The EPN (or EUREF Permanent Network) is a voluntary organization of several European agencies and universities that pool resources and permanent GNSS station data to generate precise GNSS products. The EPN has been created under the umbrella of the International Association Geodesy and more precisely by its sub-commission EUREF.

The EPN does not manufacture or sell any equipment. It also does not endorse equipment (although the EPN has functional requirements for the GNSS equipment at EPN stations specified in the Guidelines for EPN stations and Operational Centres).

GNSS stands for Global Navigation Satellite System. Currently operating GNSS's are the American GPS, the Russian GLONASS, the European Galileo, the Chinese BEIDOU, and the Japanese QZSS.

This is provided by the U.S. Department of Homeland Security.

This is provided by the GLONASS centre.

This is provided by the European GNSS Service Centre.

An extensive number of papers related to the EPN is available from the EPN CB.

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 EPN requires redundancy and multi-year commitments to ensure reliability. To help EPN agencies justify funding requests, we request that users include a citation when using EPN data or products in a publication. We suggest:
 
Bruyninx C., H. Habrich, W. Sõhne, A. Kenyeres, G. Stangl, C. Võlksen, 2012, Enhancement of the EUREF Permanent Network Services and Products, "Geodesy for Planet Earth", IAG Symposia Series, Vol 136, pp. 27-35, DOI 10.1007/978-3-642-20338-1_4

The International GNSS Service (IGS) is a voluntary federation of 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 GNSS community (source: IGS CB).
The EPN is a dense regional network GNSS network that operates following IGS standards. In addition, the IGS considers the EPN as a related network and IGS works closely with the agencies operating the EPN. Typically, the IGS designates a subset of the regional EPN stations 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. Next to this, the EPN uses IGS products (such as the IGS precise satellite orbits for the generation of the EPN products).

Precise satellite orbits are made available by the IGS. Check the IGS web-site and more specific the page where you can download ephemeris.

By "data" we mean raw GPS/GLONASS pseudorange and phase observations, broadcast ephemerides, and supporting types of raw data (such as meteorological) as they are gathered by the permanent tracking stations. Data are mostly provided in the RINEX format (see RINEX formats web page).
We use the term "products" for things like the precise estimated station coordinates, tropospheric zenith path delays and the coordinate time series. The products are generated through analysis of the raw station data.
Both raw data and EPN products are available from the EPN Data Centres and/or the Central Bureau.

The EPN has an open data policy. All observation data and products are available without charge from the EPN data centres and/or Central Bureau.
Although the EPN 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 EPN data and products is the sole responsibility of the user.
When your use of EPN data or products results in a publication, please include a citation. You can choose from our publications web page.

The EPN uses exactly the same formats as the IGS does. See the EPN Formats web page or IGS list.

The EPN products are described in our web site in Section "Products and Services".
EPN products are formed from a combination of results submitted by the EPN Analysis Centres. In this way, the EPN products benefit in precision, accuracy, stability, reliability, and robustness compared to the results of any individual AC.

See the files in https://epncb.oma.be/pub/center/analysis/, which are submitted by the ACs.

This web page lists the different reference frames. Transformation formula between the frames are available from the ITRF web page's Transformation Parameters page https://itrf.ign.fr/en/solutions/transformations. The EPN CB also provides an on-line coordinate transformation service.

An EPN station conforms to the "Guidelines for EPN stations and Operational Centres" and is listed on EPN network maps and lists.

Each user of the GNSS observation data from an EPN station requires a minimal amount of information about the station such as its location, the GNSS equipment used, its monumentation, possible co-locations with other instruments and addresses of site operators. The station log is the file that maintains all this information (including the history) in a machine readable format. Having a valid station log is one of the mandatory requirements for EPN stations.
Examples of station logs are available from the EPN CB.

If the station is expected to be beneficial to an EPN product (see our Section on "Products and Services"), Working Group, or project, please do. Visit the "Procedure for becoming an EPN station" and follow the instructions.

An overview of available ITRS and ETRS89 coordinates for all EPN stations is available from the EPN CB's coordinates web page. For new EPN stations, approximate coordinates for each station are listed on the station station log.

You can use the EPN CB on-line transformation service.

At the EPN CB, each station has a web page reachable from the clickable map and station list. This page displays data availability and latency (for both the hourly and daily data submissions), errors in the header of the RINEX observation files, coordinate time series and data quality plots.

Please consult our web page with the results of the EPN CB monitoring of data availability and latency.

Have a look at the table "Who is processing which stations ?". Contact persons for each analysis centre can be found on the page where the EPN Analysis Centres are described.

Use M3G system to submit a site log to the EPN CB.
The web page Site log file check only allows to check the format of station site log files and is intended as a service for non-EPN stations. The cheking can be done using the metadata validation critera applied in the EPN, EPN densification, or EPOS networks. The output of the cheking will be displayed on-screen. No login is required.

The antenna height of a station is the vertical height difference between the antenna marker on the ground and the Antenna Reference Point (ARP). The file antenna.gra describes for each antenna used within the IGS and EPN the conventional Antenna Reference Point that should be used to determine the antenna height.
The antenna.gra file is maintained by the IGS Central Bureau.

If the GNSS station is moved to a new monument (eg because of a destruction of the old monument), then a new DOMES number must be requested from the IERS and a new 4-char ID is required. It is imperative to contact the EPN CB in order to decommission the EPN station on the old marker and propose a new EPN station, with the new 4-char ID and new DOMES number, for introduction in the EPN.

See the Guidelines for EPN stations and Operational Centres and the more specific web-page on EPN equipment and calibration.

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

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

To be sure everyone recognizes the type of GNSS observation equipment used in at a GNSS observation station, the IGS defines standard names for the different GNSS equipment (antennae, receivers, radomes) available today. The rcvr_ant.tab file contains the list of these standard names. Since the EPN uses the same standards as the IGS, it also uses the same naming conventions. These conventions are used in the files of the GNSS observation data files and the IGS and EPN products.
The rcvr_ant.tab file is maintained by the IGS Central Bureau. Requests for updates should be sent to the IGS Central Bureau with a copy to the EPN Central Bureau.

The igs20.atx file contains the absolute phase eccentricity values of the antennae used within the IGS and the EPN.
The igs20.atx file is maintained by the IGS Central Bureau. Requests for updates should be sent to IGS Central Bureau with a copy to the EPN Central Bureau.

The epn_20.atx file contains with the absolute antenna phase centre calibrations for all the EPN stations; it merges the individual antenna calibrations and the calibrations available from the IGS in the file igs20.atx. Access to the files is provided through the EPN file server and from the Equipment & Calibration web page.
Different to the IGS, EUREF has decided to take advantage of the fact that several EPN stations have absolutely calibrated their antenna+radome equipment (see EUREF mail 3020). If available, EUREF will used these 'individual' calibrations for modeling the antenna phase center of the EPN stations. For stations that do not have individual absolute calibrations, the EPN will use the absolute calibration values made available by the IGS.
epn_20.atx is the official table to be used in the EPN analysis, while igs20.atx is the official table to be used in the IGS analysis.
To include an individual antenna calibration in epn_20.atx, contact the EPN Central Bureau. To update the igs20.atx file, see 4.5. More details can be found here.

Not necessarily. The Guidelines for EPN stations and Operational Centres establish functional requirements for equipment in the EPN network.