The Ground Based Augmentation System (GBAS) is a local-area, airport-based augmentation of Global Navigation Satellite Systems (GNSSs) that provides precision approach guidance for aircraft. It enhances GNSS performance in terms of integrity, continuity, accuracy, and availability by providing differential corrections and integrity information to aircraft users. Differential corrections enable the aircraft to correct spatially correlated errors, improving its position estimation. Integrity parameters enable it to bound the residual position errors, ensuring safety of the operation. Additionally, a GBAS ground station continuously monitors and excludes the satellites affected by any system failure to guarantee the system integrity and safety. Among the error sources of GNSS positioning, the ionosphere is the largest and most unpredictable. Under abnormal ionospheric conditions, large ionospheric gradients may produce a significant difference between the ionospheric delay observed by the GBAS reference station and the aircraft on approach. Such a spatially decorrelated ionosphere could lead to hazardous unbounded position errors if undetected. Conventional GBAS solutions to mitigate this threat assume that the “worstcase" ionospheric gradient ever observed in the relevant region is always present, which is a very conservative assumption. This approach, which relies on the conservative ionospheric threat models derived for GBAS, maximizes integrity, often at the expense of availability and continuity, especially in geographic areas with highly active ionosphere. As opposed to assuming a permanent “worst-case” gradient, I propose the Network GBAS concept, in which several reference stations collaborate to monitor for actual ionospheric gradients. This concept consists of two main steps. First, the network detects the anomalous ionospheric gradients, estimates the gradient parameters, and transmits this information to the GBAS stations installed in its coverage area. Then, the GBAS stations replace the “worst-case” ...


    Access

    Download


    Export, share and cite



    Title :

    Network-based ionospheric gradient monitoring to support ground based augmentation systems



    Publication date :

    2022-07-15


    Remarks:

    TDX (Tesis Doctorals en Xarxa)



    Type of media :

    Theses


    Type of material :

    Electronic Resource


    Language :

    English



    Classification :

    DDC:    629