Navigation and service

IUGG (1991) Resolution on the Conventional Terrestrial Reference System

The International Union of Geodesy and Geophysics,


the need to define a Conventional Terrestrial Reference System (CTRS) which would be unambiguous at the millimeter level at the Earth's surface and that this level of accuracy must take account of relativity and of Earth deformation, and


the resolutions on Reference Systems adopted by the XXIst General Assembly of the International Astronomical Union (IAU) at Buenos Aires, 1991,


the Reference System as defined by IAU at the XXIst General Assembly at Buenos Aires, 1991 and


the following definitions of the CTRS:

  1. CTRS to be defined from a geocentric non-rotating system by a spatial rotation leading to a quasi-Cartesian system,
  2. the geocentric non-rotating system to be identical to the Geocentric Reference System (GRS) as defined in the IAU resolutions,
  3. the coordinate-time of the CTRS as well as the GRS to be the Geocentric Coordinate Time (TCG),
  4. the origin of the system to be the geocenter of the Earth's masses including oceans and atmosphere, and,
  5. the system to have no global residual rotation with respect to horizontal motions at the earth's surface.

Created: 1 Jan 2001. Text provided by the former Central Bureau.

This Page

© 2013 - Federal Agency for Cartography and Geodesy. All rights Reserved