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Auteur Matthias Holschneider |
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Affiner la recherche Interroger des sources externesWavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations / M. Hayn in Geophysical journal international, vol 189 n° 3 (June 2012)
Titre : Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations Type de document : Article/Communication Auteurs : M. Hayn, Auteur ; Isabelle Panet Année de publication : 2012 Article en page(s) : pp 1430 - 1456 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] anomalie de pesanteur
[Termes IGN] données GRACE
[Termes IGN] manteau terrestre
[Termes IGN] modèle de géopotentiel
[Termes IGN] ondelette d'Abel-Poisson
[Termes IGN] Pacifique (océan)
[Termes IGN] subduction
[Termes IGN] transformation en ondelettesRésumé : (Auteur) In the eighties, the analysis of satellite altimetry data leads to the major discovery of gravity lineations in the oceans, with wavelengths between 200 and 1400 km. While the existence of the 200 km scale undulations is widely accepted, undulations at scales larger than 400 km are still a matter of debate. In this paper, we revisit the topic of the large‐scale geoid undulations over the oceans in the light of the satellite gravity data provided by the GRACE mission, considerably more precise than the altimetry data at wavelengths larger than 400 km.
First, we develop a dedicated method of directional Poisson wavelet analysis on the sphere with significance testing, in order to detect and characterize directional structures in geophysical data on the sphere at different spatial scales. This method is particularly well suited for potential field analysis. We validate it on a series of synthetic tests, and then apply it to analyze recent gravity models, as well as a bathymetry data set independent from gravity. Our analysis confirms the existence of gravity undulations at large scale in the oceans, with characteristic scales between 600 and 2000 km. Their direction correlates well with present‐day plate motion over the Pacific ocean, where they are particularly clear, and associated with a conjugate direction at 1500 km scale. A major finding is that the 2000 km scale geoid undulations dominate and had never been so clearly observed previously. This is due to the great precision of GRACE data at those wavelengths. Given the large scale of these undulations, they are most likely related to mantle processes. Taking into account observations and models from other geophysical information, as seismological tomography, convection and geochemical models and electrical conductivity in the mantle, we conceive that all these inputs indicate a directional fabric of the mantle flows at depth, reflecting how the history of subduction influences the organization of lower mantle upwellings.Numéro de notice : A2012-742 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2012.05455.x Date de publication en ligne : 19/04/2012 En ligne : https://doi.org/10.1111/j.1365-246X.2012.05455.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91491
in Geophysical journal international > vol 189 n° 3 (June 2012) . - pp 1430 - 1456[article]
Titre : Flexible dataset combination and modelling by domain decomposition approaches Type de document : Article/Communication Auteurs : Isabelle Panet Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 137 Projets : 2-Pas d'info accessible - article non ouvert / Conférence : IAG 2009, 7th Hotine-Marussi Symposium on Mathematical Geodesy 06/06/2009 10/06/2009 Rome Italie Proceedings Springer Importance : pp 67 - 73 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] compensation par moindres carrés
[Termes IGN] erreur systématique
[Termes IGN] filtrage du bruit
[Termes IGN] Japon
[Termes IGN] modèle de géopotentiel
[Termes IGN] modèle de géopotentiel local
[Termes IGN] ondelette
[Termes IGN] ondelette d'Abel-Poisson
[Termes IGN] transformation en ondelettesRésumé : (auteur) For geodetic and geophysical purposes, such as geoid determination or the study of the Earth’s structure, heterogeneous gravity datasets of various origins need to be combined over an area of interest, in order to derive a local gravity model at the highest possible resolution. The quality of the obtained gravity model strongly depends on the use of appropriate noise models for the different datasets in the combination process. In addition to random errors, those datasets are indeed often affected by systematic biases and correlated errors. Here we show how wavelets can be used to realize such combination in a flexible and economic way, and how the use of domain decomposition approaches allows to recalibrate the noise models in different wavebands and for different areas. We represent the gravity potential as a linear combination of Poisson multipole wavelets (Holschneider et al. 2003). We compute the wavelet model of the gravity field by regularized least-squares adjustment of the datasets. To solve the normal system, we apply the Schwarz iterative algorithms, based on a domain decomposition of the models space. Hierarchical scale subdomains are defined as subsets of wavelets at different scales, and for each scale, block subdomains are defined based on spatial splittings of the area. In the computation process, the data weights can be refined for each subdomain, allowing to take into account the effect of correlated noises in a simple way. Similarly, the weight of the regularization can be recalibrated for each subdomain, introducing non-stationarity in the a priori assumption of smoothness of the gravity field. We show and discuss examples of application of this method for regional gravity field modelling over a test area in Japan. Numéro de notice : C2009-035 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-22078-4_10 Date de publication en ligne : 18/11/2011 En ligne : https://doi.org/10.1007/978-3-642-22078-4_10 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91642 
Titre : Représentations en ondelettes du champ de pesanteur Type de document : Article/Communication Auteurs : Isabelle Panet Année de publication : 2011 Article en page(s) : pp 79 - 85 Note générale : Bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur local
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] géoïde terrestre
[Termes IGN] Japon
[Termes IGN] ondelette
[Termes IGN] surface de référence
