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Métadonnées de grilles au Service de géodésie et nivellement / Samuel Branchu (2009)

Public Titre : Métadonnées de grilles au Service de géodésie et nivellement Type de document : Monographie Auteurs : Samuel Branchu, Auteur Editeur : Paris : Institut Géographique National - IGN (1940-2007) Année de publication : 2009 Collection : Publications techniques en géodésie Sous-collection : Notes techniques num. 28215 Importance : 11 p. Format : 21 x 30 cm Langues : Français (fre) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] CIRCE [Termes IGN] coordonnées géographiques [Termes IGN] grille [Termes IGN] métadonnées [Termes IGN] nivellement indirect [Termes IGN] spécification de produit Index. décimale : 30.50 Nivellement - généralités Résumé : (Auteur) Ce document décrit les métadonnées de grilles au Service de la Géodésie et du Nivellement. Numéro de notice : 15407 Affiliation des auteurs : IGN (1940-2011) Thématique : POSITIONNEMENT Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=37884

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15407-02	30.50	Livre	Centre de documentation	Géodésie	Disponible
15407-01	30.50	Livre	Centre de documentation	Géodésie	Disponible
15407-03	7D	Livre	SGM	K001	Exclu du prêt

Aufbau der neuen Landesvermessung der Schweiz 'LV95'. Teil 12 Landeshöhennetz 'LHN95' / A. Schlatter (2007)

Public Titre : Aufbau der neuen Landesvermessung der Schweiz 'LV95'. Teil 12 Landeshöhennetz 'LHN95' : Konzept, Referenzsystem, kinematische Gesamtausgleichung und Bezug zum Landesnivellement 'LN02' Titre original : [Construction des nouveaux levers topographiques de la Suisse LV95. Partie 12 Réseau altimétrique national LHN95 : conception, système de référence, compensation cinématique d'ensemble et référence pour le nivellement national LN02] Type de document : Monographie Auteurs : A. Schlatter, Auteur ; Urs Marti, Auteur Editeur : Wabern : Office Fédéral de Topographie Swisstopo Année de publication : 2007 Collection : Swisstopo Doku num. 20 Importance : 215 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-302-10002-9 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Termes IGN] altitude orthométrique [Termes IGN] analyse comparative [Termes IGN] cote géopotentielle [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] géoïde local [Termes IGN] GPS en mode cinématique [Termes IGN] nivellement direct [Termes IGN] réseau altimétrique national [Termes IGN] Suisse [Termes IGN] système de référence altimétrique [Termes IGN] transformation de coordonnées [Vedettes matières IGN] Altimétrie Index. décimale : 30.50 Nivellement - généralités Résumé : (Documentaliste) Ce document s'appuie sur le travail de M. Schlatter concernant le réseau altimétrique suisse. Après une présentation du système altimétrique, il fait un rappel historique sur les techniques utilisées pour établir le réseau de nivellement local. Ensuite sont développées les techniques géodésiques d'aujourd'hui qui permettent une plus grande précision. Positionnement cinématique, déformations verticales de la croûte terrestre, potentiel de pesanteur sont combinés pour modéliser un nouveau réseau. Note de contenu : 1 Einleitung, Zielsetzungen und Projekt 1.1 Bedeutung moderner Höhenbestimmung und -Systeme 1.2 Zusammenhang mit der neuen Landesvermessung der Schweiz LV95 1.3 Aufbau der Dokumentation 1.4 Das'Projekt LHN951 2 Höhensysteme und Höhenrahmen 2.1 Referenzsysteme und -rahmen 2.2 Höhenbezugsflächen für die Lage- und Höhenbestimmung 2.3 Höhenarten 2.4 Definition eines Höhenreferenzsystems 2.5 Die Realisierung eines Höhenreferenzrahmens 2.6 Zusammenfassung und Vergleich der Höhensysteme 3 Höhenmessverfahren und ihr Bezug zu den Höhenrahmen 3.1 Das geometrische Nivellement 3.2 Die trigonometrische Höhenbestimmung 3.3 Satellitenmessverfahren 3.4 Photogrammetrie und Laseraltimetrie 3.5 Die barometrische Höhenbestimmung (Hypsometrie) 3.6 Messgenauigkeit und Höhenart: eine Grobübersicht 4 Konzept und Grunddaten zur Festlegung 'des neuen Landeshöhennetzes LHN95 4.1 Einleitung 4.2 Die Definition der Höhensysteme in LV95 4.3 Der