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Wavelet modeling of the gravity field over Japan / Isabelle Panet in Bulletin of the Geographical survey institute, vol 57 (December 2009)  

Public [article]  inBulletin of the Geographical survey institute > vol 57 (December 2009) . - pp 19 - 33 Titre : Wavelet modeling of the gravity field over Japan Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Yuki Kuroishi, Auteur ; Matthias Holschneider, Auteur Année de publication : 2009 Article en page(s) : pp 19 - 33 Note générale : Bibliographie 2e partie article : https://www.gsi.go.jp/common/000054750.pdf Langues : 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 ondelettes Résumé : (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 [article]

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