The operational SIRGAS weekly solutions refer to the IGS reference frame valid at the time when the analysis of GNSS data is made. An IGS reference frame corresponds to a subset of ITRF positions and velocities for a selected set of GNSS reference stations used as the fiducial points for the determination of the IGS satellite orbits, satellite clocks offsets, and Earth orientation parameters as well as the corrections for the phase centre offsets and variations at both transmitting and receiving GNSS antennas. As globally there is no translation, rotation or scale difference between both ITRF and IGS reference frame, products referring to the latter are considered to be nominally in the ITRF. According to the current practice, the publication of a new ITRF is quickly followed by the release of an updated IGS reference frame solution, which profits from the improved ITRF solution and the update of the GNSS antenna phase centre models.
Changing reference frame solutions and analysis standards may introduce spurious artefacts and systematics in the station position time series. Therefore, to ensure reliability and long-term stability of geodetic reference frames, the historical geodetic data have to be reanalysed from time to time using a unified set of newest standards and conventions over the complete time span. In SIRGAS, two reprocessing campaigns have been performed so far:
The SIRGAS operational solutions (generated within the routine data analysis) are available at ftp.sirgas.org/pub/gps/SIRGAS/
SIRGAS-Repro1 results are available at ftp.sirgas.org/pub/gps/SIRGAS/REPRO1/
SIRGAS-Repro2 results are available at ftp.sirgas.org/pub/gps/SIRGAS/REPRO2/
Dr.-Ing. Laura Sanchez
Tel. +49 89 23031-1295
Fax +49 89 23031-1240