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The impact of the dynamic sea surface topography on the quasi-geoid in shallow coastal waters / D.C. Slobbe in Journal of geodesy, vol 88 n° 3 (March 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 3 (March 2014) . - pp 241 - 261 Titre : The impact of the dynamic sea surface topography on the quasi-geoid in shallow coastal waters Type de document : Article/Communication Auteurs : D.C. Slobbe, Auteur ; R. Klees, Auteur Année de publication : 2014 Article en page(s) : pp 241 - 261 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] levé gravimétrique [Termes IGN] marée océanique [Termes IGN] Nord, mer du [Termes IGN] quasi-géoïde [Termes IGN] surface de la mer [Termes IGN] topographie Résumé : (Auteur) In this study, we examine the impact of instantaneous dynamic sea surface topography (DT) corrections to be applied to altimeter-derived sea surface slopes on the quasi-geoid in the shallow and coastal waters of the North Sea. In particular, we investigate the added value of DT corrections obtained from a shallow-water hydrodynamic model. These corrections comprise the contributions of ocean tides, wind- and pressure-driven (surge), and density-driven (baroclinic) water-level variations including the interactions between them. As a reference, we used tidal corrections derived from the global ocean tide model GOT4.7, surge corrections derived from the MOG2D model, and corrections for the time-averaged baroclinic contribution computed as differences between the DTU10 mean sea surface model and the EGG08 quasi-geoid. From a spectral analysis, we found that the baroclinic and surge parts of the DT mainly contribute to improvements in the signal-to-noise ratio (SNR) at longer wavelengths down to 100200 km and that the improvements increase towards the southern North Sea. We also found that the shallow-water hydrodynamic model provides better tidal corrections compared to the GOT4.7 global ocean tide model, which are most pronounced in the southern North Sea and affect almost the entire spectrum. Very small differences (mostly below +2 cm ) are observed between the quasi-geoid solutions obtained using the different sets of DT corrections. We showed that the variance component estimation provides too optimistic variance factors for the shipboard data set relative to the altimeter-derived quasi-geoid slopes. Hence, the limited impact of DT corrections is due to the fact that altimeter-derived quasi-geoid slopes hardly contribute to the estimated quasi-geoid if shipboard gravity data are included. When computing quasi-geoid solutions without shipboard gravity data, we found that less accurate or incomplete DT corrections may cause errors in the quasi-geoid with systematic spatial patterns. These systematic patterns disappear or are reduced significantly when using the DT corrections provided by the shallow-water hydrodynamic model. The main contributor to this improvement is the better tidal correction provided by the shallow-water hydrodynamic model compared to the GOT4.7 global ocean tide model. Seen the improvements of the global ocean tide models over the last two decades, we expect that in the near future global ocean tide models perform as well as dedicated regional models such as DCSM. Critical issue is, however, access to high-quality local bathymetric data. Numéro de notice : A2014-134 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0679-3 Date de publication en ligne : 18/12/2013 En ligne : https://doi.org/10.1007/s00190-013-0679-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33039 [article]

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Lowest astronomical tide in the North Sea derived from a vertically referenced shallow water model, and an assessment of its suggested sense of safety / D. Slobbe in Marine geodesy, vol 36 n° 1 (January - March 2013)  

Public [article]  inMarine geodesy > vol 36 n° 1 (January - March 2013) . - pp 31 - 71 Titre : Lowest astronomical tide in the North Sea derived from a vertically referenced shallow water model, and an assessment of its suggested sense of safety Type de document : Article/Communication Auteurs : D. Slobbe, Auteur ; R. Klees, Auteur ; M. Verlaan, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 31 - 71 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Océanographie [Termes IGN] géoïde local [Termes IGN] geoïde marin [Termes IGN] marée océanique [Termes IGN] niveau de la mer [Termes IGN] niveau moyen des mers [Termes IGN] Nord, mer du [Termes IGN] réduction Résumé : (Auteur) Water level reduction with global navigation satellite systems in bathymetric surveying requires knowledge of the ellipsoidal heights of lowest astronomical tide (LAT). The traditional approach uses tidal water levels of an ocean tide model, which are subtracted from mean sea level (MSL). This approach has two major drawbacks: the modeled water levels refer to an equipotential surface, which differs from MSL, and MSL may not be known close to the coast. Here, we propose to model LAT directly relative to an equipotential surface (geoid). This is conceptually consistent with the flow equations and allows the inclusion of temporal MSL variations into the LAT definition. Numerical experiments for the North Sea show that significant differences between the traditional and the pursued approach exist if average monthly variations in MSL are included. A validation of the modeled LAT using tide gauge records reveals systematic errors, which we attribute to both the model and the tidal analysis procedure. We also show that the probability that water levels drop below LAT is high, with maximum frequency of once per week in the eastern North Sea. Therefore, we propose to reconsider the deterministic concept of LAT by a probabilistic chart datum concept, and we quantified the differences between them. Numéro de notice : A2013-245 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2012.743493 Date de publication en ligne : 13/03/2013 En ligne : https://doi.org/10.1080/01490419.2012.743493 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32383 [article]

