ITRF2008: an improved solution of the international terrestrial reference frame

Abstract

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 sessionwise 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. 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.

Nonlinear subsidence at Fremantle, a long‐recording tide gauge in the Southern Hemisphere

“…As with the groundwater data, all data up until 2013.0 were collated and analyzed, although the GPS time series at PERT was truncated at 2012.0 because a lightning strike caused a 6 month data gap followed by a new equipment installation, resulting in an offset that is poorly determined. The PERT and HIL1 CGPS data were processed daily in precise point positioning mode as described in Williams and Penna [2011], except the GIPSY 6.2 software was used, JPL (Jet Propulsion Laboratory) repro1 orbits and clocks were held fixed, and the fiducial-free outputs were transformed to the IGS08 realization of ITRF2008 [Altamimi et al, 2011].…”

Realizing a terrestrial reference frame using the Global Positioning System

“…The current standard for the most demanding scientific applications is designated the International Terrestrial Reference Frame (ITRF), updates for which are published regularly by the ITRF Center of the International Earth Rotation and Reference Systems Service (IERS) [Petit and Luzum, 2010;Altamimi et al, 2011]. Each revision of the ITRF represents a practical, and thus imperfect, realization of an idealized International Terrestrial Reference System (ITRS).…”

Observing and understanding the Earth system variations from space geodesy

“…Nowadays, continuous GPS observations can provide high precision 3-dimensional coordinate time series, which can estimate low degree gravity field coefficients (Wu et al, 2006;Jin and Zhang, 2012). Here, the GPS coordinates time series from ITRF2008 solutions (Altamimi et al, 2011) are used to estimate geocenter and J 2 together with OBP (ocean bottom pressure) and GRACE, respectively, which show good agreement with SLR solutions and geophysical models estimates in seasonal, intraseasonal and interannual variations. For example, Fig.…”