GPS carrier phase and precise point positioning time scale comparisons using different software packages

Precise point positioning (PPP) software combines dual frequency code and phase GPS observation data with precise information about the satellite clocks and orbits provided by the International GNSS Service (IGS). It is also a very interesting method for time metrology. Error sources like tropospherical path delay and site displacements have to be modeled or estimated, while the error induced by the first order ionosphere terms can be canceled due to the usage of both GPS frequencies. In case of long baselines the atmospherical effects dominate. Here the physical correction models become important. In this work we compare several precise point positioning (PPP) software packages and study not only the clock solution but also other estimated parameters like positions and zenith tropospheric zenith path delays in order to find the software that is most suitable for time transfer. Especially the repeatability of the position could be a good indicator for quality. We use Dicom GTR50 time and frequency transfer receivers connected to local time scale realizations on baselines with different lengths.