GPS C/A-code time-transfer stability in Asia

It was known that stability of time transfer by GPS C/A-code time-transfer in Asia was worse than that in Europe and the United States. Main sources to degrade the stability are the receiver-position error and the ionospheric delay. The stabilities in Asia were worse than those in the Europe and the United States when using the total electron content (TEC) map by the Center for Orbit Determination in Europe (CODE), while the results compensated with measured ionospheric delay were compatible with those in other areas. We investigated the effect with the vertical position error of the receiver. It became clear that the time-difference term between the GPS time and the local time depended on the elevation and azimuth angles and the short-term stability was degraded due to the errors. When the magnitude of the error was less than a few meters, we could not discriminate the existence of the error due to other errors. However, some receiver coordinates in Asian laboratories seemed to include a error. These results encourage us to use the measured ionospheric delay and the adequate receiver coordinates in order to improve the stability of time transfer in Asia.