SC 1.2 - Global Reference Frames

WG 1.2.1 - External Evaluation of Terrestrial Reference Frames

Chair:  Xavier Collilieux (France)

The scientific community has recognized the need for an highly accurate terrestrial reference frame (TRF) for Earth Science applications. Although geodetic measurements are very precise, uncertainty in the modeling of the measurements and correlations between estimated parameters make it complicated to assess geocentric station coordinates. While a precision at a few millimeter level is thought to be achieved, it is delicate to supply a clear figure of the current coordinate accuracy. The reliability of the station velocities is notably essential to study climate changes. Any error in the rate of the origin and scale definition of the TRF will especially map directly into the station velocities and in other products such as sea level rise estimates.

The aim of the task force is to review all the methods that could be used to assess the accuracy of the origin, scale and orientation (and/or their time variations) of a Terrestrial Reference Frame. All the activities in which the adopted TRF has a quantitative influence will be studied to derive possible constraints on the TRF. Methods that involve datasets that have not been used to derive the TRF will be especially emphasized (tide gauges, gravity, geophysical models etc...). As an example, the quality of ITRF2008 will be investigated using various methods in order to derive the most complete error budget.


  • Investigate methods to evaluate TRF accuracy, especially TRF datum parameters.
  • Supply an assessment of ITRF2008 quality using all available relevant methods.

Specific program activities

  • Study all the activities in which the adopted TRF has a quantitative influence.
  • Maintain a bibliography about TRF evaluation with any type of data and model.
  • Evaluate the interest to derive external constraints on TRF datum fixation, i.e. on its origin, scale, orientation and their time evolutions.

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