抄録
The Ionospheric modeling is a required step for the implementation of the Ground Based Augmentation System (GBAS), at low latitude zones this is particularly challenging due to the known ionospheric disturbances and their effects. Previously, single constellation ionospheric modeling using the time-step method has been performed in low latitudes, yet, as constellations grow, the multi-constellations assessment of this modeling including both Medium Earth Orbit (MEO) and Inclined Geosynchronous Orbit (IGSO) satellites is necessary considering the orbital characteristics of IGSO affecting the time-step method. In this study, the time-step method is applied to evaluate the nominal ionospheric conditions in the vicinity of an airport using GPS and BDS MEO constellations, additionally, we evaluate the case when IGSO satellites are included. These tests were based on the use of selected receivers from the National Continuously Operating Reference Stations Data Center (NCDC) of Thailand, which is a robust, multi-stakeholder network of GNSS receivers distributed throughout the kingdom. The results showed that the ionospheric modeling using GPS and BDS MEO agree with each other under nominal conditions, however, when IGSO satellites are to be included, some considerations in the time-step method should be taken due to its orbital characteristics.
https://ror.org/055mf0v62 
