Currently, the SIRGAS (Geocentric Reference System for the Americas) is performed by a permanent GNSS network called SIRGAS- CON, where there are about 240 permanent stations in operation, distributed in South, Central Americas and Caribbean region. The SIRGAS Analysis Centers were established in order to systematically determine the SIRGAS-CON station coordinates, following the standards established internationally in order to support the maintenance of the system and the activities of the SIRGAS Working Group GT-I (Reference System). Since August 2008 the Coordination of Geodesy of the Brazilian Institute of Geography and Statistics - IBGE officially took over the activities of an analysis Center. This is a kind of daily work to which bigher and bigher dedication is given as the number of stations in the South American continent has been increasing rapidly in the recent years. Other results are coming out; the station coordinates time series, thus enabling the determination of the station displacements due to the movement of the earth crust, local movements such as subsidence and / or local crustal uplift caused by natural phenomena such as earthquakes, as well as seasonal effects caused by several factors. At the same time, IBGE also carried out the weekly combination of solutions from nine weekly SIRGAS Analysis Centers. This combination aims at comparing to the results to those obtained by DGFI (Deutsches Forschungsinstitut Geodätisches), which provides the final weekly solution from SIRGAS-CON network. Due to result accuracy, the change of any information in the processing can lead to certain changes in the coordinates and hence discontinuities in the time series of each station. Recently, on April 17, 2011 (GPS week 1632), the orbits (rapid and final fast), the corrections of the satellite clocks and model calibration of antennas provided by the International GNSS Service - IGS, started to be referred to the new IGS realization, named IGS08. Since then, thereafter, the GPS processing using IGS products will have their results referred to this new reference system, which may cause discontinuities in the coordinates. The paper aims at presenting the processing strategy currently in operation, as well as a new strategy to improve the results. Another aim is to present some results of weekly processing and combination carried out by IBGE, and also to clarify the changes with the adoption of the new version of the Global Reference Network GNSS solutions, the IGS08.
SIRGAS-CON Network; Analysis Center IBGE; IGS08
