About

The GNSS solution named ’NGL20’ is produced by the Nevada Geodetic Laboratory (NGL) using a Precise Point Positioning (PPP) data analysis strategy. The latest version of GipsyX software and models, orbits and clocks from the Jet Propulsion Laboratory (JPL) have been used to produce daily position time series expressed in the ITRF2020 reference frame (Blewitt et al. 2018). The data set covers the period January 1996 to September 2025.

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 23,000 stations processed by NGL, as many as 1523 have actually been identified as co-located, or nearby, tide gauges, and/or capable of measuring sea leavel through the GNSS-Reflectometry technique.

The GNSS velocities, provided here for 1195 stations (nearby tide gauges and reference frame stations included) with a minimum record length of 3 years and data gaps not exceeding 30%, are produced by NGL using the MIDAS estimator (Blewitt et al. 2016).

More details about the GNSS data analysis strategy can be found here or in Blewitt et al. (2016).