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A generalized theory of the figure of the Earth : formulae / Chengli Huang in Journal of geodesy, vol 93 n° 3 (March 2019)
Titre : A generalized theory of the figure of the Earth : formulae Type de document : Article/Communication Auteurs : Chengli Huang, Auteur ; Yu Liu, Auteur ; Chenjun Liu, Auteur ; Mian Zhang, Auteur Année de publication : 2019 Article en page(s) : pp 297 - 317 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie
[Termes descripteurs IGN] croute terrestre
[Termes descripteurs IGN] ellipticité (géométrie)
[Termes descripteurs IGN] équation de Clairaut
[Termes descripteurs IGN] figure de la Terre
[Termes descripteurs IGN] surface de référenceRésumé : (Auteur) Traditionally a laterally homogeneous and spherical base Earth model (e.g., the PREM model) is considered as input when computing the Earth’s equipotential surfaces, which are then resulted to be in symmetric shape. However, the Earth, known with a complex distribution of interior material and density, especially in the upper mantle and the crust, cannot be treated as a symmetric sphere. Recently, a CRUST1.0 model of crust layer is published and well accepted. But the effect caused by the asymmetric crust (and mantle) on equilibrium figures of the Earth cannot be analyzed by the traditional theories. A generalized theory of the figure of the Earth to third-order precision is firstly proposed in this paper, as well as the iterative calculation strategy to solve the complex equation system. In order to validate this generalized theory, the degeneration of this generalized theory with the PREM model is made and is compared with traditional theories, and it is shown that the result of this generalized theory, after degeneration, is consistent very well with traditional theory. Meanwhile, the effect (including both the direct and indirect effects) of the crust layer, from the CRUST1.0 model, on the figures of equipotential surfaces of the Earth’s interior, as well as their effects on the global dynamics flattening, will be presented as an application of this theory in accompanying paper. Numéro de notice : A2019-150 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1159-6 date de publication en ligne : 15/06/2018 En ligne : https://doi.org/10.1007/s00190-018-1159-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92488
in Journal of geodesy > vol 93 n° 3 (March 2019) . - pp 297 - 317[article]
Titre : A generalized theory of the figure of the Earth : on the global dynamical flattening Type de document : Article/Communication Auteurs : Chenjun Liu, Auteur ; Chengli Huang, Auteur ; Yu Liu, Auteur ; Mian Zhang, Auteur Année de publication : 2019 Article en page(s) : pp 319 - 331 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie
[Termes descripteurs IGN] aplatissement
[Termes descripteurs IGN] croute terrestre
[Termes descripteurs IGN] isostasie
[Termes descripteurs IGN] manteau terrestre
[Termes descripteurs IGN] moment d'inertie
[Termes descripteurs IGN] noyau terrestre
[Termes descripteurs IGN] rotation de la TerreRésumé : (Auteur) A generalized theory of the figures of the Earth’s interior to a third-order precision of ellipticity is proposed in accompanying paper in which all the odd degree and nonzero order spherical harmonic terms are included. As both the direct and indirect contributions of the asymmetric crust are included, this theory makes a significant improvement for calculating the asymmetric equilibrium figures of the real Earth comparing with the traditional theories which can only deal with the ideal symmetric Earth. The principal moments of inertia (PMOI: A, B, C) and global dynamical flattening (H) are important quantities in studying the rotating Earth. Precession and gravity observations give observation value of H (Hobs≈1/305.4559) with very high precision, while its theoretical calculated value (Htheory≈1/308.5) from traditional theories and a starting symmetric Earth model (like PREM model) is about 1% less than Hobs. Using the new theory in accompanying paper and replacing the homogeneous outermost crust and oceanic layers in PREM with CRUST1.0 model, we recalculate the equilibrium figures of the Earth’s interior and finally get new values of PMOI and Htheory (≈1/304.7167) whose consistency with Hobs are significantly improved to 0.24%. Furthermore, the asymmetric figures of some interesting boundaries, like inner core boundary, core-mantle boundary, are also given as by-products of this work as these boundaries’ figures are key input for studies of their topographic effect on global rotation and geodynamics, like nutation, normal modes, especially like free core nutation. Numéro de notice : A2019-151 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1163-x date de publication en ligne : 22/06/2018 En ligne : https://doi.org/10.1007/s00190-018-1163-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92490
in Journal of geodesy > vol 93 n° 3 (March 2019) . - pp 319 - 331[article]Contribution actuelle de la calotte Antarctique à la variation du niveau marin / Clémence Chupin (2018)
