What is the RGF93 ?

In metropolitan France, the official geodetic system is the RGF93, it allows to materialize a precise reference point on the metropolitan territory while adapting to modern technologies. Compatible with worldwide references, the RGF93 is a component of the European ETRS89 system.

As part of the maintenance of national geodetic references, the IGN ( National Institute of Geographic and Forestry Information), a TERIA partner, has recalculated all the data of the Permanent GNSS Network for the period 1998-2019.

With an impact of less than a centimetre, these updates have been migrated without any interruption in service to ensure accurate and consistent results for your measurements.

Some history

The RGF93 succeeds the old French geodetic system, the New Triangulation of France or NTF (French article). This old process allowed the materialisation of landmarks by angular measurements from the end of the 19th century onwards. (More information on the IGN website)

Faced with the deployment of the GNSS system in 1989, the observation is simple : the NTF no longer met the needs of surveyors or topographical surveys. From then on, the RGF93 was born.

The principle of RGF93 :

The RGF93 provides concrete access to a geodetic system.

It can be :

  • Materialised” thanks to a set of physically defined points (terminals, markers) whose coordinates are known in the RGF.
  • Active“, represented by all the permanent GNSS stations in the RGP (Permanent GPS Network)
RGF (French Geodetic Network)
Consists of 3 parts :

  • RRF : French Reference Network with 23 points determined by spatial geodesy
  • RBF : French Base Network made up of 1009 sites determined by spatial geodesy
  • RDF : French Retail Network composed of NTF sites whose coordinates have been recalculated in RGF93
RGP (Permanent GPS Network)

The Network is in constant evolution: 517 stations currently

Find the list of stations on the official IGN website: http://rgp.ign.fr/STATIONS/liste.php0

RGF93 specifications :

  • Three-dimensional geocentric
  • Linked to the global reference system ITRS (International Terrestrial Reference System)
  • Associated with the ellipsoid IAG GRS 1980
  • Using the international meridian (Greenwich meridian) as the original meridian
  • Associated projections are the Lambert-93 projection and the CC 9 Zones projection.
  • Horizontal accuracy between 1 and 2 cm (compared to global systems)
  • Vertical accuracy between 2 and 5 cm (compared to global systems)
  • Suitable for modern positioning technologies
  • The maintenance of the reference system in France

    Since the beginning, several maintenances have been carried out .

    In 2019 – 2020, the IGN carried out maintenance work on the RGF93 by recalculating all the data from the RGP. These recalculations led to coordinate readjustments for some of the stations on the network :

    • IGS antenna calibration updates (86 stations)
    • Own movement of stations and resetting of periodic signals (60 stations)
    • Some error recovery (10 stations)

    To ensure an interoperability between European countries, the RGF93 is strongly based on the European coordinate system (ETRS89), and in particular on its realization ETRF2000 through a theoretical transformation.

    At a time of massive use of PPP calculation methods, many users of centimetric geo-positioning rely on this transformation. However, it has been found that this transformation leads to a bias in the FGR93 results of these users.

    Thus, in order to ensure an optimal access service to the national reference, the IGN has decided to carry out a general maintenance of the RGF93 with effect from 5 January 2021.

    The observed average coordinate changes are as follow :

    EAST : -2,6 mm

    NORTH : -2,8 mm

    HEIGHT : -8 mm

    These minimal updates, with an impact of less than a centimetre, have been migrated without any service interruption to ensure consistent measurement results during your surveys and implementations.

    See the release

    (in French)

    source IGN

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