Descripteur
Documents disponibles dans cette catégorie (801)
Ajouter le résultat dans votre panier
Visionner les documents numériques
Affiner la recherche Interroger des sources externes
Etendre la recherche sur niveau(x) vers le bas
Effects of space weather on GOCE electrostatic gravity gradiometer measurements / Elmas Sinem Ince in Journal of geodesy, vol 90 n° 12 (December 2016)
[article]
Titre : Effects of space weather on GOCE electrostatic gravity gradiometer measurements Type de document : Article/Communication Auteurs : Elmas Sinem Ince, Auteur ; Spiros D. Pagiatakis, Auteur Année de publication : 2016 Article en page(s) : pp 1389 - 1403 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] champ magnétique local
[Termes IGN] géophysique externe
[Termes IGN] gradient de gravitation
[Termes IGN] gradiomètre
[Termes IGN] perturbation ionosphérique
[Termes IGN] pôleRésumé : (Auteur) We examine the presence of residual nongravitational signatures in gravitational gradients measured by GOCE electrostatic gravity gradiometer. These signatures are observed over the magnetic poles during geomagnetically active days and can contaminate the trace of the gravitational gradient tensor by up to three to five times the expected noise level of the instrument (∼11 mE). We investigate these anomalies in the gradiometer measurements along many satellite tracks and examine possible causes using external datasets, such as interplanetary electric field measurements from the ACE (advanced composition explorer) and WIND spacecraft, and Poynting vector (flux) estimated from equivalent ionospheric currents derived from spherical elementary current systems over North America and Greenland. We show that the variations in the east-west and vertical electrical currents and Poynting vector components at the satellite position are highly correlated with the disturbances observed in the gradiometer measurements. The results presented in this paper reveal that the disturbances are due to intense ionospheric current variations that are enhanced by increased solar activity that causes a very dynamic drag environment. Moreover, successful modelling and removal of a high percentage of these disturbances are possible using external geomagnetic field observations. Numéro de notice : A2016-809 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0931-8 En ligne : http://dx.doi.org/10.1007/s00190-016-0931-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82601
in Journal of geodesy > vol 90 n° 12 (December 2016) . - pp 1389 - 1403[article]On the spectral combination of satellite gravity model, terrestrial and airborne gravity data for local gravimetric geoid computation / Tao Jian in Journal of geodesy, vol 90 n° 12 (December 2016)
[article]
Titre : On the spectral combination of satellite gravity model, terrestrial and airborne gravity data for local gravimetric geoid computation Type de document : Article/Communication Auteurs : Tao Jian, Auteur ; Yan Ming Wang, Auteur Année de publication : 2016 Article en page(s) : pp 1405 - 1418 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse harmonique
[Termes IGN] bruit blanc
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] erreur
[Termes IGN] géoïde gravimétrique
[Termes IGN] géoïde local
[Termes IGN] Texas (Etats-Unis)
[Termes IGN] varianceRésumé : (Auteur) One of the challenges for geoid determination is the combination of heterogeneous gravity data. Because of the distinctive spectral content of different data sets, spectral combination is a suitable candidate for its solution. The key to have a successful combination is to determine the proper spectral weights, or the error degree variances of each data set. In this paper, the error degree variances of terrestrial and airborne gravity data at low degrees are estimated by the aid of a satellite gravity model using harmonic analysis. For higher degrees, the error covariances are estimated from local gravity data first, and then used to compute the error degree variances. The white and colored noise models are also used to estimate the error degree variances of local gravity data for comparisons. Based on the error degree variances, the spectral weights of satellite gravity models, terrestrial and airborne gravity data are determined and applied for geoid computation in Texas area. The computed gravimetric geoid models are tested against an independent, highly accurate geoid profile of the Geoid Slope Validation Survey 2011 (GSVS11). The geoid computed by combining satellite gravity model GOCO03S and terrestrial (land and DTU13 altimetric) gravity data agrees with GSVS11 to ±1.1 cm in terms of standard deviation along a line of 325 km. After incorporating the airborne gravity data collected at 11 km altitude, the standard deviation is reduced to ±0.8 cm. Numerical tests demonstrate the feasibility of spectral combination in geoid computation and the contribution of airborne gravity in an area of high quality terrestrial gravity data. Using the GSVS11 data and the spectral combination, the degree of correctness of the error spectra and the quality of satellite gravity models can also be revealed. Numéro de notice : A2016-810 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0932-7 En ligne : http://dx.doi.org/10.1007/s00190-016-0932-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82602
in Journal of geodesy > vol 90 n° 12 (December 2016) . - pp 1405 - 1418[article]On the usefulness of relativistic space-times for the description of the Earth’s gravitational field / Michael Soffel in Journal of geodesy, vol 90 n° 12 (December 2016)
[article]
