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Titre : Observing our changing Earth Type de document : Actes de congrès Auteurs : Michael G. Sideris, Éditeur scientifique Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2009 Collection : International Association of Geodesy Symposia, ISSN 0939-9585 num. 133 ISBN/ISSN/EAN : 978-3-540-85425-8 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] Global Geodetic Observing System
[Termes IGN] repère de référence
[Termes IGN] rotation de la TerreNote de contenu : Symposium GS001 Reference Frames
Symposium GS002 Gravity Field
Symposium GS003 Earth Rotation and Geodynamics
Symposium GS004 Positioning and Applications
Symposium GS005 The Global Geodetic Observing System (GGOS)Numéro de notice : 17530 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Actes nature-HAL : DirectOuvrColl/Actes DOI : 10.1007/978-3-540-85426-5 En ligne : https://doi.org/10.1007/978-3-540-85426-5 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90691 Optima multi-step collocation: application to the space-wise approach for GOCE data analysis / M. Reguzzoni in Journal of geodesy, vol 83 n° 1 (January 2009)
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Titre : Optima multi-step collocation: application to the space-wise approach for GOCE data analysis Type de document : Article/Communication Auteurs : M. Reguzzoni, Auteur ; N. Tselfes, Auteur Année de publication : 2009 Article en page(s) : pp 13 - 29 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse harmonique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] coefficient de géopotentiel
[Termes IGN] collocation
[Termes IGN] GOCE
[Termes IGN] harmonique sphérique
[Termes IGN] levé gravimétriqueRésumé : (Auteur) Collocation is widely used in physical geodesy. Its application requires to solve systems with a dimension equal to the number of observations, causing numerical problems when many observations are available. To overcome this drawback, tailored step-wise techniques are usually applied. An example of these step-wise techniques is the space-wise approach to the GOCE mission data processing. The original idea of this approach was to implement a two-step procedure, which consists of first predicting gridded values at satellite altitude by collocation and then deriving the geo-potential spherical harmonic coefficients by numerical integration. The idea was generalized to a multi-step iterative procedure by introducing a time-wise Wiener filter to reduce the highly correlated observation noise. Recent studies have shown how to optimize the original two-step procedure, while the theoretical optimization of the full multi-step procedure is investigated in this work. An iterative operator is derived so that the final estimated spherical harmonic coefficients are optimal with respect to the Wiener–Kolmogorov principle, as if they were estimated by a direct collocation. The logical scheme used to derive this optimal operator can be applied not only in the case of the space-wise approach but, in general, for any case of step-wise collocation. Several numerical tests based on simulated realistic GOCE data are performed. The results show that adding a pre-processing time-wise filter to the two-step procedure of data gridding and spherical harmonic analysis is useful, in the sense that the accuracy of the estimated geo-potential coefficients is improved. This happens because, in its practical implementation, the gridding is made by collocation over local patches of data, while the observation noise has a time-correlation so long that it cannot be treated inside the patch size. Therefore, the multi-step operator, which is in theory equivalent to the two-step operator and to the direct collocation, is in practice superior thanks to the time-wise filter that reduces the noise correlation before the gridding. The criteria for the choice of this filter are investigated numerically. Copyright Springer Numéro de notice : A2009-179 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0225-x En ligne : https://doi.org/10.1007/s00190-008-0225-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29809
in Journal of geodesy > vol 83 n° 1 (January 2009) . - pp 13 - 29[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-09011 RAB Revue Centre de documentation En réserve L003 Disponible 266-09012 RAB Revue Centre de documentation En réserve L003 Disponible Physically consistent system model for the study of the Earth's rotation, surface deformation and gravity field parameters / A. Hense (2009)