Titre : Contribution actuelle de la calotte Antarctique à la variation du niveau marin Type de document : Mémoire Auteurs : Clémence Chupin, Auteur Editeur : Le Mans : Ecole Supérieure des Géomètres et Topographes ESGT Année de publication : 2018 Autre Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Importance : 83 p. Format : 21 x 30 cm Note générale : bibliographie
Mémoire d'ingénieur ESGT, master PPMD Photogrammétrie, Positionnement et Mesure de DéformationLangues : Français (fre) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes descripteurs IGN] analyse spatio-temporelle
[Termes descripteurs IGN] Antarctique
[Termes descripteurs IGN] bilan de masse
[Termes descripteurs IGN] calotte glaciaire
[Termes descripteurs IGN] déformation verticale de la croute terrestre
[Termes descripteurs IGN] données GRACE
[Termes descripteurs IGN] élasticité
[Termes descripteurs IGN] fonte des glaces
[Termes descripteurs IGN] géoïde local
[Termes descripteurs IGN] image Envisat-ASAR
[Termes descripteurs IGN] levé gravimétrique
[Termes descripteurs IGN] manteau terrestre
[Termes descripteurs IGN] montée du niveau de la mer
[Termes descripteurs IGN] rhéologie
[Termes descripteurs IGN] viscositéIndex. décimale : MPPMD Mémoires de mastère spécialisé Photogrammétrie, Positionnement et Mesures de Déformation Résumé : (auteur) Avec ses 14 millions de km2, la calotte Antarctique représente le plus grand réservoir d’eau
douce de la planète, ce qui en fait un contributeur non négligeable de l’augmentation du niveau marin. Les dernières estimations de son bilan de masse évalue la perte de glace de la calotte à 2.720 ± 1.390 Gt entre 1992 et 2017, ce qui correspond à une hausse du niveau marin d’environ 7.6 ± 3.9 mm [Shepherd et al., 2018]. L’objectif de ce stage est d’utiliser ce bilan de masse moyen pour quantifier l’amplitude des variations du niveau marin. Grâce aux données d’altimétrie et de gravimétrie satellitaire, un modèle des variations spatio-temporelles du bilan de masse est également construit. Le logiciel SELEN ensuite permet de calculer la variation du niveau marin induite par ces deux modèles de fonte.Note de contenu : Introduction
1- Antarctique & niveau marin
2- Modélisation de la variation spatio-temporelle de l’Antarctique
3- Estimation des variations du niveau marin
ConclusionNuméro de notice : 21856 Thématique : POSITIONNEMENT Nature : Mémoire ingénieur ESGT Organisme de stage : Laboratoire Geoazur (CNRS) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91420 Réservation
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Contribution actuelle de la calotte... - pdf auteurAdobe Acrobat PDF
Titre : Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies Type de document : Article/Communication Auteurs : Lambert Caron, Auteur ; Laurent Métivier Année de publication : 2017 Article en page(s) : pp 1126 - 1147 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes descripteurs IGN] ajustement glacio-isostatique
[Termes descripteurs IGN] anomalie de pesanteur
[Termes descripteurs IGN] calotte glaciaire
[Termes descripteurs IGN] élasticité
[Termes descripteurs IGN] gravimétrie spatiale
[Termes descripteurs IGN] manteau terrestre
[Termes descripteurs IGN] méthode de Monte-Carlo par chaînes de Markov
[Termes descripteurs IGN] rhéologieRésumé : (Auteur) Glacial Isostatic Adjustment (GIA) models commonly assume a mantle with a viscoelastic Maxwell rheology and a fixed ice history model. Here, we use a Bayesian Monte Carlo approach with a Markov chain formalism to invert the global GIA signal simultaneously for the mechanical properties of the mantle and the volumes of the ice sheets, using as starting ice models two previously published ice histories. Two stress relaxing rheologies are considered: Burgers and Maxwell linear viscoelasticities. A total of 5720 global palaeo sea level records are used, covering the last 35 kyr. Our goal is not only to seek the model best fitting this data set, but also to determine and display the range of possible solutions with their respective probability of explaining the data. In all cases, our a posteriori probability maps exhibit the classic character of solutions for GIA-determined mantle viscosity with two distinct peaks. What is new in our treatment is the presence of the bi-viscous Burgers rheology and the fact that we invert rheology jointly with ice history, in combination with the greatly expanded palaeo sea level records. The solutions tend to be characterized by an upper-mantle viscosity of around 5 × 1020 Pa s with one preferred lower-mantle viscosities at 3 × 1021 Pa s and the other more than 2 × 1022 Pa s, a rather classical pairing. Best-fitting models depend upon the starting ice history and the stress relaxing law. A first peak (P1) has the highest probability only in the case with a Maxwell rheology and ice history based on ICE-5G, while the second peak (P2) is favoured for ANU-based ice history or Burgers stress relaxation. The latter solution