An Investigation of the Effect of Ionospheric Models on Performance of Network-Based RTK GPS in Thailand

  • Charoenkalunyuta T.
  • Satirapod, C. C.
  • Li Y.
  • Rizos C.


Thailand established a Network-based Real Time Kinematic (NRTK) GPS system using the Virtual Reference Station (VRS) concept in 2008. Currently the Thai NRTK consists of 11 reference stations located in the central part of Thailand with average reference station spacing of about 60 km. (Charoenkalunyuta et al., 2012) suggested that the ionospheric bias is the main error source which degrades NRTK performance in Thailand since the rate of ambiguity-fixing is significantly decreased when an irregular ionospheric variation occurs. In this paper, the position performance of NRTK is tested with a large number of GPS observations (31 consecutive days) and different reference receiver spacing, 10-20, 30-50, 50-60 and 60-80 km, with the use of final Global Ionospheric Maps (GIM) from the Center for Orbit Determination in Europe (CODE) and all available Continuous GPS (CGPS) stations in the central part of Thailand. Test results indicate that the NRTK positioning performance is improved when the final GIM was used, especially in the case of large reference receiver spacing. Thus it is concluded that the final GIM can mitigate the ionospheric bias in the NRTK mode.

Author Biography

Charoenkalunyuta T.