The CDDIS provides an archive of GNSS data in support of the International GNSS Service (IGS, www.igs.org). We have data in daily files (30 second sampling) going back to 1992, hourly files (30-second sampling), and high-rate files (1-second sampling). The daily data are typically delivered to the CDDIS within 1-6 hours after the end of the UTC day; the hourly data within 5 to 20 minutes after the start of the hour. The operational archive of GNSS data consists of the U.S. GPS (Global Positioning System) and Russian GLONASS (GLObal NAvigation Satellite System) systems. In support of the IGS Multi-GNSS Experiment (MGEX), the CDDIS provides access to other GNSS such as Galileo (operated by the European Space Agency, or ESA), Japan’s QZSS (Quasi-Zenith Satellite System), China’s Beidou (BeiDou Navigation Satellite System, or BDS), and Indian Regional Navigation Satellite System (IRNSS) systems.
How can I access the GNSS data?
The GNSS data are freely available for download through https and other methods.
The data are stored in subdirectories by type (daily, hourly, high-rate), by year, and by day of year.
Access the GNSS data by using one of the following methods:
- via https at URL https://cddis.nasa.gov/archive/gnss/data/
- via ftp-ssl using the command line and ftps://gdc.cddis.gsfc.nasa.gov/gnss/data/
What is the RINEX format for GNSS data?
The "Receiver Independent Exchange Format" RINEX format was first developed by the Astronomical Institute of the University of Berne for the easy exchange of the GPS data to be collected during GPS campaigns. The format consists of six ASCII file types, observation, navigation, meteorological, GLONASS navigation, GEO navigation, and satellite and receiver clock files. Each file type consists of a header section and a data section. CDDIS currently archives data in RINEX V2, RINEX V3, and RINEX V4 formats. The format documentation is available at https://igs.org/formats-and-standards/.
How are the daily GNSS data files stored?
GNSS data are available in daily subdirectories of the form /gnss/data/daily/yyyy/ddd, where yyyy is the four-digit year and ddd is the three-digit day of year. All data are stored in the RINEX V2, RINEX V3, or RINEX V4 formats. The format documentation is available at https://igs.org/formats-and-standards/.
How can I access hourly GNSS data files?
Hourly GNSS data files are available through encrypted ftp and other methods.
Access the hourly GNSS data by using one of the following methods:
- via https at URL https://cddis.nasa.gov/archive/gnss/data/hourly/
- via ftp-ssl using the command line and ftps://gdc.cddis.eosdis.nasa.gov
How are the hourly GNSS data files stored?
Hourly GNSS data files are available in hourly subdirectories within the file system https://cddis.nasa.gov/archive/gnss/data/hourly/ YYYY/DDD/HH, where YYYY is the four-digit year, DDD is the three-digit day of year, and HH is the numeric hour of the day (00, 01, ... 23). All data are stored in RINEX V2, RINEX V3, or RINEX V4 formats. The format documentation is available at https://igs.org/formats-and-standards/.
How can I access high-rate GNSS data files?
High-rate GNSS data files are available through encrypted ftp and other methods. These high-rate GNSS data are available since May 2001.
Access the high-rate GNSS data by using one of the following methods:
- via https at URL https://cddis.nasa.gov/archive/gnss/data/highrate/
- via ftp-ssl using the command line and gdc.cddis.eosdis.nasa.gov
How are the high-rate GNSS data files stored?
High-rate GNSS data files are available in hourly subdirectories within the file system /archive/gnss/data/highrate//YYYY/DDD/YYt/HH, where YYYY is the four-digit year, DDDD is the three-digit day of year, YY is the two-digit year, t is the file type, and HH is the numeric hour of the day (00, 01, ... 23). High-rate data are stored in files containing fifteen minutes of data. All data are stored in the RINEX V2, RINEX V3, and RINEX V4 formats. The format documentation is available at https://igs.org/formats-and-standards/.
