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IERS Message No. 484                                     August 09, 2023
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DTRF2020 Release


Dear colleagues,

After providing a preliminary DTRF2020 solution in February of this
year, we are pleased to inform you that the final DTRF2020 has been
released today. It is available from Zenodo

https://doi.org/10.5281/zenodo.8220524

and via the new DTRF website http://dtrf.dgfi.tum.de which provides
information on DTRF2020 and on previous DTRF solutions.

The main innovations of the DTRF2020 computation strategy compared to
DTRF2014 are
- the consideration of all three consistently modeled components of the
  non-tidal loading (NTL) signal (atmospheric, hydrological and oceanic
  component) for all stations
- the approximation and consideration of post-seismic deformation (PSD)
  in station motions
- the realization of the DTRF2020 scale from VLBI and GNSS observations

The DTRF2020 computation is, like for its predecessors, based on a
2-step approach:

In step 1, a TRF solution is calculated for each technique, in which NTL
displacements are reduced from the input normal equations (NEQ), PSD is
approximated and reduced, outliers and discontinuities are detected and
taken into account, and station velocities are parameterized.

In step 2, the TRF (NEQ) of the techniques are combined to the DTRF2020
solution by introducing local tie and velocity conditions and by
realizing the datum of DTRF2020. Both, the pre-processing steps and the
combination is hence performed on normal equation level.

The DTRF2020 release comprises (please see the website and the solution
description for details):
- one SINEX file per technique (for coordinates only,
  full variance-covariance matrix)
- an EOP file in IERS 20 C04 format
- PSD approximation time series for the DTRF2020 period
- NTL displacements (CM-and CF-related) per station and component
- NTL offsets and trends removed a priori from the input NTL model
  time series
- station position resudial time series
- SLR translation time series
- a short solution description

We thank all the colleagues who analyzed the DTRF2020 preliminary
solution. Your feedback was very helpful to improve the DTRF2020
solution and publication. Any further feedback on the DTRF2020 solution
is very welcome and helpful to improve DTRF solutions also in the
future. In case, you have any questions, please do not hesitate to
contact us.

We thank all the Technique Services of the IAG, the IERS GGFC and the
ITRS Center for their great efforts in providing the input data and for
the good cooperation! We thank also the IERS Central Bureau for their
assistance regarding publication and communication.

Best regards,
on behalf of the DGFI-TUM ITRS CC team,
Manuela Seitz


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