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SC 1.3b - South and Central America (SIRGAS)

Programme of Activities

  • Since the SIRGAS countries are improving their national reference frames by installing an increasing number of continuously operating GNSS stations, it is necessary to outline the best possible strategy for the appropriate integration of those frames into the continental one. This includes:
    • Promotion and divulgation of the IGS and IERS standards within the SIRGAS countries to ensure the adequate installation, maintenance and analysis of continuously operating GNSS stations.
    • Establishment of a SIRGAS National Processing Centre in all the member countries.
    • Refinement of the SIRGAS station hierarchy. At present, two classes are considered: core and densification stations (the establishment of other category is under consideration).
    • Promotion of the adequate usage of SIRGAS as reference frame by means of capacity building activities. This comprises SIRGAS schools on reference frames, scientific processing of GNSS data, atmospheric analysis based on the SIRGAS infrastructure, etc.
    • Experimental processing of the GLONASS observation data to identify a suitable analysis strategy and to evaluate if these results can be combined with the corresponding GPS products.
    • Promotion and implementation of real-time services based on the SIRGAS infrastructure to make available the reference frame to more users.
  • The kinematics of the SIRGAS frame is until now represented by lineal station movements (i. e. constant velocities). This representation is not precise enough due to existing seasonal variations in the station position time series and due to discontinuities caused by the frequent occurrence of seismic events in the SIRGAS region. According to this, it is necessary:
    • To model non-linear station movements within the reference frame computation;
    • To implement a methodology aiming at the precise transformation between diferent epochs and, in general, and between pre-seismic and post-seismic reference frame realizations in particular;
    • To evaluate the feasibility of computing and using near-real time reference frames instead of those based on epoch station positions and constant velocities.
  • The establishment of a unified vertical reference system continues being a big challenge of SIRGAS. The related activities concentrate on:
    • Continental adjustment of the national vertical networks in terms of geo-potential numbers.
    • Combined analysis of tide gauge registrations, GNSS positioning and satellite altimetry observations to determine the dynamic ocean topography at the classical vertical datums.
    • Determination of potential differences between the reference tide gauges and a global reference surface.
    • Stronger cooperation with the Sub-Commission 2.4b (Gravity and Geoid in South and Central America - GGSCA) to promote national initiatives regarding the modernization of the gravity reference networks and the computation of geoid models of high resolution.
  • Hourly SIRGAS ionospheric models (vTEC) based on the GNSS SIRGAS stations are generated since 2006 in a regular basis. The SIRGAS ionospheric model is being upgraded to include a better distribution of the electron density based on the assimilation of ground- and space-based GNSS observations. Besides, SIRGAS is developing a service for computing water vapour estimations.

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