What type of GNSS products are available from the CDDIS?
Products derived from GNSS data and available from the CDDIS are provided by analysis centers supporting the International GNSS Service (IGS). 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 products.
How can I access products derived from GNSS data?
GNSS products are available through encrypted ftp and other methods. GNSS products (precise ephemerides) since June 1992 are available online.
Access the GNSS products by using one of the following methods:
- via https at URL https://cddis.nasa.gov/archive/gnss/products/
- via ftp-ssl using the command line and ftps://gdc.cddis.eosdis.nasa.gov
How accurate are the GNSS products produced by the IGS?
The IGS Central Bureau maintains a table of accuracy information for the official IGS products. Additional information is available from a web page maintained by the Analysis Center Coordinator (ACC).
How can I find out what data are archived?
Users can view CDDIS daily status files, found in the daily GNSS data directories, which detail data availability for a particular day.
How can I obtain data not currently online?
Access to GNSS data not accessible through encrypted ftp or https can be requested by contacting the CDDIS manager.
How can I find out more about IGS stations?
The IGS tracking network web page provides a list of current IGS sites and links to their site logs; a map is also available.
What is the BRDC navigation file?
The file https://cddis.gsfc.nasa.gov/archive/gnss/data/daily/ brdcddd0.yyn.gz (yy is the two-digit year, ddd is the three-digit day of year) is the daily broadcast ephemeris file. This file is a merge of the individual site navigation files into one, non-redundant file that can be utilized by users instead of the many individual navigation files. These files are also available in yearly subdirectories of https://cddis.gsfc.nasa.gov/archive/gnss/data/daily/yyyy/brdc.
What is the HOUR navigation file?
The file https://cddis.gsfc.nasa.gov/archive/gnss/data/hourly/hourddd0.yyn.gz (yy is the two-digit year, ddd is the three-digit day of year) is a combined broadcast ephemeris file. This file is generated on an hourly basis from all hourly navigation files archived at the CDDIS. The hourly navigation file contains all broadcast messages with the TOE of the day ddd that are available when the file is created at the top of the hour. The file is updated each hour with new navigation messages. At the end of the UTC day, when the final version of the file is generated, the file is copied to the https://cddis.nasa.gov/archive/gnss/data/daily/[b]yyyy[/b]/ddd/yyn/ and https://cddis.nasa.gov/archive/gnss/data/daily/[b]yyyy[/b]/ddd/brdc/ directories and becomes the "daily" broadcast ephemeris file (denoted as brdcddd0.yyn.gz) and described above.
What are the data types in the GNSS daily subdirectories?
Each daily subdirectory under https://cddis.nasa.gov/archive/gnss/data/daily/[b]yyyy[/b]/ddd/ contains twelve subdirectories (yy denotes the two-digit year): yyd (compressed, Hatanaka-compacted RINEX observation data), yyf (Beidou broadcast ephemeris data), yyg (GLONASS broadcast ephemeris data), yyh (SBAS broadcast ephemeris data), yyi (IRNSS broadcast ephemeris data), yyl (Galileo broadcast ephemeris data), yym (RINEX meteorological data for a subset of sites), yyn (GPS broadcast ephemeris data), yyo (compressed RINEX observation data), yyp (Mixed broadcast ephemeris data), yyq (QZSS broadcast ephemeris), and yys (summary files of the observation data) generated by UNAVCO's TEQC software).
How can I use the yyd GNSS data type?
The RINEX observation data have been "compacted" using software developed by Yuki Hatanaka/GSI and then compressed using gzip compression. By using the Hatanka software, the RINEX observation files have been reduced in size by a factor of 2.5. Users must first use the gunzip command, then run the crx2rnx software to un-compact the uncompressed file; the resulting file is a GNSS observation file in RINEX format.
Where can I find out more about GNSS/GPS data?
An overview about GPS can be found at The Global Positioning System. Other links about GPS data can be found in the Links section of the CDDIS web site.
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