The GFZ Helmholtz Centre for Geosciences (GFZ) acts as an operational analysis center of the EUMETNET EIG GNSS water vapour programme (E-GVAP, https://egvap.dmi.dk/). GFZ provides all types of tropospheric products in near-real time in three processing lines: ultra-rapid (E-GVAP solution ID is GF1U), rapid (GF1R), and global (GF1G). The ultra-rapid solution series is published hourly with a delay of around 15 minutes after the end of each hour.

Operational tropospheric products of GFZ included in this data publication are:
(1) Zenith Total Delays (ZTD), Integrated Water Vapor (IWV);
(2) Tropospheric gradients in North and East directions;
(3) Slant Total Delays (STD)

Based on a network of around 600 GNSS stations of the global tracking network of the International GNSS Service and the Satellitenpositionierungsdienst der deutschen Landesvermessung (SAPOS, Satellite Positioning Service of German state surveying agencies, http://www.sapos.de/), the GFZ Analysis Center generates hourly solutions using the latest development version of the EPOS.P8 Software.

The solution series contains:

(A) Zenith Total Delays (ZTD), Integrated Water Vapor (IWV), tropospheric gradients
Folder sinex_trop_ULTRA_RAPID_EPOS8 with subfolders for GPS weeks (e.g., w2348):
daily files for each processed GNSS site.

Files:
IIIIWWWWD.tro: files with Zenith Total Delays, Integrated Water Vapor, tropospheric Gradients;
IIIIWWWWD.zpd: files with Zenith Total Delays and tropospheric gradients;

where
IIII - GNSS site name,
WWWW - GPS week,
D - day of the week;

Data format: SINEX_TRO: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5030246

(B) Zenith Total Delays (ZTD)
Folder product_COST_ULTRA_RAPID_EPOS8/ with subfolders for each year (e.g., y2024) and month (e.g., m12):
daily files with ZTDs for all processed GNSS sites in one file.

File naming convention: cost_h_o_YYYYMMDDhh:mm_YYYYMMDDhh:mm_mult_gf1u.dat;
cost = total zenith delay in COST format
h = hourly files
o = operational product
YYYYMMDDhh:mm = begin-date-time_end-date-time (year month day hour minute)
mult = multi GNSS constellation
gf1u = GFZ ultra-rapid product version 1
(example file: cost_h_o_202501290900_202501290959_mult_gf1u.dat)

Data format is COST716 ascii format for ground based GNSS data, developed by E-GVAP: https://rom-saf.eumetsat.int/egvap_cost.pdf

(C) Slant Total Delays (STD)
Folder slants_ULTRA_RAPID_EPOS8, subfolders for each year: daily files with Slant Total Delays for all processd GNSS sites in ASCII format:

file naming convention: slant_h_o_YYYYMMDDhh:mm_YYYYMMDDhh:mm_mult_gf1u.dat with
slant = slant total delay product
h = hourly files
o = operational product
YYYYMMDDhh:mm = begin-date-time_end-date-time (year month day hour minute)
mult = multi GNSS constellation
gf1u = GFZ ultra-rapid product version 1
(example fie: slant_h_o_202501291400_202501291459_mult_gf1u.dat.gz)

The processing is done with GFZ EPOS.P8 Software. It follows the current geodetic conventions (https://www.iers.org/SharedDocs/Publikationen/EN/IERS/Publications/tn/TechnNote36/tn36.pdf) and GFZ IGS Analysis Center Notes (https://files.igs.org/pub/center/analysis/gfz.acn). The processing strategy is described in https://www.gruan.org/documentation/gruan/td/gruan-td-6