Bezug zu den internationalen Höhensystemen 4.4 Das Konzept zur Realisation der Höhenreferenzrahmen in LV95 4.5 Die Grunddaten 5 Kinematische Ausgleichung der Landesnivellement-Messungen und Berechnung der geopotentiellen Koten 5.1 Einleitung 5.2 Ablaufschema zur Berechnung der geopotentiellen Koten der Hauptpunkte 5.3 Berechnung der beobachteten Potentialdifferenzen und Reduktion auf die Hauptpunkte 5.4 Das Modell der kinematischen Ausgleichung 5.5 Gewichtung der einzelnen Messungen und Lagerung der Ausgleichung 5.6 Die Schleifenschlüsse des Landesnivellements 5.7 Die Hauptresultate der kinematischen Ausgleichung 6 Rezente vertikale Bewegungen 6.1 Einleitung 6.2 Möglichkeiten und Grenzen des Präzisionsnivellements 6.3 Diskrete Einzelresultate und das Modell der rezenten vertikalen Bewegungen in der Schweiz 6.4 Der Einfluss der rezenten Höhenänderungen auf die Höhenrahmen 7 Vom Potential zur orthometrischen Höhe: die Berechnung der mittleren Schwere 7.1 Einführung und verwendete Berechnungsprogramme 7.2 Die verwendeten Massen- und Dichtemodelle 7.3 Die Berechnung der mittleren Schwere in der Lotlinie 7.4 Interpolation von Oberflächenschweren 7.5 Einfluss der Massenmodelle auf die orthometrischen Höhen 7.6 Genauigkeitsabschätzungen zu den orthometrischen Höhen 7.7 Näherungsformeln und der Vergleich mit den strengen orthometrischen Höhen 7.8 Zusammenfassung und Ausblick 8 Kombinierte Ausgleichung von orthometrischen Höhen aus dem Nivellement, GPS-Höhen und Geoidmodell 8.1 Die Konsistenz der Höhen 8.2 Die Theorie zur kombinierten Ausgleichung von Nivellement, GPS und Geoid 8.3 Die GPS-Höhen aus den landesweiten Kampagnen und die Gesamtlösung CHTRF04 8.4 GPS/Nivellementpunkte der neuen Landesvermessung LV95 8.5 Die Inkonsistenzen im Geoidmodell CHGeo98 8.6 Das neue Geoidmodell CHGeo2004 als Grundlage für den konsistenten Höhenrahmen LHN95 9 Die definitive Festlegung des konsistenten Höhenbezugsrahmens LHN95 der neuen Landesvermessung der Schweiz LV95 9.1 Die grundlegenden Entscheide und Festlegungen 9.2 Die Realisierung des Höhenreferenzrahmens LHN95 9.3 Konzept zur Berechnung der orthometrischen Höhen LHN95 sämtlicher HFP1 9.4 Test an drei Linien des Landeshöhennetzes 9.5 Der Vergleich mit den europäischen Höhenreferenzrahmen 9.6 Die Horizontunterschiede zu den Nachbarländern 10 Die Modellierung des Überganges LHN95 LN02 10.1 Einleitung und Definition der 'Spanne' als Unterschied zwischen den Höhenrahmen LHN95 und LN02 10.2 Grunddaten für die Analyse der Höhenrahmen und Stützpunkte für die Transformation 10.3 Analyse der Zwänge im bestehenden Höhenrahmen LN02 10.4 Analyse der Differenzen unter den strengen Höhenarten und zu LN02 10.5 Die Realisierung der Transformation LHN95 LN02 10.6 Das Programm htrans 10.7 Testberechungen und Genauigkeitsuntersuchungen mit bestehenden Daten 11 Schlussbetrachtungen und Ausblick 11.1 Schlussbetrachtungen 11.2 Ausblick Literaturverzeichnis Numéro de notice : 15425 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62717

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Das neue Landeshöhennetz der Schweiz LHN95 / A. Schlatter (2007)  

Public Titre : Das neue Landeshöhennetz der Schweiz LHN95 Titre original : [Le nouveau réseau altimétrique national de la Suisse LHN95] Type de document : Rapport Auteurs : A. Schlatter, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2007 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 72 Importance : 373 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-16-1 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Termes IGN] altitude orthométrique [Termes IGN] cote géopotentielle [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] géoïde local [Termes IGN] GPS en mode cinématique [Termes IGN] infrastructure nationale des données localisées [Termes IGN] nivellement par GPS [Termes IGN] positionnement par GNSS [Termes IGN] réseau altimétrique national [Termes IGN] Suisse [Termes IGN] système de référence altimétrique [Termes IGN] transformation de coordonnées [Vedettes matières IGN] Altimétrie Index. décimale : 30.50 Nivellement - généralités Résumé : (Auteur) The present report