Titre : Physically consistent system model for the study of the Earth's rotation, surface deformation and gravity field parameters : scientific results of the DFG project Type de document : Monographie Auteurs : A. Hense, Auteur ; J. Sündermann, Auteur ; Hermann Drewes, Auteur ; et al., Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2009 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 317 Importance : 53 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8596-1 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] circulation atmosphérique
[Termes IGN] circulation océanique
[Termes IGN] déformation de la croute terrestre
[Termes IGN] modèle hydrographique
[Termes IGN] modèle physique
[Termes IGN] pesanteur terrestre
[Termes IGN] rotation de la Terre
[Termes IGN] surcharge océanique
[Termes IGN] terme de ChandlerIndex. décimale : 30.40 Géodésie physique Résumé : (Auteur) [introduction] This report is the final report of a serie of projects which studied the Earth's rotational parameters angular momentum, tensor of inertia as well as related variables of the Earth's gravitational field. A system view has been taken by trying to incorporate the contributions from the various subsystems of the Earth system in a physically consistent way. This introduction will highlight the project history and performance since 1996 and the state of the art in 2000. Note de contenu : 1. Introduction
1.1 The projects
1.2 Historical overview and motivations
2. Models of subsystems
2.1 Atmosphere models ECHAM
2.1.1 ECHAM5
2.1.2 Stand-alone atmosphere 20th century simulation
2.1.3 Results
2.2 Ocean model OMCT
2.3 Hydrological Discharge Model HDM
2.3.1 Continental hydrology modelling
2.3.1.1 SLS model component
2.3.1.2 HDM model component
2.3.1.3 Atmospheric forcing data
2.3.2 Results
2.3.2.1 Implementation of a 3-D relief model
2.3.2.2 Calculation of gravity field coefficients
2.3.2.3 Test simulations and validation of continental discharge with ECHAM4 and NCEP
2.3.2.4 Verification of simulated continental runoff (control runs)
2.3.2.5 Interface adaptation and verification of mass conservation at the boundaries in the coupled model system
2.3.2.6 Validation and analysis of continental water mass transports of ECOCTH
2.3.2.7 Statistical analysis and validation of simulated gravity field variations
2.3.2.8 Global water balance
2.3.3 Summary
3. Models of the coupled system
3.1 Coupled atmosphere-hydrosphere model ECOCTH
3.1.1 Model description
3.1.2 Validation
3.1.2.1 The lunisolar ocean tides
3.1.2.2 Global ocean circulation
3.1.2.3 Tropical variability and global warming
3.1.3 Results
3.1.3.1 Inter-annual variations and secular trends in length of day
3.2 Dynamic model of Earth rotation, gravity and surface deformation DyMEG
3.2.1 Numerical solution of the Liouville differential equation
3.2.2 Inverse model for surface deformations of the solid Earth due to mass loads
4. Results for Earth rotation, surface deformation and gravity
4.1 Validation of DyMEG with NCEP and ECCO
4.2 Results of DyMEG with ECOCTH forcing
5. Scientific highlights
5.1 Tidal mixing
5.1.1 Tidal mixing in OMCT2
5.1.2 Effect of tidal mixing on ocean water mass properties
5.2 Secular and decadal variations
5.2.1 Coupled simulation of Earth Rotation Parameters
5.2.2 Axial AAM long-term trends in 21st century scenario runs
5.3 Forcing mechanisms of the Chandler oscillation
5.3.1 Atmospheric and hydrospheric excitation of the Chandler oscillation
5.3.2 Noise as excitation mechanism of the Chandler oscillation
6. Conclusions and outlook
7. ReferencesNuméro de notice : 15454 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62723 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 15454-01 30.40 Livre Centre de documentation Géodésie Disponible Rapport du directeur sur l'activité et la gestion du Bureau international des poids et mesures (BIPM), 1er juillet 2008 - 30 juin 2009 / Bureau international des poids et mesures (2009)
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Titre : Rapport du directeur sur l'activité et la gestion du Bureau international des poids et mesures (BIPM), 1er juillet 2008 - 30 juin 2009 Titre original : Director's report on the activity and management of the International bureau of weights and measures (BIPM), 1 july 2008 - 30 june 2009 Type de document : Rapport Auteurs : Bureau international des poids et mesures , Auteur
Editeur : Sèvres : Bureau International des Poids et Mesures BIPM Année de publication : 2009 Collection : Rapport du directeur sur l'activité et la gestion du BIPM, ISSN 1606-3740 num. 10 Importance : 320 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-92-822-2235-5 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Métrologie
[Termes IGN] chimie
[Termes IGN] électricité
[Termes IGN] gravimétrie
[Termes IGN] masse
[Termes IGN] radiométrie
[Termes IGN] rayonnement ionisant
[Termes IGN] temps de propagation
