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。
The air route network,which supports all the flight activities of the civil aviation,is the most fundamental infrastructure of air traffic management system.In this paper,we study the Chinese air route network (CARN) within the framework of complex networks.We find that CARN is a geographical network possessing exponential degree distribution,low clustering coefficient,large shortest path length and exponential spatial distance distribution that is obviously different from that of the Chinese airport network (CAN).Besides,via investigating the flight data from 2002 to 2010,we demonstrate that the topology structure of CARN is homogeneous,howbeit the distribution of flight flow on CARN is rather heterogeneous.In addition,the traffic on CARN keeps growing in an exponential form and the increasing speed of west China is remarkably larger than that of east China.Our work will be helpful to better understand Chinese air traffic systems.
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.
