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Basic equations for constructing geopotential models from the gravitational potential derivatives of the first and second orders in the terrestrial reference frame / M. Petrovskaya in Journal of geodesy, vol 86 n° 7 (July 2012)
[article]
Titre : Basic equations for constructing geopotential models from the gravitational potential derivatives of the first and second orders in the terrestrial reference frame Type de document : Article/Communication Auteurs : M. Petrovskaya, Auteur ; A. Vershkov, Auteur Année de publication : 2012 Article en page(s) : pp 521 - 530 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] gradient de gravitation
[Termes IGN] harmonique sphérique
[Termes IGN] modèle de géopotentiel
[Termes IGN] repère de référence
[Termes IGN] système de référence mondialRésumé : (Auteur) This research represents a continuation of the investigation carried out in the paper of Petrovskaya and Vershkov (J Geod 84(3):165–178, 2010) where conventional spherical harmonic series are constructed for arbitrary order derivatives of the Earth gravitational potential in the terrestrial reference frame. The problem of converting the potential derivatives of the first and second orders into geopotential models is studied. Two kinds of basic equations for solving this problem are derived. The equations of the first kind represent new non-singular non-orthogonal series for the geopotential derivatives, which are constructed by means of transforming the intermediate expressions for these derivatives from the above-mentioned paper. In contrast to the spherical harmonic expansions, these alternative series directly depend on the geopotential coefficients Cn,m and Sn,m . Each term of the series for the first-order derivatives is represented by a sum of these coefficients, which are multiplied by linear combinations of at most two spherical harmonics. For the second-order derivatives, the geopotential coefficients are multiplied by linear combinations of at most three spherical harmonics. As compared to existing non-singular expressions for the geopotential derivatives, the new expressions have a more simple structure. They depend only on the conventional spherical harmonics and do not depend on the first- and second-order derivatives of the associated Legendre functions. The basic equations of the second kind are inferred from the linear equations, constructed in the cited paper, which express the coefficients of the spherical harmonic series for the first- and second-order derivatives in terms of the geopotential coefficients. These equations are converted into recurrent relations from which the coefficients Cn,m and Sn,m are determined on the basis of the spherical harmonic coefficients of each derivative. The latter coefficients can be estimated from the values of the geopotential derivatives by the quadrature formulas or the least-squares approach. The new expressions of two kinds can be applied for spherical harmonic synthesis and analysis. In particular, they might be incorporated in geopotential modeling on the basis of the orbit data from the CHAMP, GRACE and GOCE missions, and the gradiometry data from the GOCE mission. Numéro de notice : A2012-356 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0535-2 Date de publication en ligne : 31/12/2011 En ligne : https://doi.org/10.1007/s00190-011-0535-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31802
in Journal of geodesy > vol 86 n° 7 (July 2012) . - pp 521 - 530[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012071 RAB Revue Centre de documentation En réserve L003 Disponible Separation of global time-variable gravity signals into maximally independent components / E. Forootan in Journal of geodesy, vol 86 n° 7 (July 2012)
[article]
Titre : Separation of global time-variable gravity signals into maximally independent components Type de document : Article/Communication Auteurs : E. Forootan, Auteur ; J. Kusche, Auteur Année de publication : 2012 Article en page(s) : pp 477 - 497 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse en composantes indépendantes
[Termes IGN] analyse en composantes principales
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données GRACE
[Termes IGN] filtrage du signal
