SIRGAS combination at DGFI-TUM

The SIRGAS reference network is weekly processed; station positions are daily computed, and the seven individual daily solutions corresponding to a GPS week are combined in one weekly solution. The SIRGAS stations are classified in a core network (SIRGAS-C), with a continental coverage, and several densification networks, which correspond to the national reference networks (SIRGAS-N). The SIRGAS-C core network is processed by DGFI-TUM. The SIRGAS-N national networks are computed by the Latin American SIRGAS Processing Centres. The loosely constrained weekly solutions individually calculated for the national networks are combined with the loosely constrained weekly solution calculated for the SIRGAS-C core network to obtain compatible station positions and velocities in a continental level.

In addition to process the SIRGAS-C network, DGFI-TUM is responsible for combining the core network with the individual solutions delivered by the other SIRGAS Processing Centres. The main characteristics of the DGFI-TUM combination strategy are:

  • Software: Bernese GNSS Software 5.2, Dach et al. 2015 (doi: 10.7892/boris.72297).
  • The individual solutions are reviewed/corrected for possible format problems, station inconsistencies, etc.
  • Constraints included in the normal equations delivered by the SIRGAS Processing Centres are removed.
  • The sub-networks included in the individual solutions are aligned to the IGS (International GNSS Service) Reference Frame and compared to each other to identify possible outliers.
  • Stations with large residuals (more than 10 mm in the N-E component, and more  than 20 mm in the height) are reduced from the normal equations.
  • Variances obtained after aligning the individual solutions to the IGS Reference Frame are analysed to estimate scaling factors for relative weighting of the individual solutions in the weekly combination.
  • Combination of the contributing normal equations for computing a loosely constrained weekly solution for station positions (a priori positions for all stations are constrained by +/-1 m). This solution is submitted to the IGS for the global polyhedron and it is stored for the computation of the SIRGAS multi-year solutions. The loosely constrained weekly combinations generated by DGFI-TUM for SIRGAS are called SIRwwww7.SNX.
  • Computation of a solution for station positions aligned to the IGS Reference Frame. Datum realization through the IGS weekly coordinates (igsyyPwwww.snx) of selected IGS reference rtations. This solution provides the final weekly station positions. The weekly combinations aligned to the IGS Regerence Frame generated by DGFI-TUM for SIRGAS are called siryyPwwww.snx (normal equations in the SINEX format) and siryyPwwww.crd (station positions).


Dr.-Ing. Laura Sanchez

80333 München
Tel. +49 89 23031-1295
Fax +49 89 23031-1240