Rapid

Introduction

• Rapid solutions use all available 24h sessions from 1984 to present, and the solution is updated twice per week.
• The combination is based on the addition of normal equation matrices, and makes use of datum-free normal equation matrices of VLBI sessions which are provided as SINEX files.

• Two combined series are available:

  • Combined series (dX, dY):
    The nutation offsets are dX, dY referred to IAU2006 precession-nutation model excluding free core nutation

  • Combined series (dPsi, dEps):
    The nutation offsets are dPsi, dEps referred to IAU2000A precession-nutation model excluding free core nutation

Combination Procedure

1. Matrices are transformed into the mean epoch of all contributions by using the respective earth orientation parameter rates, before accumulating the individual normal equation matrices.
2. Individual normal equation matrices are then transformed to a common set of apriori values for station coordinates and earth orientation parameters.
3. Weighting factors determined by variance component estimation are applied to the normal equation systems.
4. The datum-free normal equation matrices are accumulated.
5. Earth orientation parameters are estimated by fixing all station components to their ITRF2008 values.

6. Comparisons for the purpose of quality control are carried out:

• internal comparisons of the individual solutions are made with respect to the combined solution,

• external comparisons are carried out with the earth orientation parameters of the IGS Final Combined Solution (igs00p03.erp) as well as with the IERS C04 (eopc04.62-now) earth orientation parameter series.