Space-geodetic techniques allow, on a global basis, a centimetric realization of a Conventional Terrestrial Reference System through a Conventional Terrestrial Reference Frame. These techniques are in particular: VLBI, LLR, SLR and GPS. The actual Terrestrial Reference Frame (TRF) needs global coverage of observing sites for describing the motion and deformation of the whole Earth. In addition to geodetic and Earth Rotation aspects, geophysical phenomena requiring a global TRF include tectonic motion and deformation, change in global sea level and post-glacial rebound. The work on the terrestrial frame of the International Earth Rotation Service (IERS) and in particular the implementation of its TRF, called ITRF and based on combination of several data sets coming from space-geodetic techniques, will be presented in terms of quality and internal consistency. This work will be viewed from the perspective of an International Global Network.
