GNSS Final Troposphere Zenith Path Delay Combination Product

doi: 10.5067/gnss/gnss_igstropzpd_001

Data Center Citation

Noll, Carey E., The Crustal Dynamics Data Information System: A resource to support scientific analysis using space geodesy, Advances in Space Research, Volume 45, Issue 12, 15 June 2010, Pages 1421-1440, ISSN 0273-1177,

Data Citation

International GNSS Service, GNSS Final Troposphere Zenith Path Delay Combination Product, Greenbelt, MD, USA: NASA Crustal Dynamics Data Information System (CDDIS), Accessed [[enter user data access date]] at doi:10.5067/GNSS/gnss_igstropzpd_001.

Other standard citation formats may be used for this data set and can be found at the DOI Citation Formatter website.

More information about CDDIS data citations and acknowledgments is available.


  • Name: GNSS Final Troposphere Zenith Path Delay Combination Product
  • Format: IGS Format
  • Spatial Coverage: 90.0 to -90.0, 180.0 to -180.0
  • Temporal Coverage: 2000-10-22 to present
  • Temporal Resolution: 300 second sampling interval
  • File Size: 10 Kb
  • Platforms: GNSS satellites (e.g., GPS)


This derived product set consists of Global Navigation Satellite System Final Combined Station Positions/Velocities Summary Product available from the Crustal Dynamics Data Information System (CDDIS). GNSS satellites provide autonomous geo-spatial positioning with global coverage. GNSS data sets from ground receivers at the CDDIS consist primarily of the data from the U.S. Global Positioning System (GPS) and the Russian GLObal NAvigation Satellite System (GLONASS). Since 2011, the CDDIS GNSS archive includes data from other GNSS (Europe’s Galileo, China’s Beidou, Japan’s Quasi-Zenith Satellite System/QZSS, the Indian Regional Navigation Satellite System/IRNSS, and worldwide Satellite Based Augmentation Systems/SBASs), which are similar to the U.S. GPS in terms of the satellite constellation, orbits, and signal structure. Analysis Centers (ACs) of the International GNSS Service (IGS) retrieve GNSS data on regular schedules to produce precise orbits identifying the position and velocity of the GNSS satellites as well as precise station positions and velocities for the network of GNSS receivers. The IGS Reference Frame Coordinator uses these individual AC solutions to generate the official IGS station position/velocity product. The final products are considered the most consistent and highest quality IGS solutions and consists of daily and weekly station position and velocity files in SINEX format, generated on a daily/weekly basis by combining solutions from individual IGS ACs, approximately 11-17 days after the end of the solution week.

IGS associate analysis centers generate troposphere products from ground-based GNSS data. These products include five-minute estimates of zenith path delay (ZPD) and north and east troposphere gradient components. Data are available in daily files by site for over 350 GNSS stations in the IGS network. Measurements of surface pressure and temperature at GNSS sites allow the extraction of precipitable water vapor from the total zenith path delay. Final troposphere estimates for over 350 stations in the IGS network. The troposphere products utilize the IGS final satellite, orbit, and EOP products and are therefore available approximately three weeks following the observation day. Troposphere products are available in a standard, IGS format.

Since the inception of the troposphere product, three analysis groups (GFZ, JPL, and currently USNO) have generated the IGS combination solution each using different methodologies. Therefore, the resulting file types have changed through the years. The current product consists of files containing daily ZPD estimates for selected sites in the IGS network. The original product consisted of one file per site per GPS week.

Data Access

The GNSS Final Troposphere Zenith Path Delay Combination Products are online:

in subdirectories by year and day of year as follows:


Code Meaning
YYYY 4-digit year
DDD3-digit day of year
SSSS 4-character monument code
#file number for the day, typically 0
YY2-digit year
.gz gzip compressed file