[Termes IGN] variationRésumé : (Auteur) [introduction] La connaissance à haute résolution du champ de pesanteur et du géoïde, surface équipotentielle du champ qui se confond avec le niveau moyen des océans sans courants ni marées, est essentielle pour de nombreuses applications. La surface de référence des altitudes, qui permet la conversion des hauteurs mesurées par GPS en altitudes, est calculée à partir d’un modèle de géoïde. En mer, le géoïde est la surface de référence pour la détermination des courants marins. Enfin, la connaissance du champ de pesanteur et de ses variations temporelles renseigne sur la distribution des masses dans le système Terre. [...] Pour atteindre cet objectif, l’utilisation de représentations fonctionnelles du champ de pesanteur, à partir de fonctions localisées à la fois spatialement et spectralement, est très appropriée. Elle permet de combiner les mesures en leur affectant différentes pondérations dans les différentes bandes spectrales et spatiales. Dans cet article, nous présentons le principe de ces représentations et du calcul de modèles en ondelettes du champ de pesanteur terrestre, ainsi qu'un exemple d’application au calcul du champ de pesanteur sur le Japon. Numéro de notice : A2011-145 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtSansCL DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30924
in Bulletin d'information scientifique et technique de l'IGN > n° 77 (avril 2011) . - pp 79 - 85[article]Exemplaires(1)
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Titre : Wavelet modelling of the gravity field by domain decomposition methods: an example over Japan Type de document : Article/Communication Auteurs : Isabelle Panet Année de publication : 2011 Article en page(s) : pp 203 - 219 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse harmonique
[Termes IGN] bruit blanc
[Termes IGN] bruit rose
[Termes IGN] harmonique sphérique
[Termes IGN] itération
[Termes IGN] Japon
[Termes IGN] modèle de géopotentiel local
[Termes IGN] potentiel de pesanteur terrestre
[Termes IGN] transformation en ondelettesRésumé : (auteur) With the advent of satellite gravity, large gravity data sets of unprecedented quality at low and medium resolution become available. For local, high resolution field modelling, they need to be combined with the surface gravity data. Such models are then used for various applications, from the study of the Earth interior to the determination of oceanic currents. Here we show how to realize such a combination in a flexible way using spherical wavelets and applying a domain decomposition approach. This iterative method, based on the Schwarz algorithms, allows to split a large problem into smaller ones, and avoids the calculation of the entire normal system, which may be huge if high resolution is sought over wide areas. A subdomain is defined as the harmonic space spanned by a subset of the wavelet family. Based on the localization properties of the wavelets in space and frequency, we define hierarchical subdomains of wavelets at different scales. On each scale, blocks of subdomains are defined by using a tailored spatial splitting of the area. The data weighting and regularization are iteratively adjusted for the subdomains, which allows to handle heterogeneity in the data quality or the gravity variations. Different levels of approximations of the subdomains normals are also introduced, corresponding to building local averages of the data at different resolution levels. We first provide the theoretical background on domain decomposition methods. Then, we validate the method with synthetic data, considering two kinds of noise: white noise and coloured noise. We then apply the method to data over Japan, where we combine a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoid is obtained at about 15 km resolution and a corrector grid for the surface model is derived. Numéro de notice : A2011-604 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2010.04840.x Date de publication en ligne : 01/01/2011 En ligne : https://doi.org/10.1111/j.1365-246X.2010.04840.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91678
in Geophysical journal international > vol 184 n° 1 (January 2011) . - pp 203 - 219[article]Documents numériques
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Wavelet modelling of the gravity field .. - pdf éditeurAdobe Acrobat PDF
Titre : Wavelet modeling of the gravity field over Japan Type de document : Article/Communication Auteurs : Isabelle Panet Année de publication : 2009 Article en page(s) : pp 19 - 33 Note générale : Bibliographie
2e partie article : https://www.gsi.go.jp/common/000054750.pdfLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] bruit blanc
[Termes IGN] champ de pesanteur local
[Termes IGN] géoïde local
[Termes IGN] harmonique sphérique
[Termes IGN] Japon
[Termes IGN] levé gravimétrique
[Termes IGN] modèle de géopotentiel local
[Termes IGN] ondelette sphérique
[Termes IGN] transformation en ondelettesRésumé : (Auteur) Knowing the geoïd over Japan is essential for many geodetical and geophysical applications. Because of the tectonic settings of the area, significant geoid undulations occur in a wide range of spatial scales and make the determination of the geoïd a complex task. In some applications, high absolute accuracy at long and medium wavelengths is required for geoïd models with high resolution, which can be achieved by a proper combination of satellite gravity information with densely-distributed surface gravity data after careful consideration of their respective error characteristics. Here we show how to realize such a combination in a flexible way using spherical wavelets. The gravity potential is expressed as a linear combination of wavelets, whose coefficients are obtained by a least squares adjustment of the datasets. The combination needs to handle a large system of equations and we apply a domain decomposition method. First, we define sub-domains as subsets of wavelets. Based on the localization properties of the wavelets in space and frequency, we define hierarchical sub-domains of wavelets at different scales. On each scale, blocks of sub-domains are defined by using a tailored spatial splitting of the area. Second, we approximate the normal matrix for each block by introducing local approximation of the wavelets depending on the scale, in which local averages of the data are actually used for computation. Finally, we solve the system iteratively. In the beginning we validate the method with synthetic data, considering two kinds of noise: white noise and colored noise. We then apply the method to data over Japan: a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoïd is obtained at about 15 km resolution and the residuals indicate the existence of possible biases in the surface model. This information is used to correct the local model and the method is repeated with the corrected data, resulting in an improved hybrid model of the gravity field over Japan. Copyright Geographical Survey Institute Numéro de notice : A2009-558 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans En ligne : https://www.gsi.go.jp/common/000054749.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30187
in Bulletin of the Geographical survey institute > vol 57 (December 2009) . - pp 19 - 33[article]Exemplaires(1)
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