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Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates / Tobias Nilsson in Journal of geodesy, vol 91 n° 7 (July 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 7 (July 2017) . - pp 857 - 866 Titre : Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates Type de document : Article/Communication Auteurs : Tobias Nilsson, Auteur ; Benedikt Soja, Auteur ; Kyriakos Balidakis, Auteur ; Maria Karbon, Auteur ; Robert Heinkelmann, Auteur ; Zhiguo Deng, Auteur ; Harald Schuh, Auteur Année de publication : 2017 Article en page(s) : pp 857 - 866 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse de données [Termes IGN] filtre de Kalman [Termes IGN] gradient de troposphère [Termes IGN] interférométrie à très grande base [Termes IGN] longueur du jour [Termes IGN] modèle atmosphérique [Termes IGN] retard troposphérique zénithal [Termes IGN] temps universel Résumé : (Auteur) The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external information on the zenith wet delays (ZWD) and tropospheric gradients from GPS or numerical weather prediction models is studied. Additionally, we test estimating tropospheric gradients in the data analysis, which is normally not done. To evaluate the results, we compared the UT1-UTC values from the Intensives to those from simultaneous 24-h VLBI session. Furthermore, we calculated length of day (LOD) estimates using the UT1-UTC values from consecutive Intensives and compared these to the LOD estimated by GPS. We find that there is not much benefit in using external ZWD; however, including external information on the gradients improves the agreement with the reference data. If gradients are estimated in the data analysis, and appropriate constraints are applied, the WRMS difference w.r.t. UT1-UTC from 24-h sessions is reduced by 5% and the WRMS difference w.r.t. the LOD from GPS by up to 12%. The best agreement between Intensives and the reference time series is obtained when using both external gradients from GPS and additionally estimating gradients in the data analysis. Numéro de notice : A2017-298 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0985-7 En ligne : http://doi.org/10.1007/s00190-016-0985-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85333 [article]

GRACE era variability in the Earth's oblateness: a comparison of estimates from six different sources / Thierry Meyrath in Geophysical journal international, vol 208 n° 2 (February 2017)  

Public [article]  inGeophysical journal international > vol 208 n° 2 (February 2017) . - pp 1126 - 1138 Titre : GRACE era variability in the Earth's oblateness: a comparison of estimates from six different sources Type de document : Article/Communication Auteurs : Thierry Meyrath, Auteur ; Paul Rebischung , Auteur ; Tonie M. van Dam, Auteur Année de publication : 2017 Projets : 1-Pas de projet / Article en page(s) : pp 1126 - 1138 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] données GRACE [Termes IGN] données TLS (télémétrie) [Termes IGN] gravimétrie spatiale [Termes IGN] longueur du jour [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] rotation de la Terre [Termes IGN] série temporelle Résumé : (auteur) We study fluctuations in the degree-2 zonal spherical harmonic coefficient of the Earth's gravity potential, C20, over the period 2003–2015. This coefficient is related to the Earth's oblateness and studying its temporal variations, ΔC20, can be used to monitor large-scale mass movements between high and low latitude regions. We examine ΔC20 inferred from six different sources, including satellite laser ranging (SLR), GRACE and global geophysical fluids models. We further include estimates that we derive from measured variations in the length-of-day (LOD), from the inversion of global crustal displacements as measured by GPS, as well as from the combination of GRACE and the output of an ocean model as described by Sun et al. We apply a sequence of trend and seasonal moving average filters to the different time-series in order to decompose them into an interannual, a seasonal and an intraseasonal component. We then perform a comparison analysis for each component, and we further estimate the noise level contained in the different series using an extended version of the three-cornered-hat method. For the seasonal component, we generally obtain a very good agreement between the different sources, and except for the LOD-derived series, we find that over 90 per cent of the variance in the seasonal components can be explained by the sum of an annual and semiannual oscillation of constant amplitudes and phases, indicating that the seasonal pattern is stable over the considered time period. High consistency between the different estimates is also observed for the intraseasonal component, except for the solution from GRACE, which is known to be affected by a strong tide-like alias with a period of about 161 d. Estimated interannual components from the different sources are generally in agreement with each other, although estimates from GRACE and LOD present some discrepancies. Slight deviations are further observed for the estimate from the geophysical models, likely to be related to the omission of polar ice and groundwater changes in the model combination we use. On the other hand, these processes do not seem to play an important role at seasonal and shorter timescales, as the sum of modelled atmospheric, oceanic and hydrological effects effectively explains the observed C20 variations at those scales. We generally obtain very good results for the solution from SLR, and we confirm that this well-established technique accurately tracks changes in C20. Good agreement is further observed for the estimate from the GPS inversion, showing that this indirect method is successful in capturing fluctuations in C20 on scales ranging from intra- to interannual. Obtaining accurate estimates from LOD, however, remains a challenging task and more reliable models of atmospheric wind fields are needed in order to obtain high-quality ΔC20, in particular at the seasonal scale. The combination of GRACE data and the output of an ocean model appears to be a promising approach, particularly since corresponding ΔC20 is not affected by tide-like aliases, and generally gives better results than the solution from GRACE, which still seems to be of rather poor quality. Numéro de notice : A2017-863 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggw441 Date de publication en ligne : 24/11/2016 En ligne : https://doi.org/10.1093/gji/ggw441 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89852 [article]