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Reconstruction des séries marégraphiques de la mer du Nord et de Norvège / Raphaël Baucry (2012) 

Public Titre : Reconstruction des séries marégraphiques de la mer du Nord et de Norvège Type de document : Mémoire Auteurs : Raphaël Baucry, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2012 Importance : 57 p. Format : 21 x 30 cm Note générale : Bibliographie Rapport de stage de travaux de fin d'études, cycle des ingénieurs diplômés de l'ENSG, Mastère PPMD Langues : Français (fre) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] changement climatique [Termes IGN] décomposition en fonctions orthogonales empiriques [Termes IGN] données marégraphiques [Termes IGN] fonction orthogonale [Termes IGN] niveau de la mer [Termes IGN] Nord, mer du [Termes IGN] Norvège [Termes IGN] série temporelle Index. décimale : MPPMD Mémoires du mastère spécialisé Photogrammétrie, Positionnement et Mesures de Déformation Résumé : (Auteur) Dans le contexte actuel du réchauffement climatique, l'une des plus importantes conséquences, l'élévation du niveau marin devient depuis plusieurs décennies un enjeu primordial. Les observations du niveau de la mer constituent donc une base de données indispensable pour comprendre et décrire ses variations. La marégraphie est l'une des sources d'enregistrement les plus longues actuellement disponible (parfois depuis 300 ans) mais présente aussi certaines lacunes sur les séries observées. L'objectif de cette étude est donc de remédier à ces lacunes en proposant de reconstruire les séries du niveau marin. Ce Travail de Fin d'Études présente donc un exemple d'application de reconstruction du niveau de la mer dans la mer du Nord et la mer de Norvège sur 38 marégraphes sélectionnés. Cette méthode de reconstruction sur les valeurs manquantes est réalisée via la technique de décomposition de matrice en EOFs à partir de l'algorithme de Beckers & Rixen (2003). Une série de tests a été réalisée afin de tester la robustesse et l'optimisation de la méthode. Note de contenu : Introduction 1. Problématique de la montée du niveau de la mer. 1.1 Impacts et causes de cette hausse du niveau marin 1.2 Inhomogénéités spatiales et temporelles de ces variations 2. Données : description et choix des différentes données 2.1 Description des méthodes d'études de la hausse des mers 2.2 Description des données retenues 3. Zone d'étude : critères de choix des marégraphes 3.1 Choix du bassin océanique 3.2 Choix des stations 4. Méthodes de reconstructions des séries, comparaisons des fonctions temporelles et spatiales 4.1 La technique de reconstruction par les EOFs 4.2 Les différentes séries et leurs reconstructions 4.3 Vérification de la stabilité temporelle des EOFs spatiaux 5. Résultats des tests de validation des reconstructions 5.1 Méthode et marégraphes utilisés pour les tests de reconstructions 5.2 Tests de reconstructions 6. Discussion des résultats 6.1 Comparaison des reconstructions partielle et totale 6.2 Les tests de reconstruction Conclusion Numéro de notice : 20738 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire masters divers Organisme de stage : Laboratoire LIttoral ENvironnement et Sociétés LIENSs Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=51145

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Estimating sea floor dynamics in the southern North Sea to improve bathymetric survey planning / L. Dorst (2009)  