Titre : On the usefulness of relativistic space-times for the description of the Earth’s gravitational field Type de document : Article/Communication Auteurs : Michael Soffel, Auteur ; Francisco Frutos, Auteur Année de publication : 2016 Article en page(s) : pp 1345 - 1357 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] coordonnées cartésiennes géocentriques
[Termes IGN] espace-temps
[Termes IGN] relativité générale
[Termes IGN] système de référence géodésiqueRésumé : (Auteur) The usefulness of relativistic space-times for the description of the Earth’s gravitational field is investigated. A variety of exact vacuum solutions of Einstein’s field equations (Schwarzschild, Erez and Rosen, Gutsunayev and Manko, Hernández-Pastora and Martín, Kerr, Quevedo, and Mashhoon) are investigated in that respect. It is argued that because of their multipole structure and influences from external bodies, all these exact solutions are not really useful for the central problem. Then, approximate space-times resulting from an MPM or post-Newtonian approximation are considered. Only in the DSX formalism that is of the first post-Newtonian order, all aspects of the problem can be tackled: a relativistic description (a) of the Earth’s gravity field in a well-defined geocentric reference system (GCRS), (b) of the motion of solar system bodies in a barycentric reference system (BCRS), and (c) of inertial and tidal terms in the geocentric metric describing the external gravitational field. A relativistic SLR theory is also discussed with respect to our central problem. Orders of magnitude of many effects related to the Earth’s gravitational field and SLR are given. It is argued that a formalism with accuracies better than of the first post-Newtonian order is not yet available. Numéro de notice : A2016-806 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0927-4 En ligne : http://dx.doi.org/10.1007/s00190-016-0927-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82594
in Journal of geodesy > vol 90 n° 12 (December 2016) . - pp 1345 - 1357[article]Problems and methods of calculating the Legendre functions of arbitrary degree and order / Elena Novikova in Geodesy and cartography, vol 65 n° 2 (December 2016)
[article]
Titre : Problems and methods of calculating the Legendre functions of arbitrary degree and order Type de document : Article/Communication Auteurs : Elena Novikova, Auteur ; Alexander Dmitrenko, Auteur Année de publication : 2016 Article en page(s) : pp 289 - 312 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Earth Gravity Model 2008Résumé : (auteur) The known standard recursion methods of computing the full normalized associated Legendre functions do not give the necessary precision due to application of IEEE754-2008 standard, that creates a problems of underflow and overflow. The analysis of the problems of the calculation of the Legendre functions shows that the problem underflow is not dangerous by itself. The main problem that generates the gross errors in its calculations is the problem named the effect of “absolute zero”. Once appeared in a forward column recursion, “absolute zero” converts to zero all values which are multiplied by it, regardless of whether a zero result of multiplication is real or not. Three methods of calculating of the Legendre functions, that removed the effect of “absolute zero” from the calculations are discussed here. These methods are also of interest because they almost have no limit for the maximum degree of Legendre functions. It is shown that the numerical accuracy of these three methods is the same. But, the CPU calculation time of the Legendre functions with Fukushima method is minimal. Therefore, the Fukushima method is the best. Its main advantage is computational speed which is an important factor in calculation of such large amount of the Legendre functions as 2 401 336 for EGM2008. Numéro de notice : A2016-979 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article DOI : 10.1515/geocart-2016-0017 En ligne : https://doi.org/10.1515/geocart-2016-0017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83696
in Geodesy and cartography > vol 65 n° 2 (December 2016) . - pp 289 - 312[article]Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity / Laurent Métivier in Earth and planetary science letters, vol 452 (October 2016)
[article]
Titre : Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity Type de document : Article/Communication Auteurs : Laurent Métivier , Auteur ; Lambert Caron, Auteur ; Marianne Greff-Lefftz, Auteur ; Gwendoline Pajot-Métivier , Auteur ; Luce Fleitout, Auteur ; Hélène Rouby , Auteur Année de publication : 2016 Article en page(s) : pp 146 - 156 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Amérique du nord
[Termes IGN] anomalie de pesanteur
[Termes IGN] déformation de la croute terrestre
[Termes IGN] gradient de gravitation
[Termes IGN] manteau terrestre
[Termes IGN] paléocontinent
[Termes IGN] viscositéRésumé : (auteur) The Earth's surface was depressed under the weight of ice during the last glaciations. Glacial Isostatic Adjustment (GIA) induces the slow recession of the trough that is left after deglaciation and is responsible for a contemporary uplift rate of more than 1 cm/yr around Hudson Bay. The present-day residual depression, an indicator of still-ongoing GIA, is difficult to identify in the observed topography, which is predominantly sensitive to crustal heterogeneities. According to the most widespread GIA models, which feature a viscosity of 2–3×1021 Pa s2–3×1021 Pa s on top of the lower mantle, the trough is approximately 100 m deep and cannot explain the observed gravity anomalies across North America. These large anomalies are therefore usually attributed to subcontinental density heterogeneities in the tectosphere or to slab downwelling in the deep mantle.
