DOI: 10.5880/gfz.irzr.2025.003
title: GFZ GNSS-derived tropospheric data products (global)

description: 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 global solution series is published hourly with a delay of around 50 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)
description: 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_GLOBAL_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_GLOBAL_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_gf1g.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 
gf1g = GFZ global product version 1 
(example file: cost_h_o_202501290900_202501290959_mult_gf1g.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_GLOBAL_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_gf1g.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 
gf1g = GFZ global product version 1 
(example fie: slant_h_o_202501291400_202501291459_mult_gf1g.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