[Termes IGN] thermométrieNote de contenu : 1 - Introduction
2 - Masse
3 - Temps, fréquences et gravimétrie
4 - Electricité
5 - Rayonnements ionisants
6 - Chimie
7 - Balance du watt
8 - La base de données du BIPM sur les comparaisons clés, KCDB
9 - Le Comité mixte des organisations régionales de métrologie et du BIPM, JCRB
10 - Publications et informatique
11 - Réunions et exposés au BIPM
12 - Certificats et Notes d'étude
13 - Finance, administration et services généraux
14 - Secrétariat
15 - Atelier de mécanique et entretien du siteNuméro de notice : 10653 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport d'activité En ligne : https://www.bipm.org/documents/20126/41865219/DIR2009-FR.pdf/ Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=39845
Titre : Regional gravity field modeling using airborne gravimetry data Type de document : Thèse/HDR Auteurs : Bas Alberts, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2009 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 70 Importance : 180 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-312-9 Note générale : Bibliographie
Document en téléchargement sur le site de NCG : lien dans la noticeLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur local
[Termes IGN] Chili
[Termes IGN] espace de Hilbert
[Termes IGN] gravimétrie aérienne
[Termes IGN] gravimétrie en mer
[Termes IGN] levé gravimétrique
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle de géopotentiel local
[Termes IGN] Nord, mer du
[Termes IGN] Ontario (Canada)
[Termes IGN] pondération
[Termes IGN] processus
[Termes IGN] traitement automatique de donnéesIndex. décimale : 30.42 Gravimétrie Résumé : (Auteur) Airborne gravimetry is the most efficient technique to provide accurate high-resolution gravity data in regions that lack good data coverage and that are difficult to access otherwise. With current airborne gravimetry systems gravity can be obtained at a spatial resolution of 2 km with an accuracy of 1-2' mGal. It is therefore an ideal technique to complement ongoing satellite gravity missions and establish the basis for many applications of regional gravity field modelling.
Gravity field determination using airborne gravity data can be divided in two major steps. The first step comprises the preprocessing of raw in-flight gravity sensor measurements to obtain gravity disturbances at flight level and the second step consists of the inversion of these observations into gravity functionals at ground level. The preprocessing of airborne gravity data consists of several independent steps such as low-pass filtering, a cross-over adjustment to minimize misfits at cross-overs of intersecting lines, and gridding. Each of these steps may introduce errors that accumulate in the course of processing, which can limit the accuracy and the resolution of the resulting gravity field.
For the inversion of the airborne gravity data at flight level into gravity functionals at the Earth's surface, several approaches can be used. Methods that have been successfully applied to airborne gravity data are integral methods and least-squares collocation, but both methods have some disadvantages. Integral methods require that the data are available in a much larger area than for which the gravity functionals are computed. A large cap size is required to reduce edge effects that result from missing data outside the target area. Least-squares collocation suffers much less from these errors and can yield accurate results, provided that the auto-covariance function gives a good representation of data in- and outside the area. However, the number of base functions equals the number of observations, which makes least-squares collocation numerically less efficient.
In this thesis a new methodology for processing airborne gravity data is proposed. It combines separate preprocessing steps with the estimation of gravity field parameters in one algorithm. Importantly, the concept of low-pass filtering is replaced by a frequency-dependent data weighting to handle the strong colored noise in the data. Frequencies at which the noise level is high get a lower weight than frequencies at which the noise level is low. Furthermore, bias parameters are estimated jointly with gravity field parameters instead of applying a cross-over adjustment. To parameterize the gravity potential a spectral representation is used, which means that the estimation results in a set of coefficients. These coefficients are used to compute gravity functional at any location on the Earth's surface within the survey area. The advantage of the developed approach is that it requires a minimum of preprocessing and that all data can be used as obtained at the locations where they are observed.
