Products

IGS analysis centers provide clock solutions to the CDDIS using pre-determined schedules, e.g., daily and weekly. The IGS analysis center coordinator retrieves these solutions and produces a combined product, which is then in turn archived at the CDDIS. The IGS produces clock results in two forms, tabulate at 5 minutes and 30 seconds. These combination solutions are considered the official IGS products.

IGS clock combination solutions are available in two forms: rapid and final. The rapid clock combination is a daily solution available approximately 17 hours after the end of the previous UTC day. The final, and most consistent and highest quality IGS solutions, consists of daily clock files, generated on a weekly basis approximately 13 days after the end of the solution week. All clock solution files utilize the RINEX Extensions to Handle Clock Information.

All operational IGS GNSS products (i.e., orbits, station positions, EOP, clock solutions) are available in subdirectories by GPS week. Solution summary files are provided by the analysis centers in which they describe their analysis methods and strategies and list processing statistics. Descriptions of AC analysis procedures and models used are available from the IGS website.

In 2009 and 2013, the IGS initiated “reprocessing campaigns” (repro1 and repro2 respectively). The IGS analysis centers re-processed the GNSS data from the global network of IGS stations (from 1994 to 2007 for repro1, from 1994 through 2012/2013 for repro2) to produce a fully consistent set of products utilizing the most recent models and updated processing strategies. These reprocessed solutions are available within the weekly subdirectory structure as outlined below, in /repro1 and /repro2 subdirectories.

The starting directory for these files (GPS and GPS+GLONASS solutions) is:

https://cddis.nasa.gov/archive/gnss/products

and for GLONASS-only solutions:

https://cddis.nasa.gov/archive/gnss/glonass

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

WWWW/AAAWWWWD.TYP.Z

as described in the table below.

Though many clock products are available, the products listed below have permanent DOIs:

as described in the table below.

The IGS combined, final station position solutions (GNSS only) are available on a weekly basis.

The starting directory for these files is:

https://cddis.nasa.gov/archive/gnss/products/   (GPS and GPS+GLONASS solutions)

Append the following directory and file names to the starting directory as described in the table below the list.

Since 1998, IGS associate analysis centers have provided products containing ionosphere vertical total electron content (TEC) maps and daily GNSS satellite differential code bias (DCB) values derived from the dual-frequency GNSS data. Daily ionospheric fluctuation maps are also available. The IGS product is derived from analysis center solutions, both rapid and final. These ionosphere products are available in a rapid solutions with a latency of less than 24 hours, a final solution with a latency of approximately 11 days, and a predicted solution, available both one and two days prior. Ionosphere products are provided in IONEX (ionosphere exchange) format.

The starting directory for the current ionospheric solution files is:

https://cddis.nasa.gov/archive/gnss/products/ionex/

Append the following directory and file names to the starting directory for current files:

YYYY/DDD/AAAgDDD#.YYi.Z

Vertical total electron content (TEC) maps

YYYY/DDD/rotiDDD0.YYf.Z

Daily ROTI (rate of TEC index) product

as described in the table below.

The IGS analysis centers re-processed the historical IGS data set (from 1994 to 2007 for repro1, from 1994 through 2012/2013 for repro2) to produce a fully consistent set of products utilizing the most recent models and updated processing strategies.

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.

Historical tropospheric products are also available. These products are no longer updated.

The starting directory for the current troposphere solution files is:

https://cddis.nasa.gov/archive/gnss/products/troposphere/zpd/

Append the following directory and file names to the starting directory for current files:

TYP/SSSSDDD#.YYzpd.gz

as described in the table below.

The starting directories for the historical troposphere product files are:

Differential Code Biases (DCBs) are the systematic errors, or biases, between two GNSS code observations at the same or different frequencies. DCBs are required for code-based positioning of GNSS receivers, extracting ionosphere total electron content (TEC), and other applications. Proper knowledge of DCBs is crucial to many navigation applications but also non-navigation applications such as ionospheric analysis and time transfer. With all of the new signals offered by modernized and new GNSS constellations, analysts now require a comprehensive multi-GNSS DCB product.

