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A legal entity that can act as: Data Supplier, Operational Centre, Data Node, Data Centre, etc.

Centre that analyses GNSS observations, or derived GNSS products, and makes the resulting products (e.g. positions, time series, velocity and strain rate) available to EUREF or EPOS.

Physical location of the GNSS station observation/navigation data.

Identical to Station Owner or Responsible Agency. The Data Supplier is the agency owning the GNSS station and having the legal rights to distribute the data of the GNSS station and to stop its operation. It is possible that the Data Supplier delegates the maintenance of the GNSS station metadata to another agency, which is the Station Metadata Maintainer. In the site log, the Data Supplier is inserted in section 12. "Responsible Agency". In GeodesyML it is inserted in the field "siteOwner".
See also EPOS Data Supplier.

Data Object Identifier (DOI).

Unique number (e.g., "10003M008") attributed by the IERS (International Earth Rotation and Reference System Service) to the reference point of a GNSS station. It can be a physical marker (e.g. a bolt on the ground) or a virtual marker (e.g. centre-bottom of the GNSS antenna). The DOMES number has to be requested from the ITRF web site.

Data and resources are FAIR when they are Findable, Accessible, Interoperable and Reusable

Geodesy Markup Language, a new GML application schema (see developed by the IGS to describe how geodetic data and metadata can be defined and transferred in XML format. This XML-based standard includes objects like antenna, receiver, cable, adjustments etc.

A GNSS network regroups continuously operating GNSS stations managed according to a well-defined set of guidelines e.g., use of common standards for site monumentation, receiver and antenna equipment, data exchange format, etc., and whose observation data flow and data availability are regulated by rules established within the GNSS network.

A GNSS project regroups GNSS stations whose GNSS observation data are used in the products generated within the context of a scientific project or, in other words, whose observation data were collected by the GNSS analysis centers contributing to the project. Examples of M3G projects are the EPN densification project, generating station positions and velocities, and the EUMETNET EIG GNSS water vapour programme (E-GVAP), generating tropospheric products.

A GNSS system, consisting of GNSS equipment (antenna, receiver and associated hardware and software) described in a GNSS site log file (that should in fact be called station log for consistency).

M3G is currently the official provider of GNSS station metadata for the EUREF Permanent Network (EPN), managed by the EPN Central Bureau at the Royal Observatory of Belgium, EPOS-GNSS station network, managed by the Royal Observatory of Belgium.
In addition, M3G provides information on other GNSS networks to which a station contributes: the International GNSS Service (IGS) network, managed by the IGS Central Bureau and the GNSS stations at tide gauges (SONEL), managed by LIENSS

Local or national GNSS networks are networks that group a number of stations operated by one agency or being part of a national GNSS networks.

Software package "Metadata Management and distribution system for Multiple GNSS Networks"

Portal where M3G is running and M3G Registered Agencies maintain the GNSS station metadata:

Identical to Station Metadata Maintainer and Site Metadata Custodian. Agency that has a M3G account and has therefore committed to maintain station metadata in M3G.

On-line form within M3G, which allows inserting information about the Station Metadata Maintainer i.e., Registered Agency, and the stations whose metadata it manages. After saving the form, it exports an MM form.

Identical to 4-char ID for RINEX 2 and 9-char ID for RINEX 3 and later formats.

Identical to the DOMES number.

M3G Object Identifier, for identifying M3G objects e.g. GNSS stations, data centres/nodes, EPOS data suppliers and networks, with a resolvable, unique and persistent identifier.

Local point of contact at a GNSS station, indicated in section 11. of the site log "On-site, Point of Contact". In GeodesyML this information is entered in the field "siteContact".

Agency responsible for including GNSS Station in a given GNSS network or project.

Entering personal contact information (name, email address etc.) in M3G is possible, but discouraged. If M3G is not granted permission to make the personal contact information public, this information will be removed from the site log(s) before publication. Check our privacy policy to know how we handle your personal data.

A non-personal contact e.g. "GNSS team", related to an agency.

Standard Receiver Independent EXchange format for exchanging file-based GNSS observables, navigation data, and meteorological data. Several versions exist.

