The GNSS solution named ’NGL08’ was produced by the Nevada Geodetic Laboratory (NGL) using a Precise Point Positioning (PPP) data analysis strategy. The GIPSY/OASIS-II software (version 6.1.1) from the Jet Propulsion Laboratory (JPL) was employed to produce daily position time series for over 17,000 globally distributed stations using JPL satellite orbits and clock products expressed in the IGS08 reference frame (Blewitt et al. 2018). The data set covers the period January 1996 to May 2018.
This GNSS data analysis strategy complies with the standards (models, corrections,...) of the International GNSS Service (IGS) reanalysis (reprocessing) campaigns ; hence the Sixteenth session of the Group of Experts for the Global Sea Level Observing System (GLOSS), held in Busan (Republic of Korea), 11-13 April 2019, tasked the SONEL data assembly centre to consider including the NGL solution (position time series and velocities) for the subset of GNSS stations nearby tide gauges. Among the more than 17,000 stations processed by NGL, as many as 989 were indeed identified as co-located, or nearby, tide gauges.
The GNSS velocities, provided here for 818 stations with a minimum record length of 3 years and data gaps not exceeding 30%, were produced by NGL using the MIDAS estimator (Blewitt et al. 2016).