Journal of Geodesy

, Volume 85, Issue 8, pp 457–473 | Cite as

ITRF2008: an improved solution of the international terrestrial reference frame

  • Zuheir AltamimiEmail author
  • Xavier Collilieux
  • Laurent Métivier
Open Access
Original Article


ITRF2008 is a refined version of the International Terrestrial Reference Frame based on reprocessed solutions of the four space geodetic techniques: VLBI, SLR, GPS and DORIS, spanning 29, 26, 12.5 and 16 years of observations, respectively. The input data used in its elaboration are time series (weekly from satellite techniques and 24-h session-wise from VLBI) of station positions and daily Earth Orientation Parameters (EOPs). The ITRF2008 origin is defined in such a way that it has zero translations and translation rates with respect to the mean Earth center of mass, averaged by the SLR time series. Its scale is defined by nullifying the scale factor and its rate with respect to the mean of VLBI and SLR long-term solutions as obtained by stacking their respective time series. The scale agreement between these two technique solutions is estimated to be 1.05 ± 0.13 ppb at epoch 2005.0 and 0.049 ± 0.010 ppb/yr. The ITRF2008 orientation (at epoch 2005.0) and its rate are aligned to the ITRF2005 using 179 stations of high geodetic quality. An estimate of the origin components from ITRF2008 to ITRF2005 (both origins are defined by SLR) indicates differences at epoch 2005.0, namely: −0.5, −0.9 and −4.7 mm along X, Y and Z-axis, respectively. The translation rate differences between the two frames are zero for Y and Z, while we observe an X-translation rate of 0.3 mm/yr. The estimated formal errors of these parameters are 0.2 mm and 0.2 mm/yr, respectively. The high level of origin agreement between ITRF2008 and ITRF2005 is an indication of an imprecise ITRF2000 origin that exhibits a Z-translation drift of 1.8 mm/yr with respect to ITRF2005. An evaluation of the ITRF2008 origin accuracy based on the level of its agreement with ITRF2005 is believed to be at the level of 1 cm over the time-span of the SLR observations. Considering the level of scale consistency between VLBI and SLR, the ITRF2008 scale accuracy is evaluated to be at the level of 1.2 ppb (8 mm at the equator) over the common time-span of the observations of both techniques. Although the performance of the ITRF2008 is demonstrated to be higher than ITRF2005, future ITRF improvement resides in improving the consistency between local ties in co-location sites and space geodesy estimates.


Reference systems Reference frames ITRF Earth rotation 



The ITRF activities are funded by the Institut Géographique National (IGN), France and partly by Centre National d’Etudes Spatiales (CNES). We are indebted to all Analysis and Combination Centers of the Technique Services of the four techniques who constantly provide data for ITRF solutions which would not exist without their valuable contributions. We are particularly grateful to all the institutions who provide the necessary budgets for the space geodesy observatories, which constitute the main ITRF foundation. Fruitful discussions and exchanges with DGFI group have been found very valuable for the benefit of the ITRF2008 project. We are grateful to R. Ferland, J-J. Valette, J. Griffith, S. McClusky and the DGFI group for their contribution to the GPS discontinuity list. Part of the work of Laurent Métivier is an IPGP contribution number 3125. We acknowledge useful comments and suggestions provided by two anonymous reviewers and Athanasios Dermanis which improved the content of this article.

Open Access

This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.


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© The Author(s) 2011

Open AccessThis is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License (, which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Authors and Affiliations

  • Zuheir Altamimi
    • 1
    Email author
  • Xavier Collilieux
    • 1
  • Laurent Métivier
    • 1
    • 2
  1. 1.Institut Géographique National, LAREGMarne-la-ValléeFrance
  2. 2.Institut de Physique du Globe de ParisUniversite Paris-DiderotParisFrance

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