Modelling Environmental Loading Effects for Reference Frame Realizations

Joint with the IERS

Chair: Tonie van Dam (Luxembourg)

Vice-Chair: Anthony Mémin (Australia)


Terms of Reference

The accuracy and precision of current space geodetic techniques are such that displacements due to non-tidal surface mass loading are measurable. Many scientific studies have already considered atmospheric loading corrections at the observation level. The modeling of other non-tidal loading effects have been also investigated by various authors. In parallel, a posteriori corrections have been shown to slightly decrease the variance factor of a Terrestrial Reference Frame (TRF) multi-technique combination but the improvement at some sites was also counterbalanced by degradation at others.

There still exist open questions regarding the application of loading corrections for the generation of operational geodetic products, either a priori or a posteriori: accuracy of the models in all frequency bands - sub-daily band is the most important for a priori corrections -, too few studies regarding available loading model agreement have been carried out, proper mass conservation of all contributions and degree 0 of each contribution, methods that should be use for interpolating the loading displacements, required model resolution, reference loads that are or should be used for geodetic products, contribution of ice melting at high latitude which is not modeled in current continental water loading models. The optimal usage of loading models is still to be defined in all possible applications.

The goal of this working group is to study the optimal usage of load models for TRF utilization.



The principal objectives of the scientific work are to investigate optimal methods for applying load corrections for TRF development and usage, and to assemble specific recommendations for users. 


Specific program activities

  • Compare and assess differences between existing load models for a given effect
  • develop forward model of ice loading at high latitudes
  • monitor geocenter motion variations to identify possible accelerations
  • Maintain a bibliography on the available models and their evaluation.
  • Assessment of the propagation of loading model errors into the site coordinates and the ITRF.
  • Define whether models should be applied at the observation level or in the post-processing. In this case, define the best method (if any) to handle loading effects at the observation level (filtering?, interpolation etc…).
  • Tie results/findings to IERS conventions.
  • Collect user opinions about what signals they need in station position time series (loading corrected or not). 



  • Tonie van Dam (Luxembourg), Chair
  • Anthony Mémin (France), Vice-chair
  • Zuheir Altamimi (France)
  • Johannes Böhm (Austria)
  • Jean-Paul Boy (France)
  • Xavier Collilieux (France)
  • Robert Dill (Germany)
  • Pascal Gegout (France)
  • Matt King (Australia)
  • Anthony Mémin (France)
  • Laurent Métivier (France)
  • Gerard Petit (France)
  • Jim Ray (USA)
  • Leonid Vitushkin (Russia)
  • Xiaoping Wu (China)