Enhancing GAST D Availability by Using the Ionospheric Field Monitor

GNSS ground-based augmentation system (GBAS) approach service type (GAST) D is one of the GBAS which can support category II/III approach and landing based on single-frequency GPS and/or GLONASS. It has been shown that the availability of the GAST D service may not be sufficient in the ionospheric active regions such as low magnetic latitude region. Using the ionospheric field monitor (IFM) which has already been proposed for GAST C to improve the availability of GAST D service is proposed. The performance of the IFM for GAST D is evaluated by using a newly developed exhaustive simulations of residual differential error associated with the ionospheric anomaly and missed detection probability by taking the IFM into account. IFM can reduce the residual differential error associated with the ionospheric anomaly and improve availability of GAST D service in ionosphere active regions. The availability of 99% or more can easily achieved by IFM. The IFM locations to achieve availability of 99% or more is shown to be quite flexible. Thus, utilizing the IFM is a simple and effective way to achieve high availability of GAST D service in ionosphere active regions.