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Auteur Marc Crombaghs |
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Titre : The first absolute gravity measurements in the Netherlands : period 1991-1999 Type de document : Rapport Auteurs : Marc Crombaghs, Auteur ; Erik de Min, Auteur ; Govert Strang Van Hees, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2002 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 50 Importance : 27 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-275-7 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] gravimètre absolu
[Termes IGN] levé gravimétrique
[Termes IGN] Pays-BasIndex. décimale : 30.42 Gravimétrie Résumé : (auteur) The determination of the earth’s gravity field is done for various reasons:
- From gravity measurements the geoid can be computed. The geoid is the equipotential surface of the earth at mean sea level. The geoid enables 'levelling with GPS' (Global Positioning System).
- Absolute movements of the earth surface can be detected from gravity changes in time, while conventional levelling yields only relative height changes. With absolute gravity changes one can distinguish land subsidence from sea rise. This is a crucial question in low-lying Netherlands.
- Gravity is interesting from a geophysical point of view because deep tectonic fracture zones can be detected in combination with seismic measurements. This is important for the exploration of oil and gas.
- In oceanography gravity is important because ocean currents can be detected. The combination of gravity observations with satellite altimetry reflects sea topography and large-scale ocean circulation, like the warm Gulf Stream.
This report describes in detail the first high precision absolute gravity measurement in The Netherlands. The measurements were carried out by the Survey Department of Rijkswaterstaat and by the Delft University of Technology, department of Geodesy (former Faculty of Geodesy). The measurements from 1991 and 1993 were performed with financial support from the Netherlands Geodetic Commission (NCG).
The gravity units microgal and milligal are used frequently in this rapport. One milligal = 1000 microgal = 10-5 ms-2. The worldwide mean gravity value eqauls 980000 milligal (9.80 ms-2), with variations up to 5000 milligal. In The Netherlands gravity values increase from south to north with about 1 milligal per kilometer. Smallest values occur in Limburg (981100 milligal), while the largest values occur in Groningen (981350 milligal). Local variations are limited to 1 milligal over some kilometers.Numéro de notice : 15021 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport de recherche DOI : sans En ligne : https://www.ncgeo.nl/downloads/50Crombaghs.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=55042 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 15021-01 30.42 Livre Centre de documentation Géodésie Disponible