Descripteur
|
Termes IGN > sciences naturelles > sciences de la Terre et de l'univers > géosciences > géophysique interne > géodésie > géodésie physique > gravimétrie > gravimétrie en mer
gravimétrie en mer |
Documents disponibles dans cette catégorie (17)
Ajouter le résultat dans votre panier Affiner la recherche Interroger des sources externesEtendre la recherche sur niveau(x) vers le bas
Comparison and evaluation of high-resolution marine gravity recovery via sea surface heights or sea surface slopes / Shengjun Zhang in Journal of geodesy, vol 95 n° 6 (June 2021)
Titre : Comparison and evaluation of high-resolution marine gravity recovery via sea surface heights or sea surface slopes Type de document : Article/Communication Auteurs : Shengjun Zhang, Auteur ; Adili Abulaitijiang, Auteur ; Ole Baltazar Andersen, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 66 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] données altimétriques
[Termes IGN] données Jason
[Termes IGN] géodésie marine
[Termes IGN] gravimétrie en mer
[Termes IGN] hauteurs de mer
[Termes IGN] image Cryosat
[Termes IGN] relief sous-marin
[Termes IGN] SARAL
[Termes IGN] série temporelle
[Termes IGN] surface de la merRésumé : (auteur) There are two dominating approaches of modeling the marine gravity field based on satellite altimetry observations. In this study, the marine gravity field is determined in four selected areas (Northwestern Atlantic, Hawaii ocean area, Mariana Trench area, and Aegean Sea) by using exact same input datasets but different methods which are based on sea surface height (SSH) and sea surface slope (SSS), respectively. The impact of the methodology is evaluated by conducting validations with shipborne gravity observation. The CryoSat-2, Jason-1/2, and SARAL/Altika geodetic mission data (similarly 3-year-long time series) are firstly retracked by the two-pass retracker. After that, the obtained SSHs are used for the derivation of geoid undulations and vertical deflections, and then for the resulting marine gravity field separately. The validation results indicate that the SSH-based method has advantages in robustly estimating marine gravity anomalies near the coastal zone. The SSS-based method has advantages over regions with intermedium ocean depths (2000–4000 m) where seamounts and ridges are found, but obvious disadvantages when the ocean currents flow along the north–south direction (e.g., western boundary currents) or the topography features north–south directional trenches. In the deep ocean where the seafloor topography is plain and smooth, the two methods have similar accuracy. Numéro de notice : A2021-433 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01506-8 Date de publication en ligne : 27/05/2021 En ligne : https://doi.org/10.1007/s00190-021-01506-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97799
in Journal of geodesy > vol 95 n° 6 (June 2021) . - n° 66[article]Développement d’une méthode innovante pour l’ajustement des paramètres internes du système de gravimétrie sous-marine GraviMob / Ossama Kharbou (2021)
Titre : Développement d’une méthode innovante pour l’ajustement des paramètres internes du système de gravimétrie sous-marine GraviMob Type de document : Mémoire Auteurs : Ossama Kharbou, Auteur Editeur : Le Mans : Ecole Supérieure des Géomètres et Topographes ESGT Année de publication : 2021 Importance : 76 p. Format : 21 x 30 cm Note générale : bibliographie
Mémoire présenté en vue d'obtenir le diplôme d'ingénieur ESGT, spécialité Géomètre et TopographeLangues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] ajustement de paramètres
[Termes IGN] analyse de données
[Termes IGN] gravimétrie en mer
[Termes IGN] gravimétrie mobile
[Termes IGN] instrument de géodésie
[Termes IGN] modèle mathématique
[Termes IGN] régression linéaireIndex. décimale : ESGT Mémoires d'ingénieurs de l'ESGT Résumé : (auteur) Le système de gravimétrie mobile GraviMob, est un système simple et innovant qui permet de mesurer les 3 composantes de l’accélération de la pesanteur, en fond de mer, en utilisant six accéléromètres capacitifs divisés en deux triades. Le traitement des mesures nécessite une connaissance de onze paramètres internes dont la détermination est essentielle pour estimer les trois composantes ou la norme de g. Les valeurs de ces paramètres varient en fonction de la température. L’ajustement de ces paramètres internes dans une enceinte climatique, a permis de tracer leur évolution, et ainsi proposer, et valider statistiquement, des modèles polynomiaux de degré 4, permettant de déterminer la valeur de chaque paramètre en fonction de la température sur une étendue de mesure de 4°C à 18°C. Note de contenu : Introduction
1- Instrumentation
2- Traitement
ConclusionNuméro de notice : 15286 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire ingénieur ESGT Organisme de stage : Laboratoire Géomatique et Foncier En ligne : https://dumas.ccsd.cnrs.fr/MEMOIRES-CNAM/dumas-03563094 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101470
Titre : Applying iterative method to solving high-order terms of seafloor topography Type de document : Article/Communication Auteurs : Diao Fan, Auteur ; Shanshan Li, Auteur ; Shuyu Meng, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : pp 63 - 85 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie
[Termes IGN] Chine, mer de
[Termes IGN] fond marin
[Termes IGN] force de gravitation
[Termes IGN] gravimétrie en mer
[Termes IGN] inversion
[Termes IGN] itération
[Termes IGN] relief sous-marinRésumé : (auteur) We introduce an iterative inversion method to address the problems in high-order seafloor topography inversion using gravity data (gravity anomaly and vertical gravity gradient anomaly), such as the difficulty in computing the equation and the uniqueness of the calculation results. A part of the South China Sea is selected as the experimental area. Considering the coherence and admittance function of gravity topography and vertical gravity gradient topography, the inversion band of the gravity anomaly and vertical gravity gradient anomaly in the study area is 30 km–120 km. Seafloor topography models of different orders are constructed using an iterative method, and the performance of each seafloor topography model is analyzed against ETOPO1 and other seafloor topography models. The experimental results show that as the inversion order increases, the clarity and richness of seafloor topographic expression continuously improve. However, the accuracy of seafloor topography inversion does not improve significantly when the inversion order exceeds a certain value, which is related to the contribution of high-order seafloor topography to gravity information. The results show that the accuracy of BGT4 (inversion model constructed by the gravity anomaly) is slightly poorer than that of BVGGT4 (inversion model constructed by the vertical gravity gradient anomaly) in areas with complex topography, such as multi-seamounts and trenches, and the results are generally better in areas with flat seafloor topography. Numéro de notice : A2020-463 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2019.1670298 Date de publication en ligne : 08/10/2019 En ligne : https://doi.org/10.1080/01490419.2019.1670298 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95125
in Marine geodesy > Vol 43 n° 1 (January 2020) . - pp 63 - 85[article]
Titre : Amundsen Sea bathymetry: the benefits of using gravity data for bathymetric prediction Type de document : Article/Communication Auteurs : M. Mcmillan, Auteur ; A. Sheperd, Auteur ; D. Vaughan, Auteur ; et al., Auteur Année de publication : 2009 Article en page(s) : pp 4223 - 4228 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bathymétrie
[Termes IGN] Amundsen, mer d'
[Termes IGN] Arctique, océan
[Termes IGN] données altimétriques
[Termes IGN] fond marin
[Termes IGN] gravimétrie en mer
[Termes IGN] image ERS
[Termes IGN] levé gravimétrique
[Termes IGN] méthode de Monte-Carlo
[Termes IGN] plateau continental
[Termes IGN] prédiction
[Termes IGN] profondeurRésumé : (Auteur) Bathymetric charts are essential for modeling oceanic processes, yet, in remote areas, direct measurements of seafloor depth are often scarce. It is possible to augment sparse depth soundings with dense satellite-derived gravity data to provide additional bathymetric detail in regions devoid of sounding data. We demonstrate this method by using marine gravity derived from the European Remote Sensing (ERS-1) satellite altimeter, combined with depth soundings, to form a bathymetric prediction of the Amundsen Sea, West Antarctica. We estimate the root mean square error of depth estimates at unsurveyed locations in our solution to be ~120 m. We use a Monte Carlo method to assess the value of gravity as a bathymetric predictor in sparsely surveyed regions by comparing our solution to predictions formed from depth soundings alone. When less than ~11% of 10-km grid cells contain depth soundings, inclusion of gravity data improves the depth accuracy of the solution by up to 17%, as compared to a minimum curvature surface interpolation of the depth soundings alone. When depth data are sparse, our gravity-derived prediction reveals additional short-wavelength bathymetric features, such as troughs on the continental shelf, which are not resolved by interpolations of the depth soundings alone. Copyright IEEE Numéro de notice : A2009-493 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2009.2023665 En ligne : https://doi.org/10.1109/TGRS.2009.2023665 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30122
in IEEE Transactions on geoscience and remote sensing > vol 47 n° 12 Tome 2 (December 2009) . - pp 4223 - 4228[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 065-09121B RAB Revue Centre de documentation En réserve L003 Disponible
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)
Code-barres Cote Support Localisation Section Disponibilité 15494-01 30.42 Livre Centre de documentation Géodésie Disponible PermalinkPermalinkNational report to the general assembly, Saporo, Japan, June 30 - July 11, 2003 (Bulletin de Journal of the geodetic society of Japan) / National committee for geodesy in Japan
PermalinkMare nostrum, Geomed report - 4 [Selected papers from fourth working meeting, Thessaloniki, March 21 - 22, 1994] / D. Arabelos (1994)
PermalinkPermalinkPermalinkPermalinkGravity expeditions 1948-1958. Volume 5 Complete results with isostatics reduction / G.J. Bruins (1960)
PermalinkPermalinkPermalink
