GPS共视时间比对中的电离层时延改正问题

众所周知，GPS共视是目前国际上主要的时间传递比对技术，其中扣除电离层时延是很重要的一个方面。介绍了如何采用国际GPS服务中心(IGS-International GPS Service)公布的电离总电子含量(TEC-Total Electron Content)图来进行电离层时延改正。结果表明：对于单频GPS接收机，采用TEC图作电离层时延改正后的单站定时和共视比对精度比用理论模型作改正的精度有很大的提高。通过比较还表明，亚太地区的时间实验室之室的时间传递精度比欧美地区的要低，这可能是因为亚太地区用于测量TEC的IGS测站少，因而导致该地区的TEC的精度较低。

Ionospheric Time Delay Corrections for GPS Time Transfer

GPS common-view is still one of the most powerful tools in the TAI computation up to now.To improve the precision for GPS time transfer is becoming more and more important along with the continuous improving of the qualities of atomic clocks.The precision lies on a few effects among which ionospheric delay is an important one.The method of calculating the ionospheric delay using TEC-map is introduced.The results indicate that the precisions for single-station timing and GPS-CV(Common-View)time transfer after correcting the ionospheric delay with TEC-map are better than those with the theoretical model for single-frequency GPS receivers.Besides,the comparisions show that the precisions for time transfer between time labs in Asia-Pacific region are lower than those in Europe and America,which is probably because there are much less IGS stations to measure TEC so as to cause lower precisions of TEC for Asia-Pacific region.