Public Titre : Estimating sea floor dynamics in the southern North Sea to improve bathymetric survey planning Type de document : Thèse/HDR Auteurs : L. Dorst, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2009 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 69 Importance : 220 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-311-2 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bathymétrie [Termes IGN] bathymétrie [Termes IGN] covariance [Termes IGN] déformation de la croute terrestre [Termes IGN] fond marin [Termes IGN] géodynamique [Termes IGN] géostatistique [Termes IGN] interpolation [Termes IGN] krigeage [Termes IGN] marée océanique [Termes IGN] morphogenèse [Termes IGN] nivellement indirect [Termes IGN] Nord, mer du [Termes IGN] océanographie dynamique [Termes IGN] port [Termes IGN] relèvement [Termes IGN] Rotterdam (Pays-Bas) [Termes IGN] sable [Termes IGN] vague Index. décimale : 32.10 Bathymétrie Résumé : (Auteur) Safe nautical charts require a carefully designed bathymetric survey policy, especially in shallow sandy seas that potentially have dynamic sea floor patterns. Bathymetric resurveying at sea is a costly process with limited resources, though. A pattern on the sea floor known as tidal sand waves is clearly present in bathymetric surveys, endangering navigation in the Southern North Sea because of the potential dynamics of this pattern. An important factor in an efficient resurvey policy is the type and size of sea floor dynamics. The uncertainties of measurement and interpolation associated with the depth values enable the statistical processing of a time series of surveys, using deformation analysis. Currently, there is no procedure available that satisfies the Royal Netherlands Navy requirements. Therefore, a deformation analysis procedure is designed, implemented and tested in such a way that the procedure works on bathymetric data and satisfies the Royal Netherlands Navy requirements. Also, it is necessary to develop a procedure that translates the results into changes of the resurvey policy, taking into account their confidence intervals. To describe the sea floor statistically, we assume the sea floor to consist of a spatial trend function (or characterization) and a residual function (or dispersion). Such a description is called a representation. The covariances between positions are expressed in a covariance function, based on the residual function. The covariance function is used by Kriging, an interpolation procedure that propagates the variances and covariances of the data points to variances of the interpolated values. This approach is used widely for spatial analyses, like the interpolation of a bathymetric data set. The method that we propose uses Kriging to produce a time series of grids of depth values and their variances. Subsequently, it uses deformation analysis, a statistical procedure based on testing theory. Our application of deformation analysis is particularly aimed at the detection of dynamics in areas with tidal sand waves, resulting in parameter estimates for the sea floor dynamics, and their uncertainty. We apply the method to sea floor representations both with and without a sand wave pattern. A test scenario is set up, consisting of a survey of an existing area in the Southern North Sea, for which dynamics are simulated. The results show that the proposed method detects different types of sea floor dynamics well, leading to satisfactory estimates of the corresponding parameters. We show results for the anchorage area Maas West near the Port of Rotterdam, the Netherlands first. The area is divided into 18 sub-areas. The results show that a sand wave pattern is detected for most of the sub-areas, and a shore-ward migration is detected for a majority of them. The estimated migration rates of the sand waves are up to 7.5 m/yr, with a 95% confidence interval that depends on the regularity of the pattern. The results are in confirmation with previously observed migration rates for the Southern North Sea, and with an idealized process-based model. Thereafter, we analyze several other areas for which a time series of surveys is available in the bathymetric, archives of the Netherlands Hydrographic Service, to study the spatial variations in sea floor dynamics. We present results for several sand wave areas and a single flat area. In some of those areas, dredging takes place, to guarantee minimum depths. The results indicate sand wave migration in areas close to the coast, and bed level changes of the order of decimeters. The dominant wavelength of the sand waves varies. We compare our results to literature of the same sand wave areas, in which we find similar migration rates, and different wavelengths. By formulating four indicators, recommendations are made for the resurvey policy on the Belgian and Netherlands Continental Shelf. These indicators follow from the estimates for sea floor dynamics. We present a concept for the shallowest likely depth surface, on which we base two of the indicators. The other two indicators act as a warning: they quantify the potentially missed dynamics, which makes the procedure more robust in case of complicated morphology. We show clear differences in recommended resurvey frequency between the five analyzed regions. We conclude that the designed method is able to use a time series of bathy-metric surveys for the estimation of sea floor dynamics in a satisfactory way. Those dynamics may be present on the scale of the sea floor, it may be a local effect, or it may be due to a tidal sand wave pattern. Also, the results are successfully reduced to a set of four indicators, used to improve a resurvey policy. Based on these conclusions, we formulate recommendations on the extrapolation of the results in space and time, on potential adaptations to the designed procedure, and on implementation of the procedure. Note de contenu : Preface 1 Introduction 1.1 Nautical charting 1.2 Survey plan design 1.3 Detection of sea floor dynamics 1.4 Tidal sand waves 1.5 The uncertainty of depth measurements 1.6 Problem formulation 1.7 Research question and subquestions 1.8 Research strategy and outline 2 Bathymetric applications of Geostatistics 2.1 Introduction 2.2 Depth as a trend and its residuals 2.3 Covariance functions 2.4 Kriging 2.5 Conclusion 3 Estimating sea floor dynamics 3.1 Introduction 3.2 The method for the estimation of sea floor dynamics 3.3 Specification of a test scenario 3.4 Analysis results of a dynamic sea floor 3.5 Discussion 3.6 Conclusion 3.A Error characteristics 3.B Transformation of the sand wave parameters 3.C The application of statistical estimation and testing 4 The analysis of migrating tidal sand waves 4.1 Introduction 4.2 The application of deformation analysis 4.3 Results of the deformation analysis 4.4 Discussion of results 4.5 Conclusion 4.A Overview of used surveys 4.B Quantification of measurement errors 4.B.1 Covariance function of the error 4.B.2 Variances of the SEES surveys 4.B.3 Variances of the MBES survey 5 Spatial variations in sea floor dynamics 5.1 Introduction 5.2 Deformation analysis 5.3 The Selected Track region: little dynamics 5.4 The Noordhinder region: comparison with other methods 5.5 The region West of IJmuiden: sand wave migration 5.6 The region North of Terschelling: a flat sea floor 5.7 Discussion 5.8 Conclusion 5.A Overview of used surveys 6 Application to the resurvey policy 6.1 Introduction 6.2 Background: Hydrographic practice 6.3 Method: indicators of sea floor dynamics Numéro de notice : 15495 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : sans Accessibilité hors numérique : Non accessible via le SUDOC En ligne : https://www.ncgeo.nl/downloads/69Dorst.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62737

