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Titre : e 2 .Motion Earth System Mass Transport Mission (Square) : Concept for a Next Generation Gravity Field Mission, Final Report of Project “Satellite Gravimetry of the Next Generation (NGGM-D)" Type de document : Rapport Auteurs : NGGM-D Team, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2014 Collection : DGK - B, ISSN 0065-5317 Importance : 200 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8597-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données GRACE
[Termes IGN] masse de la TerreIndex. décimale : 30.42 Gravimétrie Résumé : (Auteur) The main goal of this study was the development of a mission concept for the long term high precision and homogeneous determination of the time variable gravity field with significant improved sensitivity and spatial resolution as compared to nowadays techniques, which are used on GRACE and GRACE-FO. This goal is supported by the international science community and is content of resolutions issued by several institutions and science communities like for example resolution No. 2 of the International Union of Geodesy and Geophysics (IUGG; Melbourne, 2011, refer to: http://iugg.org/resolutions). Long duration, higher sensitivity and improved spatial/temporal resolution of mass ariation observations are required by more or less all geoscience disciplines in order to make their models more realistic and in order to assimilate them into these models. Long term analyses and calibration of geophysical models contribute to a better understanding of the coupling of the different phenomena and consequently improve models and provide more realistic prediction capabilities. For this reason, in future a continuous monitoring of mass distribution in the Earth system is required.[...] Note de contenu : 1 NGGM - D Study Approach
2 Sciences and Mission Requirements
3 Orbit Configuration
4 Attitude Determination and Control
5 Instrument Concept
6 Generation of Simulated Observations
7 Numerical Simulations
8 e2 .motion Mission Concept
9 References
AnnexesNuméro de notice : 15824 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport d'étude technique En ligne : http://dgk.badw.de/fileadmin/docs/b-318.pdf Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74911 Exemplaires(1)
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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 Exemplaires(1)
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Titre : Regional gravity field modelling with radial basis functions Type de document : Thèse/HDR Auteurs : Tobias Wittwer, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2009 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 72 Importance : 190 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-315-0 Note générale : Bibliographie
Document téléchargeable sur le site de NCG : voir lien dans la noticeLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Antarctique
[Termes IGN] Canada
[Termes IGN] champ de pesanteur local
[Termes IGN] données GOCE
[Termes IGN] données GRACE
[Termes IGN] factorisation de Cholesky
[Termes IGN] filtre de Wiener
[Termes IGN] fonction de base radiale
[Termes IGN] Groenland
[Termes IGN] harmonique sphérique
[Termes IGN] levé gravimétrique
[Termes IGN] modèle de géopotentiel
[Termes IGN] modèle mathématiqueIndex. décimale : 30.42 Gravimétrie Résumé : (Auteur) Terrestrial gravimetry, airborne gravimetry, and the recent dedicated satellite gravity missions Challenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity and Ocean Circulation Explorer (GOCE) provide us with high-quality, high-resolution gravity data, which are used in many application areas such as
1. the computation of global static gravity fields, in support of precise orbit determination of many Earth observation satellites;
2. the quantification and interpretation of mass transport in the Earth system such as the shrinking of ice sheets, the shifting of ocean currents, and water storage variations;
3. the computation of high resolution regional and local gravity fields in support of height system realisation and the modelling of reservoirs and geophysical features.
Traditionally, for each data set (satellite, airborne, terrestrial) dedicated data processing schemes have been developed using different estimation principles, parametrisations, etc. The optimal combination of different data sets would benefit of a methodology that can be used for any type of data. Elements of this methodology comprise a uniform parametrisation, estimation principle, data weighting scheme, regularisation, and error propagation.
In the framework of this thesis, such a methodology is developed. It uses radial basis functions (RBFs) as parametrisation. They have parameters that allow us to tune their approximation properties as function of the data coverage and distribution and the signal variations. This makes them equally well suited for global and local parametrisation. Moreover, there exists an analytical relationship between a spherical harmonic representation and a radial basis function representation, which allows the latter to be transformed into the former, without any approximation error. Among others, this has the advantage that one can make use of existing processing tools, such as spectral analysis.
Although radial basis functions are not new in gravity field modelling, there are many important issues which have not yet been addressed or require further research. The main research question underlying this thesis is: "Are radial basis functions a suitable parametrisation for global and regional models of the mean and time-variable gravity field, and if so, how do they perform compared with spherical harmonic solutions?" Directly related to this is the question: "Are there situations where radial basis functions models outperform spherical harmonic solutions?" The answer to both questions is positive as will be shown in this thesis.
There are two important aspects that determine the quality of a gravity field model based on radial basis functions: 1) the spatial distribution of the radial basis functions, i.e. the basis function network design, and 2) the choice of the bandwidths of the radial basis functions. For both problems, semi-automatic algorithms have been developed. Data-adaptive network design and local refinement avoid respectively over- and under-parametrisation by fine-tuning the basis function network based on the data. The basis function bandwidth is determined by optimising the fit to the data including control data.