[Termes IGN] traitement de donnéesRésumé : (Auteur) The Gravity Recovery and Climate Experiment (GRACE) products provide valuable information about total water storage variations over the whole globe. Since GRACE detects mass variations integrated over vertical columns, it is desirable to separate its total water storage anomalies into their original sources. Among the statistical approaches, the principal component analysis (PCA) method and its extensions have been frequently proposed to decompose the GRACE products into space and time components. However, these methods only search for decorrelated components that on the one hand are not always interpretable and on the other hand often contain a superposition of independent source signals. In contrast, independent component analysis (ICA) represents a technique that separates components based on assumed statistical independence using higher-order statistical information. If one assumes that independent physical processes generate statistically independent signal components added up in the GRACE observations, separating them by ICA is a reliable strategy to identify these processes. In this paper, the performance of the conventional PCA, its rotated extension and ICA are investigated when applied to the GRACE-derived total water storage variations. These analyses have been tested on both a synthetic example and on the real GRACE level-2 monthly solutions derived from GeoForschungsZentrum Potsdam (GFZ RL04) and Bonn University (ITG2010). Within the synthetic example, we can show how imposing statistical independence in the framework of ICA improves the extraction of the ‘original’ signals from a GRACE-type superposition. We are therefore confident that also for the real case the ICA algorithm, without making prior assumptions about the long-term behaviour or on the frequencies contained in the signal, improves over the performance of PCA and its rotated extension in the separation of periodical and long-term components. Numéro de notice : A2012-355 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0532-5 Date de publication en ligne : 22/11/2011 En ligne : https://doi.org/10.1007/s00190-011-0532-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31801
in Journal of geodesy > vol 86 n° 7 (July 2012) . - pp 477 - 497[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012071 RAB Revue Centre de documentation En réserve L003 Disponible Choix d'un modèle géopotentiel global pour la détermination du géoïde en Algérie / N. Rabehi in Bulletin des sciences géographiques, n° 27 (juin 2012)
[article]
Titre : Choix d'un modèle géopotentiel global pour la détermination du géoïde en Algérie Type de document : Article/Communication Auteurs : N. Rabehi, Auteur ; M. Kreri, Auteur ; M. Touabet, Auteur ; M. Terbeche, Auteur Année de publication : 2012 Article en page(s) : pp 33 - 39 Note générale : Bibliographie Langues : Anglais (eng) Français (fre) Arabe (ara) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Algérie
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données CHAMP
[Termes IGN] données GRACE
[Termes IGN] géoïde localRésumé : (Auteur) La connaissance de nouveaux modèles de champ de pesanteur a été améliorée durant les dernières années à partir des nouvelles missions spatiales (CHAMP et GRACE) dédiées à la détermination précise de haute résolution du champ de pesanteur terrestre. Le problème du choix d'un modèle géopotentiel qui ajuste au mieux les données gravimétriques reste posé et demeure sujet à débat. Dans ce travail, nous apportons une contribution à l'étude du géoïde en Algérie en utilisant une méthode de filtrage des coefficients des modèles géopotentiels. Cette technique va nous conduire à connaître l'apport des nouveaux coefficients des modèles géopotentiels sur la détermination du géoïde en Algérie, en combinant les informations provenant du modèle géopotentiel choisi par la méthode de filtrage, des données gravimétriques terrestres (EOL) et éventuellement du modèle numérique du terrain (GTOPO30). Numéro de notice : A2012-499 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31945
in Bulletin des sciences géographiques > n° 27 (juin 2012) . - pp 33 - 39[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 253-2012011 RAB Revue Centre de documentation En réserve L003 Disponible Estimation of the zero-height geopotential level WoLVD in a local vertical datum from inversion of co-located GPS, leveling and geoid heights: a case study in the Hellenic islands / Christopher Kotsakis in Journal of geodesy, vol 86 n° 6 (June 2012)
[article]
Titre : Estimation of the zero-height geopotential level WoLVD in a local vertical datum from inversion of co-located GPS, leveling and geoid heights: a case study in the Hellenic islands Type de document : Article/Communication Auteurs : Christopher Kotsakis, Auteur ; K. Katsambalos, Auteur ; Dimitrios Ampatzidis, Auteur Année de publication : 2012 Article en page(s) : pp 423 - 439 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] Egée, mer
[Termes IGN] Grèce
[Termes IGN] modèle de géopotentiel local
[Termes IGN] niveau moyen des mers
[Termes IGN] réseau altimétrique local