Solution (Software/technique) INdependent EXchange Format (SINEX)

Geographical physical location where one or more GNSS stations and other Earth Science equipment are installed.

Text-based description description of the metadata of a GNSS station. The format is maintained by the International GNSS Service (IGS), see

Four printable ASCII characters (usually case-insensitive alphanumeric plus underscore) which traditionally have been used to designate a GNSS station and the first 4 characters of its RINEX data file name. Example: "CASC". In cases where multiple GNSS receivers are split off from the same antenna, each GNSS receiver is considered a separate station and a different 4-character ID needs to be defined. The station 4-character ID is not guaranteed to be unique, although in this phase (until full move to station 9-character ID), this must be imposed.

New station ID to be used in replacement of the 4-character ID. The 9-character ID follows the RINEX 3 station naming conventions. The first 4 characters are the station 4-character ID and the last three the ISO country code. The middle two digits (0-9) relate to monument (or marker)/receiver. Until full move to station 9-character ID, the antenna number and receiver number are always "0" and there is a one-to-one relation between the station 4-character ID and its 9-character ID. Example: "CASC" and "CASC00PRT".

Identical to site log

Identical to M3G Registered Agency and SIte Metadata Custodian. Agency that maintains station metadata in M3G and has therefore a M3G account. In most cases, the Station Owner itself acts as Station Metadata Maintainer. However, it is also possible that the Station Owner delegates the maintenance of the station metadata to another agency. Note that in the site log, the contact information relative to the Station Metadata Maintainer which updated the site log is entered in the field "Prepared by" while in GeodesyML, this information is inserted in the field "siteMetaDataCustodian".

Text-based file (e.g. ROB.MM) that describes the information for one Station Metadata Maintainer about the agency acting as Station Metadata Maintainer, its contact information and the stations whose metadata it maintains.
Formerly known as "OC form".

Any agency, different from the Station Metadata Maintainer, but used in the site log or in the setup of networks. The Third-party Agencies are inserted in M3G using the Third-Party Agency Form. Any agency appearing in section 11. or section 12. of a site log maintained by a Station Metadata Maintainer i.e., a M3G Registered Agency, but different from the Station Metadata Maintainer. In other words, Station Owner and Station Metadata Maintainer are two different agencies.

On-line form within M3G, which allows inserting information about the agencies involved in the operation of the stations managed by a Station Metadata Maintainer i.e., Third-party Agencies. These agencies can act as on-site contact, stations owners, network managers, etc.

Permanent GNSS tracking receivers and antennae

Virtual networks are GNSS networks that are set up by the M3G administrator at the request of a group of station managers. They allow to indicate in M3G a set of GNSS stations focusing on a common objective e.g., the VOLC virtual network including EPOS GNSS stations around volcanoes.


Provides access to the metadata and data from the EPOS-GNSS stations.

Monitors EPOS-GNSS station observation data quality and metadata consistency, and provides feedback to station operators through a web portal and email alerts.

Virtualization layer on top of one (or more) Data Centre(s). Using the GLASS software, the Data Node makes the GNSS station data at Data Centers (or data repositories) globally discoverable at the EPOS-GNSS data gateway and also locally at the data local node

This contact is responsible for the operational running of a GLASS Node.

Description of the service supplied by a Data Node. This contract specifies the stations and types of data it may consider accepting in terms of its geographical extent and other attributes.

Letter to be signed by a Data Supplier (or station owner) and provided to the M3G-bureau. It gives EPOS the permission to distribute its GNSS data.

For EPOS stations, the Data Supplier signs the EPOS-GNSS Data Supplier Letter.

Encoding format used within EPOS

Main gateway/portal of the EPOS project. This portal as well as providing access to GNSS data and products allow access to multidisciplinary data, products (including synthetic data from simulations, processing and visualization tools), and services to different stakeholders, including users from the scientific community and industrial partners.

Integrated software package that is deployed in a GNSS infrastructures contributing to EPOS in order to manage GNSS data and metadata.

Provides access to GNSS products computed in the scope of the EPOS. Products are made available for download to users in various formats.