对GBAS精度性能进行了分析。分别按照基于码减载波(code minus carrier,CMC)和B值两种方法对GBAS基准站实际数据进行了分析。CMC分析结果和B值的分析结果一致表明,GBAS基准站的精度性能等级约为GAD-A2。CMC分析法与B值分析方法具有一些不同的特点。CMC需要使用双频观测量;B值只需要单频观测量。CMC消除了短周期的多路径效应,主要反映的是长周期的多路径效应;B值经过GBAS基准站接收机平均,反映了不同接收机组合的多路径综合效应,更能反映GBAS差分校正误差的实际影响。除此之外,CMC分析法与B值分析法的天空图可以直观地评估GBAS站址的多路径环境。
Receiver autonomous integrity monitoring(RAIM) provides integrity monitoring of global positioning system(GPS) for safety-of-life applications.In the process of RAIM, fault identification(FI) enables navigation to continue in the presence of fault measurement.Affected by satellite geometry, the leverage of each measurement in position solution may differ greatly.However, the conventional RAIM FI methods are generally based on maximum likelihood of ranging error for different measurements, thereby causing a major decrease in the probability of correct identification for the fault measurement with high leverage.In this paper, the impact of leverage on the fault identification is analyzed.The leveraged RAIM fault identification(L-RAIM FI) method is proposed with consideration of the difference in leverage for each satellite in view.Furthermore,the theoretical probability of correct identification is derived to evaluate the performance of L-RAIM FI method.The experiments in various typical scenarios demonstrate the effectiveness of L-RAIM FI method over conventional FI methods in the probability of correct identification for the fault with high leverage.
The high level of safety demand of civil aviation requests local area augmentation system (LAAS) extremely high navigation integrity performance. A new LAAS pseudo-range error overbound method is proposed in this paper to improve the integrity of LAAS. Firstly, a more practical pseudo-range error distribution model is established. Then, by calculating the relationship between the statistical uncertainty of the model parameter and the integrity risk, a new method is proposed to calculate the pseudo-range error over-bound model. This method can effectively reduce the inflation factor and the resulting conservativeness of the over-bound model. Comparative experiments show that the method proposed in this paper performs better and satisfies the requirements of real applications.
