Heligoland GNSS hourly time series positioning for 2017-2021

This dataset includes 1-hour GNSS coordinate product processed by GFZ. The observations are from the two GNSS station installed by BKG on the small offshore island of Heligoland in the North Sea. These products are hourly position time series (North, East and Vertical). The 30-second daily RINEX files since 2020 are downloaded from BKG. Together with 5 IGS stations in Europe, the collected RINEX data are processed with the Earth Parameter and Orbit System (EPOS) software from GFZ. The EPOS software uses un-difference carrier phase and pseudo-range observables from GPS and GLONASS L1 and L2 frequencies. They formed an ionosphere-free linear combination to remove the first-order ionosphere effect in the observation. The phase center variation (PCV/PCO) of the satellite and ground station antenna are corrected by IGb14. The station deformation caused by ocean tide loading is modeled by the FES2004 model. Apriori zenith hydro-static/non-hydro-static delay is obtained using the Global Pressure and Temperature model (GPT2) and Vienna mapping functions (VMF) in a 6-hour grid file database. To ensure consistency in the GNSS data analysis, we took the GNSS precise satellite orbits as well as clock products from the 2nd reprocessed (before 2014) and routine (since 2015) yield by EPOS software. The same station parameters are set up as used for the GNSS orbit and clock estimation. All the GNSS data were processed in units of 24 hours periods. The estimated parameters are (i) the receiver clock error for every epoch as white noise, (ii) the hourly station coordinates, (iii) daily tropospheric gradients, (iv) the daily inter-system clock bias for GLONASS, and (v) 2-hour tropospheric wet zenith delays with random-walk constrain.