Here, we use observed gravity gradients (GG) to show that the uncompensated GIA trough is four times larger than expected and that it is the main source of the North American static gravity signal. We search for the contribution to these GGs from mantle mass anomalies, which are deduced from seismic tomography and are mechanically coupled to the global mantle flow. This contribution is found to be small over Laurentia, and at least 82% of the GGs are caused by GIA. Such a contribution from GIA in these GG observations implies a viscosity that is greater than 1022 Pa s1022 Pa s in the lower mantle.
Our conclusions are a plea for GIA models with a highly viscous lower mantle, which confirm inferences from mantle dynamic models. Any change in GIA modelling has important paleoclimatological and environmental implications, encouraging scientists to re-evaluate the past ice history at a global scale. These implications, in turn, affect the contribution of bedrock uplift to the contemporaneous mass balance over Antarctica and Greenland and thus the present-day ice-melting rate as deduced from the GRACE space mission. Additionally, studies of the thermo-chemical structure of the lithosphere/crust under North America that exploit gravity or geodetic data should be corrected for a GIA model, which is not the case today.Numéro de notice : A2016-906 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.epsl.2016.07.034 Date de publication en ligne : 16/08/2016 En ligne : http://dx.doi.org/10.1016/j.epsl.2016.07.034 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83034
in Earth and planetary science letters > vol 452 (October 2016) . - pp 146 - 156[article]A conventional value for the geoid reference potential W0 / L. Sánchez in Journal of geodesy, vol 90 n° 9 (September 2016)PermalinkTopographic gravitational potential up to second-order derivatives: an examination of approximation errors caused by rock-equivalent topography (RET) / Michael Kuhns in Journal of geodesy, vol 90 n° 9 (September 2016)PermalinkFast computation of general forward gravitation problems / Fabien Casenave in Journal of geodesy, vol 90 n° 7 (July 2016)PermalinkUtilization of high-resolution EGM2008 gravity data for geological exploration over the Singhbhum-Orissa Craton, India / S.K. Pal in Geocarto international, vol 31 n° 7 - 8 (July - August 2016)PermalinkOn the impact of airborne gravity data to fused gravity field models / Dimitrios Bolkas in Journal of geodesy, vol 90 n° 6 (June 2016)PermalinkJoint analysis of GOCE gravity gradients data of gravitational potential and of gravity with seismological and geodynamic observations to infer mantle properties / Marianne Greff-Lefftz in Geophysical journal international, vol 205 n° 1 (April 2016)PermalinkComparison of Satellite-Only Gravity Field Models Constructed with All and Parts of the GOCE Gravity Gradient Dataset / Sean L. Bruinsma in Marine geodesy, vol 39 n° 3-4 (March - June 2016)PermalinkContribution of mass density heterogeneities to the quasigeoid-to-geoid separation / Robert Tenzer in Journal of geodesy, vol 90 n° 1 (January 2016)PermalinkPermalinkExploring mass variations in the Earth system / Mike Sips in Cartography and Geographic Information Science, Vol 43 n° 1 (January 2016)Permalink