describes the establishment of the new as well as the existing and historic geodetic bases for height determination in the Swiss national geodetic network. The report originated in close scientific cooperation with the Geodesy Division of the Swiss Federal Office of Topography (swiss-topo) in association with the definition of a new vertical reference system and its realization in the form of the new national height network LHN95. The report is structured in three parts, each of which is inseparable from the other, as is suggested by the sequential numbering of the chapters. Part 1 presents and highlights the significance of modern vertical systems, the correlation to the renewal of the geodetic network in Switzerland (LV95) and the basic theory of vertical systems, frames and observation methods. Part 2 is a historical summary of geodetic height determination in Switzerland. Chapter 4 begins with the first experiments in the 17th century for calculating the heights of the Alps in the scope of scientific research. The first large-scale maps based on strict geodetic principles, the construction of railroads and water works as well as the beginning of cadastral surveying called for exact height information. The Nivellement de Precision, carried out by the Swiss Geodetic Commission (SGC) in the years 1864 to 1891, was the first national height reference frame. Even, though the theory of rigorous height systems based on the gravity field was well known at the end of the 19th century, the so-called "usual" heights LN02, which are purely levelled heights, are until today still the basis of the official heights in Switzerland. Chapter 5 shows how the SGC heights found their way into cadastral surveying networks and the efforts that were undertaken in the 20th century to apply gravimetric corrections to the national levelling networks, and to calculate rigorous adjustments. At the end of the 1980s, the new satellite navigation system GPS allowed the observation of national geodetic networks with an unprecedented and unimagined precision. Furthermore, together with the existing gravity and levelling observations, the technical means were now available for carrying out an integrated geoid determination and establishing a modern, orthometric vertical reference system and the corresponding reference frame. As a part of the project for a new geodetic network in Switzerland, the new national vertical network LFIN95 is the result of these efforts which are described in Part 3. The definitions, the fundamental data and the concept for the realization of LHN95 are presented in Chapter 6. Besides the ellipsoidal GPS heights and the gravity models, the key part of the calculation of the new national heights is the kinematic adjustment of the national levelling network and the gravity observations. In Chapter 7 it is shown how recent crustal movements may be estimated in order to define a non-constrained vertical frame based on the century-old observation series of this vast amount of levelling data. These recent vertical height changes in the Earth's upper crust are of particular interest to geophysics. Chapter 8 is a short excursion into the broad field of neotectonics and isostasy. The main focus, besides a historical summary of the insights gained from precise levellings so far, is on the discrete results from the current kinematic adjustment, the derived models and their interpretation. A central concern for geodesists is to point out the general causes of movements among control points as well as the possibilities and limits of the observation and adjustment methods. In order to obtain orthometric heights from geopotential numbers, the mean gravity values along the plumb lines to the geoid must be known for the observed bench marks. Chapter 9 deals with the determination of these values and how they influence the accuracy of the orthometric heights. It is shown that throughout Switzerland the heights of the bench marks relative to the geostation in Zimmerwald may be calculated with accuracy better than 2 cm. The key significance of the new vertical reference frame LHN95, however, lies