Horizontal and vertical velocities derived from the IDS contribution to ITRF2014, and comparisons with geophysical models

Abstract

S U M M A R YIn the context of the 2014 realization of the International Terrestrial Reference Frame, the International DORIS (Doppler Orbitography Radiopositioning Integrated by Satellite) Service (IDS) has delivered to the IERS a set of 1140 weekly SINEX files including station coordinates and Earth orientation parameters, covering the time period from 1993.0 to 2015.0. From this set of weekly SINEX files, the IDS combination centre estimated a cumulative DORIS position and velocity solution to obtain mean horizontal and vertical motion of 160 stations at 71 DORIS sites. The main objective of this study is to validate the velocities of the DORIS sites by comparison with external models or time-series. Horizontal velocities are compared with two recent global plate models (GEODVEL 2010 and NNR-MORVEL56). Prior to the comparisons, DORIS horizontal velocities were corrected for Global Isostatic Adjustment from the ICE-6G (VM5a) model. For more than half of the sites, the DORIS horizontal velocities differ from the global plate models by less than 2-3 mm yr −1 . For five of the sites (Arequipa, Dionysos/Gavdos, Manila and Santiago) with horizontal velocity differences with respect to these models larger than 10 mm yr −1 , comparisons with GNSS estimates show the veracity of the DORIS motions. Vertical motions from the DORIS cumulative solution are compared with the vertical velocities derived from the latest GPS cumulative solution over the time span 1995.0-2014.0 from the University of La Rochelle solution at 31 co-located DORIS-GPS sites. These two sets of vertical velocities show a correlation coefficient of 0.83. Vertical differences are larger than 2 mm yr −1 at 23 percent of the sites. At Thule, the disagreement is explained by fine-tuned DORIS discontinuities in line with the mass variations of outlet glaciers. Furthermore, the time evolution of the vertical time-series from the DORIS station in Thule show similar trends to the GRACE equivalent water height.

Stochastic models in the DORIS position time series: estimates for IDS contribution to ITRF2014

“…Also, for a few stations, in the East direction, individual STDs of noise are strictly outlying from the others, as, for example, AREA with an STD equal to 44.1 mm, CACB with an STD equal to 45.7 mm and WALA with an STD equal to 33.2 mm. Station Arequipa was also found by Moreaux et al (2016b) to outlie from others in terms of its horizontal velocity value. The authors emphasised that this may arise from a period of time with no beacon longer than 3 years.…”

“…The position is sampled every seven days and may be used for geodynamical studies (Crétaux et al 1998;Soudarin et al 1999;Moreaux et al 2016b). A proper determination of the long-term trend, which may be due to post-glacial rebound, or geophysical or anthropogenic origin, has to be accompanied by the determination of the seasonalities (Blewitt and Lavallée 2002;Bos et al 2010) and accompanied by a noise analysis to provide the optimal assessment of the trend uncertainty (Williams 2003).…”

“…Among the latest estimations on DORIS velocities, Moreaux et al (2016b) determined the horizontal and vertical velocities from the IDS contribution to ITRF2014 and compared them to two global plate models with an a priori correction for global isostatic adjustment (GIA). They also assessed the errors of the velocity estimates, but assuming only a pure white noise.…”

The Correlations of the Helmert Transformation Parameters as an Additional Auxiliary Diagnostic Tool for Terrestrial Reference Frames Quality Assessment

“…The IDS solutions (Moreaux et al 2016; DORIS cumulative solutions n.d.) are the official DORIS-only TRFs. IDS provide five different TRFs which are aligned to the ITRF2014 solutions.…”

On Satellite-Borne GPS Data Quality and Reduced-Dynamic Precise Orbit Determination of HY-2C: A Case of Orbit Validation with Onboard DORIS Data

“…DORIS is a highly accurate tracking system developed by France, with approximately 60 beacons globally for one-way accurate measurements. DORIS contributes to the International Terrestrial Reference Frame (ITRF), and ITRF2014 benefits from improved analysis strategies of the seven contributing International DORIS Service (IDS) analysis centres [28]. The CNES/CLS analysis centre contributes to the geodetic and geophysical research activity through DORIS data analysis [29].…”