ITRF2000: A new release of the International Terrestrial Reference Frame for earth science applications

Abstract

[1] For the first time in the history of the International Terrestrial Reference Frame, the ITRF2000 combines unconstrained space geodesy solutions that are free from any tectonic plate motion model. Minimum constraints are applied to these solutions solely in order to define the underlying terrestrial reference frame (TRF). The ITRF2000 origin is defined by the Earth center of mass sensed by satellite laser ranging (SLR) and its scale by SLR and very long baseline interferometry. Its orientation is aligned to the ITRF97 at epoch 1997.0, and its orientation time evolution follows, conventionally, that of the no-net-rotation NNR-NUVEL-1A model. The ITRF2000 orientation and its rate are implemented using a consistent geodetic method, anchored over a selection of ITRF sites of high geodetic quality, ensuring a datum definition at the 1 mm level. This new frame is the most extensive and accurate one ever developed, containing about 800 stations located at about 500 sites, with better distribution over the globe compared to past ITRF versions but still with more site concentration in western Europe and North America. About 50% of station positions are determined to better than 1 cm, and about 100 sites have their velocity estimated to at (or better than) 1 mm/yr level. The ITRF2000 velocity field was used to estimate relative rotation poles for six major tectonic plates that are independent of the TRF orientation rate. A comparison to relative rotation poles of the NUVEL-1A plate motion model shows vector differences ranging between 0.03°and 0.08°/m.y. (equivalent to approximately 1-7 mm/yr over the Earth's surface). ITRF2000 angular velocities for four plates, relative to the Pacific plate, appear to be faster than those predicted by the NUVEL-1A model. The two most populated plates in terms of space geodetic sites, North America and Eurasia, exhibit a relative Euler rotation pole of about 0.056 (±0.005)°/m.y. faster than the pole predicted by NUVEL-1A and located about (10°N, 7°E) more to the northwest, compared to that model.

Quantification of strain rate in the Western Alps using geodesy: comparisons with seismotectonics

“…A few sites of the Alpine network and the Rhine graben were re-measured in 2000 and 2001. In our approach we use the methodology described in Altamimi et al (2002), which applies reference frame constraints simultaneously for all individual solutions. The consistency of the final solution is ensured through common reference sites.…”

Impact of GPS satellite antenna offsets on scale changes in global network solutions

“…[2] The GPS technique can be a viable tool for defining and maintaining the global Terrestrial Reference Frame (TRF) either alone or in combination with other techniques [Altamimi et al, 2002;Heflin et al, 2002]. However, the GPS derived scale is highly correlated with the offset of the transmitter antenna phase center.…”

“…[3] A recent investigation by Zhang et al [2004], reprocessing GPS data over the last 10 years using the IGS standard satellite antenna phase center offsets, showed a rapid scale change of about 1 ppb during the year 2000 while aligning the GPS solutions to the International Terrestrial Reference Frame 2000 (ITRF2000) [Altamimi, 2002]. This unreasonable scale change (see Figure 1) is highly correlated with the launches of five new block IIR satellites during this time period, and seems therefore to be connected to the satellite antenna offsets.…”

The GGOS as the backbone for global observing and local monitoring: A user driven perspective

“…This, in turn, is important information for reservoir modelling. In the example, sea floor turns out to be uplifting by a few mm/year relative to ITRF2000, which is the latest realisation of ITRS (Altamimi et al, 2002). A key question is how much this number is affected by long-term trends in ITRF2000 and its approximation through GPS.…”