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Flexible dataset combination and modelling by domain decomposition approaches / Isabelle Panet (2012)  

Public Titre : Flexible dataset combination and modelling by domain decomposition approaches Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Yuki Kuroishi, Auteur ; Matthias Holschneider, Auteur 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 ondelettes Résumé : (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

Ocean Loading in Brittany, Northwest France: Impact of the GPS Analysis Strategy / Joëlle Nicolas (2012)  

Public Titre : Ocean Loading in Brittany, Northwest France: Impact of the GPS Analysis Strategy Type de document : Article/Communication Auteurs : Joëlle Nicolas, Auteur ; Stéphane Durand, Auteur ; Mathilde Vergnolle, Auteur ; Laurent Morel, Auteur ; Stavros A. Melachroinos, Auteur ; Marie-Noëlle Bouin , Auteur ; François Fund, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 137 Conférence : IAG 2009, 7th Hotine-Marussi Symposium on Mathematical Geodesy 06/06/2009 10/06/2009 Rome Italie Proceedings Springer Importance : pp 367 - 372 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] Bernese [Termes IGN] GAMIT [Termes IGN] GINS [Termes IGN] GIPSY-OASIS [Termes IGN] surcharge océanique Résumé : (auteur) In this contribution, we analyze the impact of different GPS processing strategies on ocean tide loading estimation. We use continuous GPS data acquired during a 4-month campaign performed in 2004 in Brittany, Northwest France. Since the expected geodynamical signal in the estimated positions is exceeding the typical GPS data analysis noise, this data set can be used to compare the results obtained with different analysis software packages. Moreover, in this specific case we need short sub-daily solutions to study short-period signals instead of classical 24 h-solutions. The GPS capability for measuring 3D ocean tide loading deformation has already been assessed, but since we are looking for the finest signal as the one induced by the shallow water constituents, it is essential to be sure that the position time series represent a geodynamical signal and are not biased by the data processing strategy used. To analyze the possible effect of the methodology used on the geodynamical results, we compare different solutions computed with different strategies (Double Differencing and Precise Point Positioning) with various GPS analysis software packages (Bernese, GAMIT, GINS, and GIPSY/OASIS). We show that the different solution consistency is at the level of 1–3 mm. We also show that the data processing strategy has a mean effect of about 10–20% of the ocean tide loading signal amplitude. Numéro de notice : C2009-001 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-22078-4_55 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/978-3-642-22078-4_55 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102737

The choice of reference system in ITRF formulation / Zuheir Altamimi (2012)  

Public Titre : The choice of reference system in ITRF formulation Type de document : Article/Communication Auteurs : Zuheir Altamimi , Auteur ; Athanasios Dermanis, Auteur Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2012 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 137 Conférence : IAG 2009, 7th Hotine-Marussi Symposium on Mathematical Geodesy 06/06/2009 10/06/2009 Rome Italie Proceedings Springer Importance : pp 329 - 334 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] barycentre [Termes IGN] coordonnées cartésiennes géocentriques [Termes IGN] International Terrestrial Reference Frame [Termes IGN] moment cinétique [Termes IGN] système de référence géodésique [Termes IGN] vitesse Résumé : (auteur) The problem of choosing an optimal reference system for the International Terrestrial Reference Frame (ITRF) is studied for both the rigorous solution which is a simultaneous stacking (removal of the reference system at each data epoch and implementation of a linear in time coordinate model) for all techniques, as well as for the usual numerically convenient separation into a set of individual stackings one for each technique and a final combination step for the derived initial coordinates and velocities. Two approaches are followed, an algebraic and a kinematic one. The algebraic approach implements the inner constraints, which minimize the sum of squares of the unknown parameters, as well as partial inner constraints, which minimize the sum of squares of a subset of the unknown parameters. In the kinematical approach the optimal minimal constraints are derived by requiring the minimization of the apparent coordinate variations: (a) with respect to the origin by imposing constant coordinates for the network barycenter, (b) with respect to orientation by imposing zero relative angular momentum for the network points conceived as mass points with equal mass and (c) with respect to the scale by imposing constant mean quadratic size (involving the distances of stations from their barycenter). Numéro de notice : C2009-036 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1007/978-3-642-22078-4_49 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/978-3-642-22078-4_49 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91643