IGS FAQ

The IGS is a voluntary federation of many worldwide agencies that pool resources and permanent GNSS station data to generate precise GNSS products. In general, you can think of the IGS as the highest-precision international civilian GPS community.

GNSS stands for Global Navigation Satellite System. Currently operating GNSS's are GPS (U.S.A.'s Global Positioning System) and GLONASS (Russia's Global Navigation Satellite System). Another GNSS planned for the future is Europe's Galileo.

The IGS Governing Board voted to change the name to the International GNSS Service, to recognize the incorporation of GLONASS and intent to incorporate future GNSS as well.

This is provided by the U.S Coast Guard's Navigation Center.

The results of the latest IGS Ultrarapid analysis indicate how well the IGS was able to determine the GPS satellites' orbits.

This is provided by the GLONASS center.

You are welcome to browse our global network data and see if nearby IGS stations were recording data from the GPS satellites. Reports of GPS problems are accepted by the U.S Coast Guard's Navigation Center.

Each participating organization voluntarily brings its own funding according to its own mission. These organizations tend to be public or government institutions or other research organizations. Consequently, the IGS requires redundancy and/or multi-year commitments from important components to ensure reliability. To help IGS agencies justify funding requests, we request that users include a citation when use of IGS data or products results in a publication. We suggest

By "data" we mean raw GPS/GLONASS pseudorange and phase observations, broadcast ephemerides, and supporting types of raw data (such as meteorological).

We use the term "products" for things like precise orbit and clock files, which are generated through analysis of the raw site data.

The IGS has an open data policy. All of the present suite of products are available without charge from the IGS data centers.

Although the IGS strives for the highest quality of data and data products, it can not make any warranty, express or implied, or assume any legal liability or responsibility for the accuracy, completeness or usefulness of any information or product. Use of the IGS data and products is the sole responsibility of the user.

When your use of IGS data or products results in a publication, please include a citation. We suggest

See the list.

A table outlining each data type, including sampling intervals, formats, and access details, is kept up-to-date at http://igscb.jpl.nasa.gov/components/data.html.

A table of products with their update schedules, formats, accuracies, access details, etc. is available at http://igscb.jpl.nasa.gov/components/prods.html"

From the Charter for IGS Analysis Centers and Associate Analysis Centers":"IGS products are formed from a combination of independent results submitted by the IGS Analysis Centers. To the extent that the effect of data and mismodeling among different Analysis Centers are independent, properly weighted combinations of results can be superior. In this way, the IGS products benefit in precision, accuracy, stability, reliability, and robustness compared to the results of any individual AC."

The IGS Analysis Center Coordinator's page is also an informative source about recent performance of the classic IGS products.

These are the submissions to the IGS combined product generated by each IGS Analysis Center (AC), but the official IGS products are the combinations formed by coordinators from the solutions submitted by each AC. IGS products can be recognized by their filenames, as detailed in the product access information available from the rightmost column of the product table.

See the files in http://igscb.jpl.nasa.gov/igscb/center/analysis, which are submitted by the ACs.

See "A Guide to Using IGS Products" by J. Kouba in the publications area of the IGS website.

You can find satellite antenna offset and PCV information in the IGS absolute antenna file igs05.atx.

This is covered in "A Guide to Using IGS Products". An archive of the discussion leading to this decision is available. Please note that this convention is subject to change as the IGS refines its antenna offset treatment.

All IGS orbits and clocks refer to the satellite center of mass (CM).

Here are a couple references on interpolation methods:

Here are a couple references.

An IGS station conforms to the IGS Site Guidelines and is listed on IGS network maps and lists

These are dense regional networks composed of stations that in most cases meet the IGS Site Guidelines. They are considered to be related networks and the IGS works closely with the agencies which operate them. Typically, a subset of a regional network's stations is designated also as IGS stations. The choice of which stations should also be IGS stations is motivated by their benefit to the IGS products, according to location and instrumentation.

If it is expected to be beneficial to an IGS product or project, please do. See the IGS new station checklist.

Approximate coordinates for each site are listed on the Station list page. Precise coordinates, in the ITRF reference frame, are available from the ITRF. Weekly station solutions in SINEX format can be located via the "Geocentric Coordinates of IGS Tracking Stations" part of the product table

See Q: 4.7.

Each site has a web page reachable from the clickable map and station list. This has daily-updated graphs of how the station's latency and data compare with that of other IGS sites. Significant data outages will be flagged on these pages as well.

Site operators are to send significant station event notices to the IGSStation mailing list.

See the IGS Site Guidelines.

No, the IGS maintains vendor neutrality and instead publishes functional requirements.

We do not issue certifications, but we can ask an IGS analyst to examine sample data sets from new equipment types and comment.

You could, for example, refer them to this faq to demonstrate that the IGS does not endorse or cerfity equipment, or assert whether the equipment meets IGS functional guidelines.

The data is archived permanently and used in long-term studies. There are therefore questions that arise about models which are no longer current, and it is helpful to have familiarity with historical products.

It is also necessary for the IGS to establish what observables are directly tracked by each receiver type. We can determine this from data, but appreciate information from the manufacturer as well. Please see IGSMail #2320 (24 Jun 1999) in the archives at http://igscb.jpl.nasa.gov

Not necessarily. The IGS Site Guidelines establish functional requirements for equipment in the IGS network. The Central Bureau can arrange for an analysis center to examine sample data from new equipment types and comment on its suitability for the IGS.

Please read over the IGS Site Guidelines and take note of things like the necessary antenna calibration, and requested settings such as recording data from satellites marked unhealthy.

Please see the IGS Site Guidelines.

The Network Coordinator at the Central Bureau, igscb @ igscb.jpl.nasa.gov can be your point of contact any time you are not sure where to turn.

At the moment, the file igs05.atx contains all corrections available either from Geo++ or from NGS. The only prerequisite is the presence of an official IGS anteanna name within rcvr_ant.tab. You may seek additional info from the IGS Antenna Working Group.

• Reference 1
• Reference 2

Please see IGSMail #4463.
Also, it is not allowed to enter a new antenna and radome combination into the IGS if absolute calibration results are not available. In addition, in cases of missing radome calibration, the phase center corrections for the corresponding antenna without the radome are used. Another important point could be the problem(s) of adding calibrations for combinations that are already in use. For reasons of consistency, this is not always possible.

igs_01.pcv is the official table to be used in IGS analysis. And yes, it does differ from NGS' latest table, and even if you look closely, also from NGS' previous table. The history is that some years back, NGS and other groups doing calibrations collaborated to make a definitive IGS table by averaging the various measurements available. Some time later the NGS table you see now came out. We have not updated the IGS values to NGS' latest in all cases for a few reasons:

We currently have an ad-hoc committee which is working to obtain quality satellite pcv tables, which would enable use of absolute rather than relative calibrations in a future update of the igs_01.pcv file.

At present, when we get an antenna not yet in igs_01.pcv, we inquire with a few regional networks such as EUREF whether they have any calibrations for it, and if not, we add the current NGS value.

In short, if you are doing IGS analysis you should be using igs_01.pcv. If not you should just be certain whatever you choose is consistent with your requirements.

Follow the link(s) from the Mail area and confirm that your message meets the subject guidelines for that list.

To send a message to an IGS mailing list, email it to listname@igscb.jpl.nasa.gov , substituting the listname (igsmail, igsstation, igs-rtwg, etc.) for listname.

Please ensure the first line of the body of your message starts with the string "Author: " followed by the names of the author(s) of the message. Also, the Subject field of the email should not be blank.

For example, the following text meets the format (if not content) requirements for IGS Mail if sent in a plain text email with a non-null Subject field.