US Government security requirements no longer permit CDDIS to offer data via traditional unencrypted anonymous ftp; this service was discontinued on October 31, 2020. All data are still available, however access must be via HTTPS or ftp-ssl.

Instructions with examples and our FAQ can be found at: https://cddis.nasa.gov/Data_and_Derived_Products/CDDIS_Archive_Access.html.

If you still have difficulty after reading and attempting the examples on that page, please contact us at support-cddis@earthdata.nasa.gov.

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GNSS product holdings

Products derived from GNSS data archived in the CDDIS are generated and submitted by the IGS analysis and associate analysis centers. IGS products support scientific research in:

  • Realization of the International Terrestrial Reference Frame (ITRF)
  • Monitoring deformation of the solid Earth
  • Monitoring Earth rotation
  • Monitoring variations in the hydrosphere (sea level, ice sheets, etc.)
  • Scientific satellite orbit determination
  • Monitoring the Earth’s ionosphere and troposphere
  • Time and frequency transfer

IGS operational products include precise GNSS satellite ephemerides, positions and velocities of stations in the global GNSS network, EOPs (polar motion and rates, length-of-day), and station and satellite clock solutions. Other products derived from the CDDIS GNSS data holdings include troposphere Zenith Path Delay (ZPD) estimates (both dry and wet components) and global ionosphere maps, in support of IGS Working Groups or Pilot Projects.

Spatial coverage

Temporal coverage

  • GNSS orbit, station position, and EOP products since June 1992
  • Troposphere Zenith Path Delay (ZPD) products since January 1997
  • Ionosphere Total Electron Content (TEC) products since June 1998

Data volume

  • Weekly and daily GNSS orbits, station position, and EOP files: ~1.5 Gbytes/week (compressed)
  • Daily troposphere files: ~3 Mbytes/day (compressed)
  • Daily ionosphere files: ~5 Mbytes/day (compressed)

Data formats

Related resources