IGS Data

The GNSS data consist of the receiver’s observation data, the broadcast orbit information of the tracked satellites, and supporting data, such as meteorological parameters, collected from co-located instruments. Currently, the IGS network consists of over 500 globally distributed stations, equipped with geodetic-quality receivers that track the GPS satellite constellation; a subset of this network are capable of tracking both GPS and GLONASS satellite signals. Furthermore, some stations are upgraded with multi-GNSS receivers capable of obtaining signals from GPS, GLONASS, Galileo and other GNSS (BeiDou, QZS, etc.). These data are available through the CDDIS portal.

The CDDIS archive contains GNSS data from the global network of permanent GNSS receivers supporting the IGS operating at a 30-second sampling rate and containing 24 hours of data (00:00-23:59 UTC). IGS analysis centers retrieve these data daily to produce IGS products. These products, such as the daily and weekly satellite ephemerides, station positions and velocities, satellite and station clock information, and the Earth rotation parameters, are in turn, submitted to the CDDIS.

 

IGS regional data collection centers forward their data holdings of these daily, 30-second GNSS data in compressed RINEX format to the CDDIS on a daily basis. At the present time, an average of nearly 500 sites are archived in this fashion each day for availability to the global science community. In general, a majority of the data delivered to and archived in the CDDIS are available to the user community within a few minutes (to a few hours) after the end of the observation day.

 

Daily GNSS data available in RINEX V2 format use the mmmmDDD#.YYt.Z filename convention and are in UNIX compressed format. Starting with data from 2016, all daily GNSS data in RINEX V3 format that use the RINEX V3 filenaming convention and the gzip compression format are archived with data in RINEX V2 format, in subdirectories in the /gnss/data/daily area.

 

For RINEX V2 data, the CDDIS utilizes UNAVCO‘s TEQC (Translation, Editing and Quality Checking) software on incoming daily 30-second files for quality checking purposes. Metadata are extracted from the TEQC output and stored in the CDDIS database. Data quality information is also maintained in daily “status” files that reflect the timeliness of the data delivered as well as statistics on number of data points, cycle slips, and multipath. Users can thus obtain a snapshot of data availability and quality by viewing the contents of these summary files. Valid data are then archived on-line in daily subdirectories by year, day, and file type within the file system.

 

The CDDIS provides a report that summarizes the contents of a day’s GNSS data holdings. These “status files” reflect timeliness of the data delivered as well as statistics, extracted from the TEQC summaries, on number of data points, cycle slips, and multipath. The user can receive a snapshot of data availability and quality by viewing the contents of such a summary file.

 

RINEX V2 and RINEX V3 files are archived in the same directories.

 

The starting directories for the files are:

Anonymous ftp service will be discontinued on October 31, 2020.

 

Append the following directory and file names to the starting directory using the format codes in the links below:

YYYY/DDD/YYt/mmmmDDD#.YYt.Z

 

YYYY/DDD/YYt/XXXXMRCCC_K_YYYYDDDHHMM_01D_30S_tt.FFF.gz



 

IGS analysis centers retrieve hourly data files to produce IGS “rapid” and “ultra-rapid” products such as satellite ephemerides, clocks, and Earth rotation parameters. The IGS Analysis Center Coordinator generates a daily, combined, rapid product with a 17-hour latency. The ultra-rapid (predicted) orbit and clock products are generated four times per day. These datasets are available through CDDIS.

 

IGS stations forward hourly 30-second GNSS data in compressed RINEX format to the CDDIS within minutes following the end of the hour. At the present time, an average of 350 sites are archived in this fashion each day for availability to the global science community. Hourly GNSS data available in RINEX V2 format use the mmmmDDDH.YYt.Z filename convention and are in UNIX compressed format. Starting with data from 2016, all hourly GNSS data in RINEX V3 that use the RINEX V3 filenaming convention and the gzip compression format are archived with data in RINEX V2 format, in subdirectories in the /gnss/data/hourly area.

