Variation of Satellite Timing Group Delay in Beidou Regional Satellite Navigation System in 2019

As a significant part of GNSS navigation message, timing group delay is one of the main errors in GNSS applications such as navigation, positioning, timing and ionospheric estimation. DCB solution in One-TGD-fixed constraint condition is more suitable for Beidou regional satellite navigation system, in which the TGD parameter exit calibration value of a certain GEO satellite is fixed as the constraint condition. Based on the global ionospheric map provided by IGS as a reference, monthly TGD parameters in 2019 have been calculated to analyse the characteristics of satellite TGD changes. The results demonstrate that the stability of TGD parameters is from high to low in the order of GEO satellites, MEO satellites and IGSO satellites. The changes of all satellites in a year are within 1ns, and most of them are within 0.5 ns. Monthly changes in TGD-B1B2 are in -1.6 ~ 1.5ns, and TGD-B1B3 are in -1.4 ~ 1.2ns. TGD-B1B3 parameters are more stable than TGD-B1B2 parameters in monthly variation, with maximum changes in a month within 1.6ns for TGD-B1B2 and 1.3ns for TGD-B1B3, average changes in a month within 0.7ns for TGD-B1B2 and 0.5ns for TGD-B1B3.