Daily and weekly coordinates solutions of GNSS permanent stations operating within EPN network allows to track long-term changes of coordinates caused e.g. by the local and global movements of tectonic plates. They are therefore an excellent tool for testing stability and repeatability of stations position. The article presents an analysis of coordinates changes of selected reference stations based on weekly EPN solutions. In addition the author proposes parameters of approximating function by assuming an existence of periodic, annually repeatable trend. The author performed also an independent fitting function for two different periods of two ITRF frames of routine time analysis and reprocessing.
The International GNSS Service (IGS) provides high-accuracy clock products for both GNSS satellites and stations. On board of each GNSS satellite are located 3–4 atomic oscillators. In the case of CORS oscillators, the majority of them are equipped with internal oscillators and a part uses external, high-rate clocks. In the IGS network there are four types of external oscillators: quartz, rubidium, caesium and H-maser. These CORS are often reference stations for precise GNSS measurements or for time transfer. In this paper the author provides analyses of the internal and external stability of the reference stations oscillators via the usage of Allan variations. The results show a strong advantage of the external clocks over internal ones by about five orders of magnitude.