Abstract The strategy used in the ITRF2008, the site distribution, ITRF2008 parameters accuracy and the improvement relative to ITRF2005 are introduced. IERS released ITRF2008 on May 31, 2010 and it is refined versions of the International Terrestrial Reference Frame based on four space geodetic techniques, VLBI, SLR, GPS and DORIS. The scale agreement between ITRF2008 and ITRF2005 solutions at epoch 2005.0 is estimated to be 1.05 ± 0.13 ppb and 0.049 ± 0.010 ppb/a respectively. The ITRF2008 orientation (at epoch 2005.0) and its rate are aligned to the ITRF2005. The differences of the origin components from ITRF2008 to ITRF2005 at epoch 2005.0 are: -0.5, -0.9 and -4.7 mm along the X, Y and Z axis respectively. The differences of Y and Z translation rate between these two frames are zero,the X translation rate is 0.3 mm/a. The formal error of these parameters are estimated to be 0.2 mm and 0.2 mm/a, respectively. The ITRF2008 origin accuracy over SLR observation period based on its agreement with ITRF2005 is considered to be less than 1 cm. ITRF2008 scale accuracy, considering the scale consistency between VLBI and SLR, within a common observation time span of two technologies is less than 1.2 ppb (8mm at the equator).
