基于卫星监视几何精度因子的UDRE值估计方法

星基增强导航系统(SBAS,Satellite Based Augmentation System)通过向用户提供用户差分距离误差(UDRE,User Differential Range Error),来保证广播星历和星钟改正数的精度并增强用户的完好性性能.给出了一种用于主控站的UDRE计算方法,提出了卫星监视几何精度因子(SSDOP,Satellite Surveillance Dilution of Precision)的概念.基于UDRE和SS-DOP的表达式,通过数学推导发现UDRE受到SSDOP和限制因子的影响,而限制因子可以用其统计平均值0.7438来替代,建立了由SSDOP估计UDRE的表达式.仿真结果表明:利用SS-DOP估计出的UDRE值,其误差不超过0.8 m,能够反映出当前卫星UDRE的特性,可以作为用户在无法接收完好性信息时快速推算UDRE的一种可行手段.

UDRE estimation approach based on satellite surveillance dilution of precision

Satellite based augmentation system (SBAS) provides user differential range error (UDRE) which guarantees satellite ephemeris and clock correction accuracies to the users to enhance their integrity. A method of calculating UDRE only used in the master station was introduced, then a concept of satellite surveillance dilution of precision (SSDOP) was proposed to reflect the effect of changing the reference stations- distribution on the satellite ephemeris and clock correction accuracies. A mathematical equation was deduced from the SSDOP and UDRE expressions, and from the view of the equation the UDRE was infected by SSDOP and restriction factor which could be replaced by, 0.7438, its statistic average value.The equation based upon SSDOP to estimate UDRE was established. The simulation results show that the estimation value of UDRE based on SSDOP can reflect the performance of the current UDRE and its accuracy is less than 0.8m. This approach can be used as an alternative method to calculate the UDRE when the user can-t receive the integrity information broadcasted by SBAS.