 

At the close of the UTC data, the station operators incorporate individual hourly GNSS data into a full day’s data file, submitted to the CDDIS and made available in the daily GNSS data directories. These hourly files are stored in hourly subdirectories within the file system.

 

The starting directory for these files is:

ftp://cddis.nasa.gov/gnss/data/hourly/

Append the following directory and file names tot he starting directory using the format codes in the links below:

YYYY/DDD/HH/mmmmDDDH.YYt.Z

YYYY/DDD/HH/XXXXMRCCC_K_YYYYDDDHHMM_01H_30S_tt.FFF.gz

 

The CDDIS archive contains GNSS data from the global network of permanent GNSS receivers operating at a higher, 1-second sampling rate. These data are submitted and archived in files containing 15 minutes of data. IGS analysis centers retrieve these sub-hourly data files to produce IGS near real-time and “ultra-rapid” products such as satellite ephemerides, clocks, and Earth rotation parameters.

 

IGS stations forward the sub-hourly 1-second GNSS data in compressed RINEX format to the CDDIS within minutes following the end of the 15-minute time block. At the present time, sub-daily data from an average of 160-170 high-rate sites are archived each day. Many of the sites are real-time, streaming sites whose data are captured and translated into blocks of 15-minutes of RINEX data. High-rate GNSS data available in RINEX V2 format use the mmmmDDDHMM.YYt.Z filename convention and are in UNIX compressed format. Starting with data from 2016, all high-rate GNSS data in RINEX V3 that use the RINEX V3 filenaming convention and the gzip compression format are archived with data in RINEX V2 format, in subdirectories in the /gnss/data/highrate area.

 

The starting directory for these sub-hourly, high-rate files is:

ftp://cddis.nasa.gov/gnss/data/highrate/

Append the following directory and file names to the starting directory using the format codes in the links below::

YYYY/DDD/YYt/HH/mmmmDDDHMM.YYt.Z

RINEX V2 format
View format codes

YYYY/DDD/YYt/HH/XXXXMRCCC_K_YYYYDDDHHMM_15M_01S_tt.FFF.gz

RINEX V3 format
View format codes

A large percentage of the GNSS sites provide broadcast navigation data in addition to observation data. The CDDIS creates daily broadcast ephemeris files from these site-specific files transmitted by the stations; these files (one for GPS, a second for GLONASS) contain the unique GPS or GLONASS satellite ephemeris messages for each day. A similar file is created at the start of the UTC day and updated on an hourly basis from the hourly broadcast navigation files. Users can therefore download a single file each day or hour, which contains all broadcast ephemeris messages required for post-processing.

Daily GPS Broadcast Ephemeris Files

The daily GPS broadcast ephemeris 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.

The daily file created at BKG each day contains unique navigation messages from sites in Europe.

The starting directory for the daily files is:

Anonymous ftp service will be discontinued on October 31, 2020.

Append the following directory and file names to the starting directory:

YYYY/DDD/YYn/brdcDDD0.YYn.Z   (merged GPS broadcast ephemeris file)

OR

YYYY/brdc/brdcDDD0.YYn.Z   (merged GPS broadcast ephemeris file)

YYYY/DDD/YYn/ifagDDD0.YYn.Z   (daily file historically created at BKG)

as described in the table at the bottom of the page.

Hourly GPS Broadcast Ephemeris Files

The combined broadcast ephemeris 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 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 daily directories and becomes the “daily” broadcast ephemeris file

The starting directory for the hourly files is

Anonymous ftp service will be discontinued on October 31, 2020.

Append the following directory and file names to the starting directory:

YYYY/DDD/hourDDDm.YYn.Z

as described in the table at the bottom of the page.

Daily GLONASS Broadcast Ephemeris Files

Similarly, the daily GLONASS-only broadcast ephemeris file can be found in the GLONASS navigation file subdirectory.

The starting directory for thedaily GLONASS-only files is

ftp://cddis.nasa.gov/gnss/data/daily/.

