Regional densifications of the ITRF (i.e. EUREF in Europe, SIRGAS in Latin America, etc.) are necessary to provide a reliable accessibility to the global reference frame and to support the appropriate use of positioning and navigation techniques. The main objective of these regional densifications is to guarantee the consistency between terrestrial reference station positions and satellite orbits, which have to be determined in the same reference frame in order to exploit the high-precision of the measurements. Special care has to be given to the datum realization. Today, the reference frames are a set of fiducial stations with known epoch positions, which are transformed to other epochs by applying constant velocities, i.e. linear coordinate changes are considered only. Nevertheless, station positions show seasonal variations resulting mainly from a combination of geophysical loading. Ignoring these seasonal variations, and other non-lineal movements, may introduce large errors in the datum realization and the reference networks can be significantly deformed. These effects are larger in regional networks than in global ones. According to this, the main purposes of this task are to define the best strategy for the datum realization and observation combination within regional reference frames, and to improve the modelling and representation of their kinematics.
- Residuals in the up-component after a similarity transformation between the loosely constrained (non-deformed) solution of the SIRGAS Reference Frame for the GPS week 1505 and the same solution aligned to the IGS05 using (a) IGS05 station positions given in 2000.0 and transformed with constant velocities up to week 1505, and (b) station positions directly determined within the IGS weekly combination for week 1505.
Sánchez L., Seemüller W., Drewes H., Mateo L., González G., Silva A., Pampillón J., Martinez W., Cioce V., Cisneros D., Cimbaro S.
: Long-Term Stability of the SIRGAS Reference Frame and Episodic Station Movements Caused by the Seismic Activity in the SIRGAS Region.
In: Altamimi Z. and Collilieux X. (Eds.): Reference Frames for Applications in Geosciences, IAG Symposia 138: 153-161, DOI:10.1007/978-3-642-32998-2_24
Sánchez L., Seemüller W., Seitz M.
: Combination of the Weekly Solutions Delivered by the SIRGAS Processing Centres for the SIRGAS-CON Reference Frame.
In: Kenyon S., M.C. Pacino, U. Marti (Eds.), "Geodesy for Planet Earth", IAG Symposia, 136: 845-851, DOI:10.1007/978-3-642-20338-1_106
Sánchez L.: IGS Regional Network Associate Analysis Centre for SIRGAS (IGS RNAAC SIR). Report of activities 2011. In: Meindl, M., R. Dach, Y. Jean (Eds.), International GNSS Service, Technical Report 2011; Astronomical Institute, University of Bern, p. 107-115. Available at ftp://igs.org/pub/resource/pubs/2011_techreport.pdf., 2012