The computation of regional gravity fields constitutes a considerable numerical workload, especially since the methodology presented here does not use an iterative normal equation solver (e.g., the preconditioned conjugate gradient method). Instead, a Cholesky solver is used, which requires the assembly of the complete normal equation system. For this purpose the program is numerically optimised and fully parallelised for hybrid high performance computer architectures. This guarantees optimal performance on all types of parallel computers and handles the memory requirements.
The modelling of satellite data with radial basis functions is investigated using real data of the GRACE satellites collected over the period 2003-2006. An optimal Wiener filter has been developed for radial basis functions in line with the optimal Wiener filter approach previously developed at DEOS for spherical harmonic representations. Monthly GRACE gravity models computed using radial basis function are compared to spherical harmonic models, and validated using independent data provided by the Ice Cloud and Land Elevation Satellite (ICESat), radar altimetry satellites, and the global hydrological model PCR-GLOBWB. Two applications were considered: 1) mass variations over Greenland and Antarctica and 2) water storage variations in river basins. The results show that the radial basis function approach yields solutions that are of at least the same quality as global models using spherical harmonics. There is evidence that radial basis functions may provide better spatial resolution and more realistic amplitudes in particular in high-latitude areas. For instance, it will be shown that radial basis function solutions detected signal that could not be seen in spherical harmonic solutions.
Two test areas are used for regional gravity field modelling using real terrestrial data: An area in the northeastern USA and a larger area in eastern Canada. The results show that the data-adaptivity and local refinement algorithms developed in the framework of this thesis provide good solutions of constant quality regardless of the initially chosen grid spacing. The models are compared to the official regional geoid models GEOID03 and CGG05, respectively. In both cases, rms errors of several centimetres remain, which are attributed to different input data and processing strategies.
The combination of satellite and terrestrial data is tested using simulated global and regional data sets. It is shown that a joint inversion of the two data sets yields combined solutions which are significantly better than a solution using the traditional remove-restore approach. The addition of satellite data with the corresponding stochastic model compensates the reduced quality of the terrestrial data at long wavelengths.
The examples show that the regional modelling methodology presented here is a very flexible approach that can be applied to all types of gravity data and data distributions, regardless of application, data source, and area size. The quality of the solutions is at least equal to the solutions developed for the stand-alone inversion of individual data sets, while radial basis functions offer numerical benefits. As a result, this approach is already used for marine geoid modelling, and recommended for the modelling of airborne gravity data and data of the GOCE satellite, and for the joint inversion of satellite, airborne and ground-based gravity data.Note de contenu : Nomenclature
