导航系统定位的主要误差源之一。目前使用最广泛、最有效的电离层折射误差改正技术是双频技术。区域卫星导航系统具有3个频率的观测数据,可以形成多种消除电离层一阶项的观测组合以及消除电离层二阶项的观测数据。文中假设各个频率上的观测噪声相同,推导了B1/B2,B1/B3和B2/B3三种消电离层一阶项组合的表达式,其噪声放大因子分别为2.899,3.527和14.286;推导了B1/B2/B3消电离层一阶项且噪声最小组合的表达式,组合系数分别为6.179,-3.826和-1.000,该组合的噪声放大因子为2.865;推导了消除电离层二阶项组合的表达式,组合系数分别为-0.263,-0.749和1.000,该组合的噪声放大因子为35.748。利用实测的伪距数据对5种组合的定位误差进行了计算。定位结果表明,消电离层一阶项且噪声最小的定位精度最高;B1/B2,B1/B3和B2/B3组合定位精度依次降低;B1/B2/B3消电离层二阶项组合虽然消除了电离层二阶项,但噪声放大了35.748倍,因此其定位精度最差。

Ionospheric delay error is one of the most primary factor in positioning with satellite navigation system.The most effective method on modifying this error is the technology of double frequency observation combination.Regional satellite navigation system is qualified with triple frequency phase observations, several combinations which remove one-order ionospheric effect an be formed, furthermore, the second-order ionospheric effect removed combination can be got. The noise of B1 / B2, B1 / B3 and B2 / B3 ionosphere free combination has been deduced on the assumption that the observations on different frequency have the same noise. The noise magnifying factor is2. 899,3. 527,14. 286 respectively. The first-order ionospheric effect removed combination which has the least noise has been deduced. The combination coefficient is 6. 179,- 3. 826,- 1. 000 respectively and the noise magnifying factor is 2. 865. The second-order ionospheric effect removed combination has been deduced. The combination coefficient is 6. 179,- 3. 826,- 1. 000 respectively and the combination noise is getting larger to 35. 748.The positioning results of five kinds of combination using real pseudorange observation have been analyzed and compared. The results show that the precision of first-order ionospheric effect removed and having the least noise combination is the best,the precision of B1 / B2,B1 / B3, B2 / B3 is reduced sequently. The precision of B1 / B2 / B3 ionosphere second-order free combination is the worst, because of the noise magnifying factor is 35. 748.