Proceedings of the IERS Workshop on Combination Research and Global Geophysical Fluids, Bavarian Academy of Sciences, Munich, Germany, 18 - 21 November 2002 / Bernd Richter (2003) 

Public Titre : Proceedings of the IERS Workshop on Combination Research and Global Geophysical Fluids, Bavarian Academy of Sciences, Munich, Germany, 18 - 21 November 2002 Type de document : Actes de congrès Auteurs : Bernd Richter, Éditeur scientifique ; W. Schwegmann, Éditeur scientifique ; Wolfgang R. Dick, Éditeur scientifique Editeur : Francfort sur le Main : Bundesamt für Kartographie und Geodäsie Année de publication : 2003 Collection : IERS Technical note, ISSN 1019-4568 num. 30 Conférence : IERS 2002, Workshop on Combination Research and Global Geophysical Fluids 18/11/2002 21/11/2002 Munich Allemagne OA Proceedings Importance : 235 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-89888-877-6 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur systématique [Termes IGN] longueur du jour [Termes IGN] mouvement du pôle [Termes IGN] orientation de la Terre [Termes IGN] repère de référence céleste [Termes IGN] rotation de la Terre [Termes IGN] vitesse Note de contenu : Introduction Towards a Rigorous Combination of Space Geodetic Techniques / M. Rothacher Combination Strategies and Issues for TRF / CRF / EOPs Ø Combination of Station Positions and Velocities / Z. Altamimi, C. Boucher, H. Drewes, R. Ferland, K. Larson, J. Ray, M. Rothacher Ø ITRS Center Views on Combination Issues / C. Boucher, Z. Altamimi Ø Remarks on Some Problems in the Combination of Station Coordinate and Velocity Solutions / H. Drewes, D. Angermann Ø TRF Combination at NRCan: Status Report / R. Ferland Ø Celestial Reference Frame Issues / J. Souchay, C. Ma, M. Feissel-Vernier Ø General Combination of EOP Series / D. Gambis, T. Johnson, R. Gross, J. Vondrak Ø EOP Alignment Campaign, IDS/IGS/ILRS/IVS EOP Combinations, Systematic Errors / A. Nothnagel, R. Dill, M. Feissel-Vernier, R. Ferland, R. Noomen, P. Willis Ø Consistency Analysis Between EOP Series and Reference Frames / D. Gambis, C. Bizouard Issues of a Rigorous Combination Ø Conventions and Combinations / D. D. McCarthy, G. Petit Ø Impact of IAU Resolutions on Earth Rotation Parameters / N. Capitaine, D. D. McCarthy Ø Issues of a Rigorous Combination / J. Ray, S. Y. Zhu Ø Combination of Multi-Satellite Techniques at the Observation Level / S. Zhu, Ch. Reigber, F.-H. Massmann, H. Neumayer, H. Meixner, F. Flechtner Ø On Systematic Differences in Individual Solutions and IERS Products / Z. Malkin Ø Numerical Aspects of Combination at the Observation Equation and Normal Equation Level / M. Gerstl Ø IERS SINEX Combination Campaign / D. Angermann, D. Thaller, M. Rothacher Ø Multi-technique Combination of Time Series of Station Positions and Earth Orientation Parameters / Z. Altamimi, C. Boucher Ø Combination of Loosely Constrained Solutions / G. Bianco, R. Devoti, V. Luceri Ø IERS SINEX Combination Campaign: First Results at NRCan / R. Ferland Ø Rank Defect Analysis and Variance Component Estimation for Inter-Technique Combination / R. Kelm Global Geophysical Fluids Ø The Global Geophysical Fluids Center (GGFC) of the International Earth Rotation and Reference Systems Service / B. F. Chao, V. Dehant, R. S. Gross, H.-P. Plag, R. D. Ray, D. A. Salstein, T. van Dam, T. van Hoolst, M. M. Watkins, C. R. Wilson Ø The GGFC Special Bureau for the Atmosphere of the International Earth Rotation and Reference Systems Service / D. A. Salstein Ø Reliability of Atmospheric Torque for Geodesy / O. de Viron, V. Dehant Ø Time Variable Atmospheric and Oceanic Signals in Excitation Functions of Polar Motion / J. Nastula, D. A. Salstein, B. Koaczek Ø The GGFC Special Bureau for the Oceans: Past Progress and Future Plans / R. S. Gross Ø Comparison of Oceanographic Signals with SLR-Derived Gravity Observations / C. M. Cox, A. Au, J.-P. Boy, B. Chao Ø Oceanic Excitation of Polar Motion and Nutation: An Overview / A. Brzezinski Ø Possible Role of the Oceans in the Variations of Length of Day at High Frequencies / T. J. Johnson Ø The Hydrology Bureau of the Global Geophysical Fluids Center / C. R. Wilson, J. Chen Ø Time Variable Gravity Field: Using Future Earth Observation Missions for High Frequency De-Aliasing / T. Gruber, T. Peters Ø GGFC Special Bureau for Tides / R. Ray Ø Recent Work on Theoretical Modeling of Nutation / J. M. Ferrándiz, A. Escapa, J. F. Navarro, J. Getino Ø GGFC Special Bureau for the Core / T. Van Hoolst, V. Dehant, W. Kuang Ø GGFC Special Bureau for Loading: Current Status and Plans / T. Van Dam, H.-P. Plag, O. Francis, P. Gegout Posters Ø Time Series of Site Positions and Datum Parameters / D. Angermann, B. Meisel, M. Krügel, H. Müller, V. Tesmer Ø IVS Pilot Project Tropospheric Parameters / J. Boehm, H. Schuh Ø SINEX File Implementation in the VLBI Calc/Solve Analysis System / C. Ma, L. Petrov Ø Some Problems in the IERS Products from User's Point of View / Z. Malkin Ø Comparison and Combination of the Earth Orientation Parameters Submitted to the IERS Alignment >Campaign 2002 / E. Messerer, J. Boehm, H. Schuh Ø Combination of Terrestrial Reference Frames and ERP at University of Newcastle / K. Nurutdinov, P. J. Clarke, Ph. Moore Ø Determination of Station Coordinates and EOP from Combination of Different Techniques / J. Kosteleck, I. Peek Ø Electromagnetic Core-Mantle Coupling / S. Ponsar, V. Dehant, T. Van Hoolst Ø Environmental Loadings: Effects on Height and Gravity / S. Zerbini, C. Romagnoli, L. Lago, B. Richter, D. Simon Ø IDS Analysis Campaign: current combination activity / J. J. Valette, L. Soudarin, Z. Altamimi Conclusions Ø Recommendations and Action Items Numéro de notice : 14603 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Actes Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=34673