1 Introduction
1.1 Background
1.2 Motivation
1.2.1 Regional modelling from satellite data
1.2.2 Regional modelling from terrestrial data
1.2.3 Combined modelling of satellite and terrestrial data
1.2.4 Radial basis functions
1.3 Prior research on radial basis functions
1.4 Research objectives
1.5 Outline of thesis
2 Radial basis functions
2.1 Gravity field representations
2.1.1 Spherical harmonics
2.1.2 Radial basis functions
2.2 RBF types and behaviour in the spectral domain
2.3 Behaviour in the spatial domain
2.4 Relation of RBFs to a spherical harmonic representation
2.5 Choice of RBF characteristics
2.5.1 Choice of the kernel
2.5.2 Bandwidth selection
2.6 RBF network design
2.6.1 Grids
2.6.2 Adaptation to data
2.6.3 Local refinement
2.7 Multi-scale modelling
2.7.1 Introduction
2.7.2 Methodology
2.7.3 Filtering
3 Mathematical model and estimation principle
3.1 Functional model
3.2 Stochastic model
3.3 Least-squares estimation and regularisation
3.4 Solution strategies
3.4.1 Cholesky factorisation
3.4.2 Conjugate gradients
3.5 Variance component estimation .
3.5.1 Normal equations
3.5.2 Variance component estimation
3.5.3 Stochastic trace estimation
4 Numerical aspects
4.1 Numerical optimisation
4.1.1 Constant expressions in "do"-loops
4.1.2 Computation of the design matrix
4.1.3 Normalisation of coordinates
4.1.4 Normalisation of basis functions
4.2 Fast synthesis
4.3 Parallelisation
4.3.1 Problem description
4.3.2 Parallel computer architectures .
4.3.3 Parallelisation for shared memory computers
4.3.4 Parallelisation for distributed memory computers
4.3.5 Hybrid parallelisation
4.3.6 Results of parallelisation
4.4 Summary and conclusions
5 Gravity field modelling from satellite data
5.1 Functional model
5.1.1 Three-point range combination approach
5.1.2 Residual accelerations
5.1.3 Equivalent water heights
5.1.4 Trend and signal amplitude estimation
5.2 Stochastic model
5.3 Optimal filtering
5.3.1 Introduction
5.3.2 Signal covariance matrix computation
5.3.3 Noise level estimation
5.4 RBF network design
5.4.1 Grid choice
5.4.2 Data-adaptivity and local refinement
5.4.3 Parametrised area
5.5 Bandwidth selection
5.6 Results.
5.6.1 Comparison of unfiltered RBF and spherical harmonic solution
5.6.2 Models used for comparison
5.6.3 Recovery of ice mass loss in Greenland and Antarctica
5.6.4 Recovery of terrestrial water storage variations
5.7 Summary and conclusions
6 Local gravity field modelling from terrestrial data
6.1 Functional model
6.1.1 Functional model for gravity disturbances
6.1.2 Functional model for gravity anomalies
6.1.3 Functional model for height anomalies
6.2 RBF network design
6.2.1 Grid choice
6.2.2 Data-adaptivity and local refinement
6.2.3 Parametrised area
6.3 Bandwidth selection
6.4 Results
6.4.1 Northeastern USA
6.4.2 Canada
6.5 Summary and conclusions
7 Combined modelling of satellite and terrestrial data
7.1 Combination strategies
7.1.1 Remove-restore approach
7.1.2 High-pass filtering
7.1.3 Direct combination
7.1.4 Combination with satellite-only solution
7.2 RBF network design and bandwidth selection
7.3 Results
7.3.1 Global test
7.3.2 Regional test
7.4 Summary and conclusions
8 Summary, conclusions and recommendations
8.1 Summary and conclusions
8.2 Recommendations for further researchNuméro de notice : 15511 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD thesis En ligne : https://www.ncgeo.nl/index.php/en/publicatiesgb/publications-on-geodesy/item/258 [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62744 Exemplaires(1)
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Titre : Absolute airborne gravimetry Type de document : Thèse/HDR Auteurs : Henri Baumann, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2005 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 69 Importance : 142 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-12-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] accélération
[Termes IGN] étude de faisabilité
[Termes IGN] GPS-INS
[Termes IGN] gravimètre absolu
[Termes IGN] gravimétrie aérienne
[Termes IGN] traitement de donnéesIndex. décimale : 30.42 Gravimétrie Résumé : (Auteur) This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation.
The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber.
The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data.
In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airbome absolute gravimetry is feasible and has a spatial resolution comparable to the one of the relative airborne gravimetry. For a wavelength on the order of 11 km the mean value of the resolution of the estimated gravity is 9.7 mGal.
Finally some suggestions are formulated for the improvement of the system which should simplify its use, increase the accuracy and reduce its price.Numéro de notice : 13266 Affiliation des auteurs : non IGN Autre URL associée : http://dx.doi.org/10.3929/ethz-a-004701048 Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD thesis : Géodésie et photogrammétrie : ETH Zurich : 2005 DOI : 10.3929/ethz-a-004701048 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-69.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54947 Exemplaires(2)
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Titre : Modelling of the gravimetric effects induced by vertical air mass shifts Type de document : Monographie Auteurs : D. Simon, Auteur Editeur : Francfort sur le Main : Bundesamt für Kartographie und Geodäsie Année de publication : 2003 Collection : Mitteilungen des Bundesamtes für Kartographie und Geodäsie, ISSN 1436-3445 num. 21 Importance : 100 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-89888-001-5 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] anomalie de pesanteur
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] masse d'air
[Termes IGN] modèle atmosphériqueIndex. décimale : 30.42 Gravimétrie Résumé : (Auteur) The superconducting gravimeters used within the framework of the Global Geodynamic Project (GGP) performed for the determination of the temporal variations of the gravity field nowadays have a resolution in the NanoGal range and drift rates of only a few µgal/year. This has led to an improvement of the chances to achieve a more precise model-related acquisition of the global gravity field, allowing also gravity field components with lower amplitudes having hitherto remained unconsidered to be modelled and identified by means of the relevant measuring series. These components comprise also the effects of vertical air mass displacements computed on the basis of radiosonde data, which are dealt with in the present contribution. In section 2 first the two models used for demonstrating this effect are described including the geophysical and meteorological fundamentals of modelling. Subsequently, the procram system AMACON developed for this purpose and the single computational steps are explained by test examples (section 3). Following this method, in section 4 the gravity variations caused by vertical air mass displacements in Europe and at the North American East coast for the observation period 1998-2000 are modelled with a sampling rate of 24 hours, for which purpose the measuring data sets of 16 European and 12 American radiosonde stations were used. These data are supplemented by the model curve of a radiosonde station (Neumayer Station, Antarctica) situated on the southern hemisphere, whose seasonal component is deferred, as expected, by 6 months. The data obtained on the order of magnitude of this effect constitute the most important outcome of this modelling project performed on a large regional level. It becomes evident that this gravity component cannot be neglected on any European or North American gravimeter station, given that both its short-period components (period range: 3-50 days) and its seasonal components reach in those areas double amplitudes of 1,5-2,0µgGal. In section 5 the evidence of the modelled gravity effect in gravimetric measuring series is discussed. For this purpose, the data series of the two BKG stations Bad Homburg and Medicina were made use of, which had been subjected to a closer analysis beforehand. It proves that the chances of identifying and eliminating the gravity variations caused by vertical air mass displacements are not so small at all. However, in order to be successful in pursuing this objective the components of the local, regional, and global gravity components as a result of horizontal air mass displacements must be removed more accurately from the measuring series than hitherto, which will now be facilitated when using as basis the current prediction models LM (Local Model) and GME (Global Model) provided by the German Meteorological Service (GMS). Numéro de notice : 13153 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54896 Exemplaires(2)
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