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Geostastical modeling of sedimentological parameters using multi-scale terrain variables: application along the Belgian part of the North sea / Els Verfaillie in International journal of geographical information science IJGIS, vol 23 n° 1-2 (january 2009)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 23 n° 1-2 (january 2009) . - pp 135 - 150 Titre : Geostastical modeling of sedimentological parameters using multi-scale terrain variables: application along the Belgian part of the North sea Type de document : Article/Communication Auteurs : Els Verfaillie, Auteur ; I. Du Four, Auteur ; et al., Auteur Année de publication : 2009 Article en page(s) : pp 135 - 150 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] Belgique [Termes IGN] données multisources [Termes IGN] écosystème [Termes IGN] habitat animal [Termes IGN] krigeage [Termes IGN] modèle numérique bathymétrique [Termes IGN] modélisation spatio-temporelle [Termes IGN] Nord, mer du [Termes IGN] représentation multiple [Termes IGN] sédiment Résumé : (Auteur) In the nowadays highly pressurized marine environment, a science-based approach to management becomes increasingly important. In many cases, the sediment nature and processes are the key to the understanding of the marine ecosystem, and can explain particularly the presence of soft-substrata habitats. For predictions of the occurrence of species and habitats, detailed sedimentological information is required. This paper presents a methodology to create high quality sedimentological data grids of grain-size fractions and the percentage of silt-clay. Based on a multibeam bathymetry terrain model, multiple sources of secondary information (multi-scale terrain variables) were derived. Through the use of the geostatistical technique, Kriging with an external drift (KED), this secondary information was used to assist in the interpolation of the sedimentological data. For comparison purposes, the more commonly used Ordinary Kriging technique was also applied. Validation indices indicated that KED gave better results for all of the maps. Copyright Taylor & Francis Numéro de notice : A2009-130 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1080/13658810802184135 En ligne : https://doi.org/10.1080/13658810802184135 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29760 [article]

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Regional gravity field modeling using airborne gravimetry data / Bas Alberts (2009)  

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Aspects of generating precise digital terrain models in the Wadden Sea from lidar-water classification and structure line extraction / A. Brzank in ISPRS Journal of photogrammetry and remote sensing, vol 63 n° 5 (September - October 2008)  

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Wind resource assessment from C-band SAR / M.B. Christiansen in Remote sensing of environment, vol 105 n° 1 (15/11/2006)  

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SeaWIFS discrimination of harmful algal bloom evolution / P.I. Miller in International Journal of Remote Sensing IJRS, vol 27 n° 11 (June 2006)  

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L'Allemagne et ses polders / L. Goeldner-Gianella (2000)

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A system analysis of salt marsh development along the mainland coast of the Dutch Wadden Sea / Brigit Janssen-Stelder (2000)

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Sea surface determination with respect to European Vertical Datums / L. Fenoglio-Marc (1996)

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Analysis of Thematic Mapper data for studying the suspended matter distribution in the coastal area of the German bight (North sea) / R. Doerffer in Remote sensing of environment, vol 28 n° 1 (April - June 1989)  

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Circulation patterns in AVHRR imagery / R.A. Vaughan in International Journal of Remote Sensing IJRS, vol 9 n° 4 (April 1988)  

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NavGrav, navigation and gravimetric experiment, at the North Sea / R.H.N. Haagmans (1988)  

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