also may satisfy lower-mantle viscosity inferences from long-term geodynamics and gravity gradient anomalies over Laurentia. P2 is also consistent with large Laurentian and Fennoscandian ice-sheet volumes at the Last Glacial Maximum (LGM) and smaller LGM Antarctic ice volume than in either ICE-5G or ANU. Exploration of a bi-viscous linear relaxing rheology in GIA now seems logical due to a new set of requirements to satisfy observations of transient post-seismic flow seen so ubiquitously in space gravimetry and other global geodetic data. Numéro de notice : A2017-402 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggx083 date de publication en ligne : 27/02/2017 En ligne : https://doi.org/10.1093/gji/ggx083 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86108
in Geophysical journal international > vol 209 n° 2 (May 2017) . - pp 1126 - 1147[article]
Titre : Gravity forward modeling with a tesseroid-based rock-water-ice approach : Theory and applications in the context of the GOCE mission and height system unification Type de document : Thèse/HDR Auteurs : Thomas Grombein, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2017 Collection : DGK - C Sous-collection : Dissertationen num. 798 Importance : 222 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5210-9 Note générale : bibliographie
Inaugural dissertation for the fulfillment of the requirements for the academic degree of Doctor of Engineering (Dr.-Ing.) accepted by the Department of Civil Engineering, Geo and Environmental Sciences of the Karlsruhe Institute of Technology (KIT)
Diese Dissertation ist auf dem Server der Deutschen Geodätischen Kommission unter <http://dgk.badw.de/> sowie auf dem Server des Karlsruher Instituts für Technologie unter <http://dx.doi.org/10.5445/KSP/1000068500> elektronisch publiziertLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes descripteurs IGN] champ de pesanteur terrestre
[Termes descripteurs IGN] données GOCE
[Termes descripteurs IGN] eau de surface
[Termes descripteurs IGN] glace
[Termes descripteurs IGN] gradient de gravitation
[Termes descripteurs IGN] isostasie
[Termes descripteurs IGN] levé gravimétrique
[Termes descripteurs IGN] ondelette
[Termes descripteurs IGN] problème des valeurs limites
[Termes descripteurs IGN] tesseroidRésumé : (auteur) Due to the increasing availability of global high-resolution digital terrain models (DTMs), it has nowadays become possible to obtain a detailed image of the Earth’s topography. This enables to precisely determine the gravitational effect of the topographic masses on the Earth’s gravity field. The central technique for this aim is gravity forward modeling (GFM), which is based on Newton’s law of universal gravitation, and allows to convert topographic heights along with suitable density assumptions into corresponding values of the gravitational potential and its derivatives. This topographic gravity forward modeling attracts a growing interest in various areas of geodetic gravity field determination and geophysical studies of the Earth’s composition and structure (e.g., solid-earth sciences). However, previous GFM methods have proven unsuitable for the increasing accuracy requirements stemming from an improved precision of geodetic measurements. This is due to commonly used simplifications and approximations, such as (i) the use of condensed heights for water and ice masses (rock-equivalent heights), (ii) mass discretizations or arrangements based on planar and spherical approximations, and (iii) assumptions regarding the spectral consistency between band-limited topographic heights and induced gravity, as in residual terrain modeling (RTM) techniques. This thesis contributes to state-of-the-art GFM in the space domain by providing effective techniques and refinements that overcome these limitations. More concretely, the theory of the Rock-Water-Ice (RWI) approach is developed that encompasses a more realistic modeling of the Earth’s topographic and isostatic masses, i.e., the masses of the continents, oceans, lakes, ice sheets and shelves, as well as their deeper lying (isostatic) compensation masses in the Earth’s interior. The RWI method is characterized by a three-layer decomposition of the Earth’s topography that accounts for a rigorous separate modeling of the rock, water, and ice masses with variable density values. Furthermore, a modified Airy-Heiskanen isostatic concept is applied that is enhanced by additional geophysical information in terms of a seismologically derived depth model of the Mohorovicic discontinuity, i.e., the boundary surface between the Earth’s crust and mantle. To counteract the increased computational demand of the more complex modeling, an efficient numerical algorithm is needed for the forward modeling. For space domain GFM, it has become more and more customary to use a mass discretization based on tesseroids, which are mass bodies bounded by geocentric spherical coordinate lines, and hence are directly linked to the curvature of the Earth. Several studies have demonstrated