ITRF2014: A new release of the International Terrestrial Reference Frame modeling nonlinear station motions

Abstract

For the first time in the International Terrestrial Reference Frame (ITRF) history, the ITRF2014 is generated with an enhanced modeling of nonlinear station motions, including seasonal (annual and semiannual) signals of station positions and postseismic deformation for sites that were subject to major earthquakes. Using the full observation history of the four space geodetic techniques (very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite (DORIS)), the corresponding international services provided reprocessed time series (weekly from SLR and DORIS, daily from GNSS, and 24 h session‐wise from VLBI) of station positions and daily Earth Orientation Parameters. ITRF2014 is demonstrated to be superior to past ITRF releases, as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities. The ITRF2014 long‐term origin coincides with the Earth system center of mass as sensed by SLR observations collected on the two LAGEOS satellites over the time span between 1993.0 and 2015.0. The estimated accuracy of the ITRF2014 origin, as reflected by the level of agreement with the ITRF2008 (both origins are defined by SLR), is at the level of less than 3 mm at epoch 2010.0 and less than 0.2 mm/yr in time evolution. The ITRF2014 scale is defined by the arithmetic average of the implicit scales of SLR and VLBI solutions as obtained by the stacking of their respective time series. The resulting scale and scale rate differences between the two solutions are 1.37 (±0.10) ppb at epoch 2010.0 and 0.02 (±0.02) ppb/yr. While the postseismic deformation models were estimated using GNSS/GPS data, the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques, showing a very high level of consistency which enforces more the link between techniques within the ITRF2014 frame. The users should be aware that the postseismic deformation models are part of the ITRF2014 products, unlike the annual and semiannual signals, which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame.

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

“…These corrections are mainly geophysical ones, such as solid Earth tides and ocean tidal loading (for full details, see the IERS Conventions 2010, Petit and Luzum 2010); the purpose of these corrections is to obtain positions with more regular time variation, which better conform to the linear time-variable coordinate modelling approach used and thus improve the transformation to a certain reference epoch (to obtain a quasi-static state). The most recent realization of the ITRS is the ITRF2014 (Altamimi et al 2016); however, all results in the present paper are based on the previous realization ITRF2008 with the reference epoch 2005.0. The uncertainty (standard deviation) of the geocentric Cartesian coordinates (X, Y, Z ) is at the level of 1 cm or better; for further details, see Petit and Luzum (2010).…”

Application of the Undifferenced GNSS Precise Positioning in Determining Coordinates in National Reference Frames

“…Thus, it is necessary to define the coordinates for a specific epoch, taking into account local velocities and vertical movements (Petit and Luzum, 2010). The actual realization of ITRS is ITRF2008, has been recently replaced by ITRF2014 (Altamimi et al, 2016). To maintain the stability of coordinates in time, the International Association of Geodesy (IAG) sub-commission EUREF adopted the European Terrestrial Reference System (ETRS89) which is consistent with ITRS at the epoch t 0 = 1989.0 and fixed to a stable part of the Eurasian Plate (Bosy, 2013).…”

Geodetic VLBI with an artificial radio source on the Moon: a simulation study

“…Geodetic VLBI is also important for the realization and the maintenance of the International Terrestrial Reference Frame (ITRF; Altamimi et al 2016;Bachmann et al 2016).…”