GNSS Daily Ionosphere Total Electron Content Grid Fluctuation Product

doi: 10.5067/GNSS/gnss_igsionofluxtec_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 Daily Ionosphere Total Electron Content Grid Fluctuation Product, Greenbelt, MD, USA: NASA Crustal Dynamics Data Information System (CDDIS), Accessed [[enter user data access date]] at doi:10.5067/GNSS/gnss_igsionofluxtec_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 Daily Ionosphere Total Electron Content Grid Fluctuation Product
  • Format: IONEX
  • Spatial Coverage: 90.0 to -90.0, 180.0 to -180.0
  • Temporal Coverage: 1998-01-01 to present
  • Temporal Resolution: Daily
  • File Size: 50 kb
  • Platforms: GNSS (e.g., GPS)


Information on the ionosphere's behavior is of great importance for radio signal propagation applications, and scientists will benefit from up-to-date and long-term ionosphere information. The main ionospheric information provided by GNSS is the electron content, which can be derived from dual-frequency observations, which are available on a global scale from the stations in the IGS network. VTEC maps can provide useful information for monitoring the effects of space weather and improvements in navigation applications.

This derived product set consists of Global Navigation Satellite System a Ionosphere Vertical Total Electron Content (VTEC) fluctuation measurement product (daily files) from the NASA 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. GNSS observations from a global network can be utilized for atmospheric measurements. Analysis Centers (ACs) of the International GNSS Service (IGS) retrieve GNSS data on regular schedules to produce independently computed VTEC maps. These fluctuations in TEC consists of a rate of TEC change index (ROTI) maps which are constructed with the grid of 2 degrees by 2 degrees resolution as a function of the magnetic local time and corrected magnetic latitude. GNSS data are used to determine ROTI maps, the standard deviation of rate of TEC change over a specified time span; ROTI can be used to describe irregularities in the ionosphere.

Data Access

The GNSS Daily Ionosphere Total Electron Content Grid Fluctuation Products are online:

in subdirectories by year, day of year, and data type as follows:



Code Meaning
YYYY4-digit year
DDD 3-digit day of year
YY2-digit year
# sequence number (0, 1, ...) indicating multiple files within a day; typically 0
.Z UNIX compressed file