As part of the IGS Multi-GNSS Experiment (MGEX) two different DCB products are determined by two analysis groups: Institute of Geodesy and Geophysics (IGG) of the Chinese Academy of Sciences (CAS) in Wuhan and the Deutsche Forschungsanstalt für Luftund Raumfahrt (DLR) in Germany. These files are archived at the CDDIS:

https://cddis.nasa.gov/archive/gnss/products/bias/

The satellite and station biases computed by the Institute of Geodesy and Geophysics (IGG) of the Chinese Academy of Sciences (CAS) in Wuhan are generated on a daily basis with a latency of 2-3 days and made available in daily BSX files. The constellations and signals analyzed by the IGG CAS are:

Reference: Wang N., Yuan Y., Li Z., Montenbruck O., Tan B. (2016) Determination of differential code biases with multi-GNSS observations, Journal of Geodesy, Vol. 90, No. 3, pp. 209-228, DOI 10.1007/s00190-015-0867-4

The DLR product is updated on a 3-monthly basis and comprises weekly averages of the satellite biases. In addition a full set of daily satellite and station biases is provided for reference purposes and trend analyses. The constellations and signals analyzed by the DLR are:

Reference: Montenbruck O., Hauschild A., Steigenberger P. (2014), Differential Code Bias Estimation using Multi-GNSS Observations and Global Ionosphere Maps, Navigation – Journal of the ION, Vol. 61, No. 3, pp. 191-201, DOI 10.1002/navi.64

Data Format

The CAS DCBs are provided in a preliminary version of the Bias SINEX (BSX) format whereas DLR used the Version 1.00 of February 2016 until Q4/2016 and the Version 1.00 of December 2016 starting with Q1/2017. The December 2016 version of the Bias SINEX format uses a 4-digit year number whereas the version of February 2016 uses a 2-digit year number for specifying the validity intervals.

Bias SINEX 0.01
http://www.biasws2012.unibe.ch/docs/sinex_bias_0.01-2.txt

Bias SINEX 1.00 (February 2016)
http://www.aiub.unibe.ch/download/bcwg/format/draft/sinex_bias_100_feb07.pdf

Bias SINEX 1.00 (December 2016)
http://www.aiub.unibe.ch/download/bcwg/format/draft/sinex_bias_100_dec07.pdf

File Naming

The DCB file names

CAS0MGXRAP_YYYYDDD0000_01D_01D_DCB.BSX.gz
DLR0MGXFIN_YYYY0010000_NNU_07D_DCB.BSX.gz
DLR0MGXFIN_YYYY0010000_NNU_01D_DCB.BSX.gz

are based on a new naming scheme proposed for future MGEX products, which is inherited from the new RINEX3 file naming convention; the full specification is given as

AAAVPPPTTT_YYYYDDDHHMM_LEN_SMP_CNT.FMT[.?*]

where:

The CDDIS provides access to products generated from real-time data streams in support of the IGS Real-Time Service. Two types of products are archived, igt and igc.

The igt solution is a batch combination based on daily clock and sp3 submissions by IGS real-time analysis center. These clock products have been provided since February 2009, shortly after real-time streams were routinely available through the IGS Real-Time Pilot Project and prior to the availability of real-time product streams.

The igc solution is one of the RTS solutions generated by decoding the real-time product streams. The igc files are derived from the IGC01 solution, which uses the real-time data streams that are referred to the satellite center-of-mass (CoM).

• orbit files (igcWWWWD.sp3.Z) contain the decoded orbit and clock results from the IGC01 real time stream at 30 second intervals
• clock solution files (igcWWWWD.clk.Z) consist of decoded clock results from the IGC01 real time stream at 10 second intervals
• solution summary files (ritWWWWD.sum.Z) consist of orbit and clock comparisons of all the AC and combination streams against IGS rapid solution

The CDDIS also provides real-time streaming corrections through its real-time caster. A description of these solutions is available from the IGS RTS website product page.

The starting directory for these files is:

https://cddis.nasa.gov/archive/gnss/products/rtpp

Append the following file names to the starting directory:

WWWW/SSSWWWWD.TYP.Z

as described in the table below.