Notes on the post-seismic deformation (PSD) models.

The full equations of the parametric models used in the ITRF2014 generation are supplied in the pdf file "ITRF2014-psd-model-eqs-IGN.pdf".

The full PSD estimated parameters and their variances are provided in SINEX format, files:

- ITRF2014-psd-vlbi.snx
- ITRF2014-psd-slr.snx
- ITRF2014-psd-gnss.snx
- ITRF2014-psd-doris.snx

ITRF2014 solution provides the usual/classical estimates: station positions at a given epoch (2010.0, for ITRF2014), station velocities and EOPs.

A user who wants to compute the position of a station affected by post-seismic deformations at an epoch during the relaxation (non-linear) period should compute first the δX(t) which is the total sum of the PSD corrections. The user should read the model parameters (EQ epoch, model type, LOG or/and EXP, amplitude and relaxation time) in one of the following two files:

- SINEX file (ITRF2014-psd*.snx). These SNX files provided per technique contain the full information of the parametric models used in the ITRF2014 generation, including the variance-covariance information. It is strongly recommended to use these SNX files, especially if the user needs to compute the variance of the estimated corrections. Please refer to the equations in the pdf file "ITRF2014-PSD-model-eqs-IGN.pdf". A Fortran subroutine called "psdmatc.f" is provided which allows to compute the terms of the matrix used in the variance-covariance propagation equations.
- CATREF internal file (ITRF2014-psd*.dat). In this case a subroutine called "parametric.f" is provided that allows computing δX(t). An example of a subroutine called "psd-example.f" is provided that the user can adapt to his application AND insert his own routines at two places as indicated in the comment lines of the Fortran file. Please read the commentary lines in the provided Fortran files. Note that using CATREF internal files does not allow computing the variance-covariance matrix of δX(t).

The PSD files, Fortran routines and some numerical examples are available at the ITRF2014 ftp server:

`ftp itrf.ign.fr`

`cd pub/itrf/itrf2014`