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  ITRF2014 : computation strategy

The strategy adopted for the ITRF2014 generation consists in the following steps:

  • Apply minimum constraints equally to all loosely constrained solutions: this is the case of SLR weekly solutions;
  • Apply No-Net-Translation and No-Net-Rotation conditions to IVS solutions provided in the form of Normal Equation;
  • Use as they are minimally constrained solutions: this is the case of IGS and IDS weekly solutions;
  • Form per-technique long-term solutions (TRF + EOP), by rigorously staking the time series, solving for station positions, velocities, EOPs, annual and semi-annual signals, and 7 transformation parameters for each daily or weekly solution w.r.t the per-technique cumulative solution. During the stacking process:
    • Annual and semi-annual signals are estimated for stations with sufficient time-spans;
    • Post-seismic deformation (PSD) model corrections were applied to Earthquake (EQ) sites, prior to the construction of the normal equation of the stacking of the time series;
  • Identify and reject outliers and properly handle discontinuities using piece-wise linear function approach and PSD models for EQ sites. The discontinuity files used for each one of the 4 techniques are found here.
  • Combine the per-technique cumulative solutions adding local ties in co-location sites.

This last step yields the final ITRF2014 solution comprising station positions, velocities and EOPs. Note that EOPs start in the early eighties with VLBI and SLR, while DORIS contribution starts from 1993 and GPS from 1994.0.







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