The performance of the developed methodology is tested using simulated data and data acquired in airborne gravimetry surveys. The goal of the simulations is to test the approach in a controlled environment and to make optimal choices for the processing of real data. For the numerical studies with simulated data, the new methodology outperforms the more traditional approaches for airborne gravity data processing. For the application of the developed methodology to real data, three data sets are used. The first data set comprises airborne gravity measurements over the Skagerrak area, obtained as part of a joint project between several European institutions in 1996. This survey provided accurate airborne gravity data, and because good surface gravity data are available within the area, the data set is very useful to test the performance of the approach. The second data set was obtained by the GeoForschungsZentrum Potsdam during a survey off the coast of Chile in 2002. This data set, which has a lower accuracy than the first data set, is used to investigate the estimation of non-gravitational parameters such as biases and scaling factors. The final data set that is used consists of airborne gravity data acquired by Sander Geophysics Limited in 2003. The survey area is located near Timmins, Ontario and is much smaller than the area of the other data sets. The small size of the area and the high accuracy of the data make it a challenging data set for regional gravity modeling.
The computational experiments with real data show that the performance of the developed methodology is at the same level as traditional methods in terms of gravity field errors. However, it provides a more flexible and powerful approach to airborne gravity data processing. It requires a minimum of preprocessing and all observations are used in the determination of a regional gravity field. The frequency-dependent data weighting is successfully applied to each data set. The approach provides a statistically optimal solution and is a formalized way to handle colored noise. A noise model can be estimated from a posteriori least-squares residuals in an iterative way. The procedure is purely data-driven and, unlike low-pass filtering, does not depend on previous experience of the user. The developed methodology allows for the simultaneous estimation of non-gravitational parameters with the gravity field parameters. A testing procedure should be applied, however, to avoid insignificant estimations and high correlations. For the Chile data set a significant improvement of the estimated gravity field is obtained when bias and scale factors are estimated from the observations. The results of the computations with the real data sets show the high potential of using airborne gravimetry to obtain accurate gravity for geodetic and geophysical applications.Note de contenu : 1 Introduction
1.1 Background
1.2 Objectives
1.3 Outline
2 Airborne gravimetry
2.1 Historical overview
2.2 The principle of airborne gravimetry
2.3 Mathematical models
2.4 Applications and opportunities
3 Processing of airborne gravity data
3.1 Pre-processing
3.2 Inversion of airborne gravity data
3.3 Discussion
4 Combined data processing and inversion
4.1 Gravity field representation
4.2 Inversion methodology
4.3 Regularization and parameter choice rule
4.4 Frequency-dependent data weighting
4.5 Estimation of non-gravitational parameters
4.6 Edge effect reduction
4.7 Combination with prior information
5 Application to simulated data
5.1 Description of the data
5.2 Computations with noise-free data
5.3 Computations with data corrupted by white noise
5.4 Computations with data corrupted by colored noise
5.5 Bias and drift handling
5.6 Summary of the optimal solution strategy
6 Application to airborne gravimetric survey data
6.1 Skagerrak data set
6.2 Chile data set
6.3 Timmins, Ontario data set
6.4 Summary and discussion
7 Conclusions and recommendations
7.1 Conclusions .
7.2 Recommendations.
A Pre-processing of airborne gravity data
A.1 GPS processing
A..2 Gravity processing
B Coordinate transformation
C Least-squares collocation and Hilbert spaces
C.1 Definition of a Hilbert space and some properties
C.2 Reproducing kernel Hilbert spaces
C.3 Least-squares collocation
D Derivation of the ZOT regularization matrix
E Modification of the base functionsNuméro de notice : 15494 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : sans En ligne : https://www.ncgeo.nl/downloads/70Alberts.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62736 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 15494-01 30.42 Livre Centre de documentation Géodésie Disponible PermalinkA study reference frame consistency in recent Earth gravitational models / Christopher Kotsakis in Journal of geodesy, vol 83 n° 1 (January 2009)
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