Welcome to the M3G web site. M3G stands for Metadata Management and distribution system for Multiple GNSS Networks. The system allows to upload, validate, and distribute GNSS station metadata (e.g. site logs) and has been developed primary to serve the EPOS, EPN, and EPN densification GNSS networks.

Using M3G

Prior to uploading any metadata for a station belonging to the EPOS network, M3G must have in its possession a completed and signed EPOS-GNSS Supplier Letter from the Data Supplier, including the information on the Operational Centre responsible for maintaining the station metadata in M3G. This Operational Centre will then receive a login account on the M3G web site.

For stations only included in the EPN or EPN-densification networks, there is no need to provide an EPOS-GNSS Supplier Letter and all EPN Operational Centers will be invited, one at the time, to switch from the present EPN CB on-line site log submission system to M3G.

Visit the Guidelines section for the responsibilities of Data Supplier and Operational Centre.

Site log update

  • Site log updates for stations labelled as "EPN" or "EPN densification" in M3G will automatically flow to the EPN Central Bureau.
  • Site log updates for stations labelled as "EPOS" will automatically flow to the EPOS GNSS Data Gateway.


  • M3G is still under development, but offers already a lot of functions.