Nominal ionospheric delay gradient estimation at Suvarnabhumi airport, Thailand

Ground-Based Augmentation System (GBAS) allows high-precision aircraft landing based on Global Navigation Satellite System (GNSS) at large airports. However, non-uniform spatial ionospheric delay needs to be determined. In this work, we compute the nominal ionospheric delay gradients around Suvarnabhumi airport, Thailand. The utilized techniques involve Kalman filter and LAMBDA method. Based on the measurements on DOY 043 of 2015, we found that the ionospheric delay gradients are less than 20 mm/km. With the improved ambiguity ratio test to obtain higher success rate than previous works, the standard deviation σ
_VIG
is 5.27 mm/km.