their superiority over classical prism methods with respect to precision and computation time. However, for global applications based on high-resolution DTMs, any computational speed-up with respect to a single mass body leads to a massive improvement in the overall computation time. This thesis presents a considerable optimization of previously used tesseroid formulas, where the gravitational field of a tesseroid and its derivatives up to second-order are represented in a compact and computationally attractive form. This allows an efficient numerical evaluation that reduces the overall runtime by about 20 to 55%, depending on the evaluated gravity field functional. Additionally, to correctly locate topographic masses in space, tesseroids are arranged on an ellipsoidal reference surface. Within this thesis, the novel tesseroid-based RWI approach is applied to different topographic input data and is used for various gravity field functionals in two main applications. Both are connected to ESA’s satellite mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) that measured the second-order derivatives of the gravitational potential, commonly known as gravity gradients. In the first application, RWI-based topographic-isostatic effects are calculated along the orbit of the GOCE satellite and are subtracted from the gravity gradient observations. In this way, the measurement signal is smoothed so that interpolation and prediction tasks, such as harmonic downward continuation of the gradients from satellite altitude to the Earth’s surface, can be executed with an improved numerical stability. While in previous studies such a concept was applied to simulated gravity gradients, this thesis presents the application to real GOCE measurements. As the smoothing effect strongly depends on the variability of the topography crossed by the satellite, this procedure is particularly suitable for regional applications. For a time series when the satellite passed the Himalayan region, a comparison of the observed gradients to the reduced ones reveals significant smoothing effects that are quantified by analyses in the space and frequency domain. The second application contributes to the task of height system unification, which aims to connect the different locally defined reference levels, conventionally used for national height systems. This is achieved by a satellite-based method which employs global geopotential models derived from data of the GOCE mission, whose limited spectral resolution is extended by high-frequency topographic effects of the RWI approach. To extract these high-frequency signals, a novel (residual) gravity forward modeling method is proposed that allows to perform the required high pass filtering directly in the gravity domain, thus, avoiding the above-mentioned assumption (iii) of the RTM method. By using three representative study areas in Germany, Austria, and Brazil, the benefit and importance of high-frequency topography-implied gravity signals for an accurate estimation of height datum offsets is demonstrated. As a highlight of this thesis, the RWI approach is utilized to generate a series of topographic-isostatic gravity field models. These RWI models provide a high-resolution representation of the Earth’s topographic-isostatic gravitational potential in terms of spherical harmonics expanded up to degree and order 1800 (Release 2012), and 2190 (Release 2015). The spherical harmonic coefficients of these models are obtained from a spherical harmonic analysis of global gridded potential values, which have been calculated by massive parallel computing on high-performance computer systems. By using spherical harmonic synthesis, the RWI model can be used to efficiently calculate various functionals of the topographic-isostatic potential in different heights. For this purpose, the RWI models are publicly available via the database of the International Centre for Global Earth Models (ICGEM) and have already been used in a wide range of studies by other research groups. Note de contenu : 1. Introductory chapter
2. Optimized formulas for the gravitational field of a tesseroid
3. A wavelet-based assessment of topographic-isostatic reductions for GOCE gravity gradients
4. The Rock-Water-Ice topographic gravity field model RWI TOPO 2015 and its comparison to a conventional rock-equivalent version
5. On high-frequency topography-implied gravity signals for height system unification 6. Height system unification based on the fixed GBVP approachNuméro de notice : 17488 Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : dissertation : : Karlsruhe Institute of Technology : 2017 En ligne : http://dx.doi.org/10.5445/KSP/1000068500 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89828 Documents numériques
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Gravity forward modeling ... - pdf éditeurAdobe Acrobat PDFGravité de la Terre : des mesures aux modèles, une image de la dynamique interne / Isabelle Panet (2015)
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