基于RTCA标准的WAAS和EGNOS广播星历差分完好性服务性能研究

为了提高GPS卫星导航系统服务性能,很多国家和地区建立了独立的星基增强系统(SBAS),通过提供广播星历差分与完好性增强信息,满足高精度高完好性用户使用需求。本文介绍了美国WAAS和欧洲EGNOS等星基增强系统的广播星历差分完好性信息电文编码格式,并对实际星基增强系统的广播星历差分与完好性电文进行解析。由于不同的星基增强系统采用的信息处理模式不同,针对WAAS和EGNOS两个不同地区建立的星基增强系统,对广播星历差分慢变改正／快变改正的变化特征进行了比较分析。研究了星基增强系统广播星历差分完好性信息用户使用算法,基于国际GNSS服务组织(IGS)提供的GPS实测数据,对WAAS系统和EGNOS系统的广播星历差分服务精度和完好性性能进行了对比分析。结果表明,WAAS系统的伪距单点定位精度约为1.2 m, EGNOS系统的伪距单点定位精度约为1.8 m,与GPS基本导航服务相比,伪距单点定位精度可提高约22％和16％。两个星基增强系统利用完好性电文计算的完好性保护限值大致相当,均在16 m以内,能够对定位误差进行包络。 

The Service Performance Research of WAAS and EGNOS Broadcast Ephemeris Differential Integrity Based on RTCA

To improve the service performance of GPS, many countries and regions have established independent GPS Satellite -Based Augment System(SBAS), providing the broadcast ephemeris differential integrity message to satisfy the high precision and the high integrity users’ needs. This paper introduced the message format of the broadcast ephemeris differential integrity message of SBAS such as WAAS and EGNOS, and analyzed the real broadcast ephemeris differential integrity message of SBAS. The long-time corrections and the fast corrections’change characteristic of the broadcast ephemeris are analyzed in different regions which have the different SBAS and different message processing modes. Based on the GPS data provided by the International GNSS Service (IGS), the algorithm of using the broadcast ephemeris differential integrity message of SBAS are studied, and the positioning accuracy and integrity service of WAAS and EGNOS are compared and analyzed. The result shows that the positioning accuracy of WAAS is about 1.2 m, and the positioning accuracy of EGNOS is about 1.8 m. Compared with GPS basic navigation service, the positioning accuracy of WAAS and EGNOS could be increased by about 22％ and 16％. The integrity protection limits calculated by WAAS and EGNOS are roughly equal, within 16 m, and the positioning error can be enveloped.