HR: 0815h
AN: G41A-02 INVITED    [Abstracts]
TI: Station Coordinates Combination Status and Contribution to ITRF2005
AU: * Ferland, R
EM: rferland@nrcan.gc.ca
AF: Natural Resources, Canada, 456 - 615 Booth Street, Ottawa, On. K1A 0E9, Canada
AB: Under the auspices of the International GNSS Service (IGS), the Reference Frame Working Group combines at Natural Resources Canada (NRCan) an accurate and consistent set of station coordinates, velocities and Earth Rotation Parameters (ERP) that are updated weekly. The consistency of these parameters is ensured by simultaneously combining them using their full variance-covariance information. The IGS Analysis Centers (ACs) (cod, emr, esa, gfz, jpl, mit, ngs, sio) provide the solutions used in the IGS weekly combination. The Global Network Associates Analysis Centers (GNAAC) (mit, ncl) also generate weekly combined solutions that include consistent station coordinates and ERPs. Those GNAAC solutions are used for comparisons and quality control of the IGS weekly solution. In recent weeks each AC has been contributing between about 50 and 250 station coordinates estimates. The combined product currently approaches 300 stations. Of those, between 40 and 110 are used for the current IGS reference frame realization of the ITRF2005 in each AC solution. The quality of the AC station coordinates solutions has improved significantly since they have started contributing in early 1996. This is due to the densification of the network of stations along with gradual improvements in station hardware and processing software. For recent solutions, the estimated noise (std. dev.) level between the AC weekly solutions and the different combined solutions varies between 1-3mm horizontally and 2-10mm vertically. More details about the statistics, their evolution and differences between the ACs will be presented. IGS weekly station coordinates and ERP combined products have also been contributed to the ITRF2005. Those weekly solutions were all recombined from the original AC contributions, going back to the beginning of 1996. The recombined solutions were edited for known problems (e.g. incorrect antenna heights and outliers). Several stations with short time span were also removed. A list of station coordinates discontinuities was also prepared, in collaboration with several individuals and contributed to the IERS. Since November 5, 2006 (GPS week 1400), the IGS has implemented a realization of ITRF2005. It includes mainly the change from relative to absolute antenna phase centers and an update of the selected reference frame stations for the new realization. An expected change of scale from about 3 ppb to -0.7 ppb caused by the phase center shift was observed.
DE: 1229 Reference systems
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Geodesy [G]
MN: 2007 Fall Meeting