Achievements and Challenges of SIRGAS

SIRGAS is the geocentric reference system for the Americas. Its definition corresponds to the IERS International Terrestrial Reference System (ITRS) and it is realized by a regional densification of the IERS International Terrestrial Reference Frame (ITRF). The SIRGAS activities are coordinated by three working groups: SIRGAS-WGI (Reference System) is committed to establish and maintain a continental-wide geocentric reference frame within the ITRF. This objective was initially accomplished through two continental GPS campaigns in 1995 and 2000, comprising 58 and 184 stations, respectively. Today, it is realized by around 130 continuously operating GNSS sites, which are processed weekly by the IGS Regional Network Associate Analysis Centre for SIRGAS (IGS-RNAAC-SIR). SIRGAS-WGII (Geocentric Datum) is primarily in charge of realising the SIRGAS geodetic datum in the individual countries, which is given by the origin, orientation and scale of the SIRGAS system, and the parameters of the GRS80 ellipsoid. SIRGAS-WGII is concentrating on promoting and supporting the adoption of SIRGAS in the Latin American and Caribbean countries by means of national densifications of the continental network. SIRGAS-WGIII (Vertical Datum) is dedicated to the definition and realization of a unified vertical reference system within a global frame. Its central purpose is to refer the geopotential numbers (or physical heights) in all countries to one and the same equipotential surface (W-0), which has to be defined globally. This includes also the transformation of the existing height datums into the new system.