Specific gravimetry action


The Gravimetry specific action is attached to the Gravimetry Thematic Group of Epos-France. It is based on an instrumental park (PIN PGravi) offering scientific teams a range of measurement resources and services for gravity field studies.

The instrument park comprises absolute and relative gravimeters of different classes and technologies, covering a vast range of applications. These sensors can measure spatial or temporal variations in gravity with an accuracy ranging from a few 10-8 g to a few 10-11 g. They are used in laboratories for characterization, calibration, instrumental monitoring or comparison, as well as for permanent or semi-permanent measurements. Some are then used in the field for reconnaissance surveys and the establishment of networks; others are used for continuous monitoring of gravity variations.

These different instruments help to characterize and quantify variations in mass or density occurring near the Earth’s surface or inside the Earth. Complemented by other gravimetric measurement resources available in France from various organizations or from other projects (EquipEx, CPER, etc.), the Epos-France Gravimetry Specific Action is today helping to consolidate a first-rate national gravimetric infrastructure built up over several decades, and making it possible to respond to numerous fundamental and applied research applications in geodesy, geophysics, geology, hydrology, oceanography and metrology, both at home and abroad.

All the resources available today form a gravimetric infrastructure that complements the observations of space-based gravity missions.


The Gravimetry Specific Action Epos-France manages the PGravi national instrument pool and has the following main objectives:

  • to unite the French community around national measurement resources for absolute and relative gravimetry, both continuous and repeated;
  • to maintain and make available to the scientific community reliable, metrological, traceable to the International System of Units (SI) and modern instrumentation that meets users’ needs, and to exchange expertise in the acquisition, processing and exploitation of gravity measurements;
  • to maintain the network of repeated and absolute measurements, and contribute to the monitoring of temporal variations in gravity, based on a set of permanent observatories housing superconducting gravimeters;
  • to maintain the Permanent Gravimetric Network (RPG) and the Repeated Gravimetric Networks (RRG). The RPG comprises five multi-instrumented stations, four of which collocate absolute measurements with measurements of temporal variations in gravity using permanent superconducting gravimeters. The RRGs are the tide gauge RRG (four stations in conjunction with SHOM and SONEL), the polar RRG (five stations in conjunction with IPEV), the collaborative RRG (four stations in conjunction with Rénag and SNOV) and the calibration line (three stations);
  • to support research and development activities in the field of measuring the Earth’s gravity field (including campaigns or observation networks and the development or validation of new-generation sensors);
  • to integrate and promote the work carried out by the user community, both within the framework of national infrastructures and as part of the gravimetric observation strategies promoted by international organizations.

In brief

  • Web site: gravimetrie.epos-france.fr
  • Thematic group: Gravimetry
  • Instrumentation: Absolue et relative, permanente et de terrain
  • Supervisor and contact: Sébastien Merlet, Observatoire de Paris (LNE-Syrte)
  • Technical contact: Nicolas Le Moigne, Oreme (Géosciences Montpellier)
  • Participating partners:  CNRS-Insu, IPGP, OCA, UM, Unistra, UT3
  • Other participants: IUEM, Observatoire de Paris