[Termes IGN] zéro hydrographiqueRésumé : (Auteur) The estimation of the zero-height geopotential level of a local vertical datum (LVD) is a key task towards the connection of isolated physical height frames and their unification into a common vertical reference system. Such an estimate resolves, in principle, the ‘ambiguity’ of a traditional crust-fixed LVD by linking it with a particular equipotential surface of Earth’s gravity field under the presence of an external geopotential model. The aim of this paper is to study the estimation scheme that can be followed for solving the aforementioned problem based on the joint inversion of co-located GPS and leveling heights in conjunction with a fixed Earth gravity field model. Several case studies with real data are also presented that provide, for the first time, precise estimates of the LVD offsets for a number of Hellenic islands across the Aegean and Ionian Sea. Numéro de notice : A2012-244 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0530-7 Date de publication en ligne : 03/12/2011 En ligne : https://doi.org/10.1007/s00190-011-0530-7 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31690
in Journal of geodesy > vol 86 n° 6 (June 2012) . - pp 423 - 439[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2012061 RAB Revue Centre de documentation En réserve L003 Disponible Simulation study of a follow-on gravity mission to GRACE / B. Loomis in Journal of geodesy, vol 86 n° 5 (May 2012)
[article]
Titre : Simulation study of a follow-on gravity mission to GRACE Type de document : Article/Communication Auteurs : B. Loomis, Auteur ; R. Nerem, Auteur ; Scott B. Luthcke, Auteur Année de publication : 2012 Article en page(s) : pp 319 - 335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] crénelage
[Termes IGN] données GRACE
[Termes IGN] masse de la Terre
[Termes IGN] simulationRésumé : (Auteur) The gravity recovery and climate experiment (GRACE) has been providing monthly estimates of the Earth’s time-variable gravity field since its launch in March 2002. The GRACE gravity estimates are used to study temporal mass variations on global and regional scales, which are largely caused by a redistribution of water mass in the Earth system. The accuracy of the GRACE gravity fields are primarily limited by the satellite-to-satellite range-rate measurement noise, accelerometer errors, attitude errors, orbit errors, and temporal aliasing caused by un-modeled high-frequency variations in the gravity signal. Recent work by Ball Aerospace & Technologies Corp., Boulder, CO has resulted in the successful development of an interferometric laser ranging system to specifically address the limitations of the K-band microwave ranging system that provides the satellite-to-satellite measurements for the GRACE mission. Full numerical simulations are performed for several possible configurations of a GRACE Follow-On (GFO) mission to determine if a future satellite gravity recovery mission equipped with a laser ranging system will provide better estimates of time-variable gravity, thus benefiting many areas of Earth systems research. The laser ranging system improves the range-rate measurement precision to ~0.6 nm/s as compared to ~0.2 ?m/s for the GRACE K-band microwave ranging instrument. Four different mission scenarios are simulated to investigate the effect of the better instrument at two different altitudes. The first pair of simulated missions is flown at GRACE altitude (~480 km) assuming on-board accelerometers with the same noise characteristics as those currently used for GRACE. The second pair of missions is flown at an altitude of ~250 km which requires a drag-free system to prevent satellite re-entry. In addition to allowing a lower satellite altitude, the drag-free system also reduces the errors associated with the accelerometer. All simulated mission scenarios assume a two satellite co-orbiting pair similar to GRACE in a near-polar, near-circular orbit. A method for local time variable gravity recovery through mass concentration blocks (mascons) is used to form simulated gravity estimates for Greenland and the Amazon region for three GFO configurations and GRACE. Simulation results show that the increased precision of the laser does not improve gravity estimation when flown with on-board accelerometers at the same altitude and spacecraft separation as GRACE, even when time-varying background models are not included. This study also shows that only modest improvement is realized for the best-case scenario (laser, low-altitude, drag-free) as compared to GRACE due to temporal aliasing errors. These errors are caused by high-frequency variations in the hydrology signal and imperfections in the atmospheric, oceanographic, and tidal models which are used to remove unwanted signal. This work concludes that applying the updated technologies alone will not immediately advance the accuracy of the gravity estimates. If the scientific objectives of a GFO mission require more accurate gravity estimates, then future work should focus on improvements in the geophysical models, and ways in which the mission design or data processing could reduce the effects of temporal aliasing. Numéro de notice : A2012-241 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0521-8 Date de publication en ligne : 28/10/2011 En ligne : https://doi.org/10.1007/s00190-011-0521-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31687
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