International Geologiical Congress - Oslo 2008


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IEI-12 Geological maps in the digital era: Quo Vadis?


The World Gravity Map (WGM) project: Objectives and status


Sylvain Bonvalot, Bureau Gravimetrique International, CNES-IRD-CNRS (France)
Michel Sarrailh, Bureau Gravimetrique International, CNES-IRD-CNRS (France)
Anne Briais, Bureau Gravimetrique International, CNES-IRD-CNRS (France)
Richard Biancale, Bureau Gravimetrique International, CNES-IRD-CNRS (France)
BGI Team, Observatoire Midi-Pyrénées (France)


The WGM project is a gravity mapping project undertaken under the aegis of the Commission for the Geological Map of the World (CGMW) in order to complement a set of global geological and geophysical digital maps published and updated by CGMW. Following the example of the World Digital Magnetic Anomaly Map (WDMAM) and of the World Stress Map (WSM), released in 2007 (, this new global digital map aims to provide a high resolution picture of the gravity anomalies of the world based on the up-to-date available information on the Earth gravity field.
The WGM project is conducted by the International Gravity Bureau (IGB), a center of the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG) with the support of the United Nations Educational Scientific and Cultural Organization (UNESCO). This project will benefit from recent improvements provided by the gravity and altimetry satellite missions on global or regional gravity models. Major contributions should include the official EGM08 global model, planned to be released by the National Geospatial-Intelligence Agency (NGA, USA) in the upcoming months, as well as the new global ocean gravity field derived from satellite altimetry DNSC07 computed at the Danish National Space Center (DTU- Denmark). Additional gravity data (land, marine and airborne measurements) available from international or national databases or collected from recent surveys should be also included. Data processing centers will be identified to contribute to the data compilation and validation for the WGM project.
The WGM project will consist in a printed map (1:50 000000) and accompanying digital grids of gravity anomalies and disturbances (including corrections for free air, Bouguer, terrain and atmospheric effects). Recent recommendations on the definition of gravity anomalies will be taken into account to homogenize the global information provided by satellite geodesy on the ellipsoid surface (horizontal and vertical reference frames and datum), on the geoid and on the oceanic and topography surfaces. The information provided by the worldwide absolute gravity measurements will be also incorporated. We present here the main objectives and status of the WGM project within the framework of the new homogeneous set of global geophysical and geological maps provided by the CGMW for educational and research purposes.

IGB Team: S. Bonvalot, R. Biancale, A. Briais, T. Fayard, N. Lestieu, S. Pecquerie, M. Sarrailh, G. Gabalda


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