Abstract
Satellite-based augmentation system (SBAS) is an integral part of modern-day aeronautical navigation.
Recently, the dual-frequency multi-constellation (DFMC) SBAS based on the L1 and L5 frequencies (1575.42
MHz and 1176.45 MHz) have received a wide attention. However, the ionosphere-free combination (IF) technique
used in DFMC SBAS brings about relatively higher noise levels compared with the L1 frequency-only
approach. Importantly, the suitable radius (distance) between the user and reference receivers needs to be investigated
for the preliminary SBAS corrections and performances. Therefore, in this work, we investigate the
long-term correction (LTC) parameters generated from three reference stations in Thailand. The positioning
performances of DFMC SBAS demo (GPS and Galileo satellites) are investigated. The positioning results are
calculated based on the single point positioning (SPP) algorithm. Using the estimated LTC parameter (radius of
~587 km) on quiet days, the positioning errors in horizontal and vertical directions are 1.38 and 2.59 m, respectively.
In addition, on disturbed days, the horizontal and vertical errors are 1.50 and 2.93 m, respectively. From
the study, the reference stations in the radius of ~600 km can be considered a suitable range for the DFMC
SBAS demo at Thailand location.
https://ror.org/055mf0v62 