Append the following directory and file names to the starting directory:

YYYY/DDD/YYg/brdcDDD0.YYg.Z

OR

YYYY/brdc/brdcDDD0.YYg.Z

The following codes are used in the paths and file names for the data:

Code Meaning
YYYY 4-digit year
YY 2-digit year
DDD 3-digit day of year
.Z compressed Unix file

RINEX Version 2 is the format used by the IGS for operational data holdings. However, data support for additional GNSS, such as Galileo, QZS, and BeiDou, uses an enhanced version of RINEX available in Version 3. The CDDIS provides an archive of data from these additional GNSS through the IGS Multi-GNSS Experiment (MGEX).

 

The IGS established MGEX to track, collate and analyze all available GNSS signals, including Galileo, QZSS, and BeiDou, as well as modernized GPS and GLONASS satellites and any space-based augmentation system (SBAS) of interest. Analysis centers will attempt to estimate inter-system calibration biases, compare equipment performance and further develop processing software capable of handling multiple GNSS observation data.

 

The CDDIS is one of three IGS data centers supporting the IGS MGEX, expanding its data archive and distribution service to include data from participating multi-GNSS receivers, products derived from the analysis of these data, and any required metadata for the experiment. The archive now contains daily and hourly 30-second and sub-hourly 1-second data from an additional 100+ stations in RINEX V3 format. The CDDIS developed software to extract metadata from the RINEX headers for use in reporting and archive management. The software is also used to generate daily status files summarizing data holdings similar to those provided in the CDDIS IGS operational directories. However, data quality information, as produced by TEQC, is not available through this software.

 

The MGEX data are available within the campaign subdirectory structure in the CDDIS archive. These data are currently provided in RINEX V3 format.

The starting directory for these files is:

ftp://cddis.nasa.gov/gnss/data/campaign/mgex/

Append the following directory and file names to the starting directory:

daily/rinex3/YYYY/DDD/YYt/  (daily 30-second files)

hourly/rinex3/YYYY/DDD/HH/  (hourly 30-second files)

highrate/rinex3/YYYY/DDD/HH/YYt/  (15-minute 1-second files)

as described in the table below.

Code Meaning
YYYY 4-digit year
DDD 3-digit day of year
YY 2-digit year
HH 2-digit hour
t

type of data:

d = Hatanaka-compressed observation data
e =
f = Compass/Beidou broadcast ephemeris
g = GLONASS navigation message data
h = SBAS payload navigation message data
l = GLONASS navigation message data
m = meteorological data
n = GPS navigation message data
o = observation data
p = mixed GNSS navigation message data
q = QZSS navigation message data
s = observation summary files (extracted from RINEX header)

.Z UNIX compressed file

 

Append the file names using the codes below:

mmmmDDD#.YYt.Z

Code Meaning
mmmm 4-character site monument name
DDD 3-digit day of year
# sequence number (0, 1, …) indicating multiple files within a day; typically 0
YY 2-digit year
t

type of data:

d = Hatanaka-compressed observation data (doi:10.5067/GNSS/gnss_daily_d_001)
g = GLONASS broadcast ephemeris data (doi:10.5067/GNSS/gnss_daily_g_001)
m = meteorological data (doi:10.5067/GNSS/gnss_daily_m_001)
n = GPS broadcast ephemeris data (doi:10.5067/GNSS/gnss_daily_n_001)
o = observation data (doi:10.5067/GNSS/gnss_daily_o_001)
s = observation summary files (output of TEQC) (doi:10.5067/GNSS/gnss_daily_s_001)

.Z UNIX compressed file
The CDDIS has configured dedicated servers for receipt and transmission of real-time GNSS data and product streams in support of the IGS Real Time Service. The CDDIS has installed and tested the required real-time streaming software (NTRIP, Networked Transport of RTCM via Internet Protocol). The available product streams consist of GNSS orbit and clock corrections, which enable varied applications such as precise point positioning (PPP). In the near term, the CDDIS plans to continue testing and coordination with the RTS. Future plans include capturing incoming data streams for generation of high-rate data files from real-time stations.

More information and registration details on the real-time GNSS streams available from the CDDIS can be viewed on the CDDIS Caster Description webpage.