Contient

• Combination of Station Positions and Velocities / Zuheir Altamimi (2003)  
• ITRS Center Views on Combination Issues / Claude Boucher (2003)  
• EOP Alignment Campaign, IDS/IGS/ILRS/IVS EOP Combinations, Systematic Errors / Axel Nothnagel (2003)  
• Celestial Reference Frame Issues / Jean Souchay (2003)  
• Multi-technique combination of time series of station positions and Earth orientation parameters / Zuheir Altamimi (2003)  
• IDS Analysis Campaign: current combination activity / Jean-Jacques Valette (2003)  

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Documents numériques

en open access 14603_iers_tn30_richter.pdf Adobe Acrobat PDF

La rotation de la Terre / R. Abarca Del Rio (1997)

Public Titre : La rotation de la Terre : Etude du cycle annuel et de la variabilité basse fréquence. Etude climatique de la rotation terrestre Type de document : Thèse/HDR Auteurs : R. Abarca Del Rio, Auteur ; Anny Cazenave, Directeur de thèse Editeur : Toulouse : Université de Toulouse 3 Paul Sabatier Année de publication : 1997 Importance : 241 p. Format : 21 x 30 cm Note générale : Bibliographie Thèse présentée pour l'obtention du diplôme de doctorat de l'université Paul Sabatier, spécialité géophysique Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] climat terrestre [Termes IGN] longueur du jour [Termes IGN] mouvement du pôle [Termes IGN] rotation de la Terre [Termes IGN] variation Index. décimale : THESE Thèses et HDR Numéro de notice : 27387 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse française Note de thèse : Thèse de doctorat : Spécialité géophysique : Toulouse 3 : 1997 nature-HAL : Thèse DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=45391

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
27387-01	THESE	Livre	Centre de documentation	Thèses	Disponible