in the fact that by combining the ellipsoidal heights from the new geodetic network LV95 observed with GPS and the undulations from the new geoid model CHGeo2004, an optimal consistency between the GPS method and the traditional terrestrial height determination was obtained (Chapters 9 and 10). Therefore, the determination of heights in a rigorous vertical system (following potential theory) with accuracy to the cm is much more efficient using GPS methods than traditional terrestrial observations. In Chapter 10 the heights from LHN95 along the national border are compared to the heights of the neighboring countries, and the differences to the existing European vertical frames are shown. Since the change to the new vertical reference frame LHN95 has not yet been executed in official cadastral surveying, on which practically all spatial data in Switzerland are based, the modelling of the transition between LHN95 and LN02 is of a decisive significance. Otherwise, the advantages of LHN95 for an efficient height determination with GPS would be completely in vain. Chapter 12 documents in detail the differences between and the origins of the two systems which are ranging from -25 cm and +65 cm. The algorithm used in the software program htrans to allow an appropriate transformation between the two vertical frames of the national geodetic control is explained and tested. The accuracy of the method is limited by the local distortions of the vertical reference frame LN02. It varies between a few millimeters along the levelling lines themselves and up to decimeters in between. Note de contenu : Teil I 1. Einführung 1.1 Hintergrund und Vorarbeiten 1.2 Bedeutung moderner Höhenbestimmung und-Systeme 1.3 Zusammenhang mit der neuen Landesvermessung der Schweiz LV95 1.4 Aufbau und Zielsetzung der Arbeit 2. Höhensysteme und Höhenrahmen 2.1 Referenzsysteme und -rahmen 2.2 Höhenbezugsflächen für die Lage- und Höhenbestimmung 2.3 Höhenarten. 2.4 Definition eines Höhenreferenzsystems. 2.5 Die Realisierung eines Höhenreferenzrahmens 2.6 Zusammenfassung und Vergleich der Höhensysteme 3. Höhenmessverfahren und ihr Bezug zu den Höhenrahmen 3.1 Das geometrische Nivellement 3.2 Die trigonometrische Höhenbestimmung 3.3 Satellitenmessverfahren 3.4 Photogrammetrie und Laseraltimetrie. 3.5 Die barometrische Höhenbestimmung (Hypsometrie) 3.6 Messgenauigkeit und Höhenart: eine Grobübersicht. Teil II 4. Erste Höhenbestimmungen in der Schweiz37 4.1 Arbeiten im 17. und 18. Jahrhundert: Die Höhenbestimmung der Alpenpioniere und die höchste Erhebung der Alpen. 4.2 Die Übergangsperiode 1785 - 1830: erste grossflächige Vermessungen und trigonometrisch abgeleitete Höhen 4.3 Die Höhen als Bestandteil der geodätischen Grundlagen für die Dufourkarte und die ersten Horizontfestlegungen 4.4 Das 'Nivellement de Precision 1864-91' der SGK 4.5 Übersicht über die Herkunft und die Bedeutung der historischen und aktuellen Horizontfestlegungen am Repere Pierre du Niton 5. Höhenbestimmung als Aufgabe der Landes- und der amtlichen Vermessung in der Schweiz 5.1 Das Versicherungsnivellement von 1893 - 1902 5.2 Der neue Horizont des RPN, das Landesnivellement und die Festlegung der Gebrauchshöhen LN02 5.3 Flächendeckende Höhen durch die amtliche Vermessung 5.4 Historischen Arbeiten zur Reduktion und zur gesamthaften Ausgleichung der Landesnivellementmessungen Teil III. 6. Konzept und Grunddaten zur Festlegung des neuen Landeshöhennetzes LHN95. 6.1 Einleitung 6.2 Die Definition der Höhensysteme in LV95 6.3 Der Bezug zu den internationalen Höhensystemen. 6.4 Das Konzept zur Realisation der Höhenreferenzrahmen in LV95. 6.5 Die Grunddaten 7. Kinematische Ausgleichung der Landesnivellement-Messungen und Berechnung der geopotentiellen Koten, 7.1 Einleitung 7.2 Ablaufschema zur Berechnung der geopotentiellen Koten der Hauptpunkte 7.3 Berechnung der beobachteten Potentialdifferenzen und Reduktion auf die Hauptpunkte 7.4 Das Modell der kinematischen Ausgleichung 7.5 Gewichtung der einzelnen Messungen und Lagerung der Ausgleichung. 7.6 Die Schleifenschlüsse des Landesnivellements 7.7 Die Hauptresultate der kinematischen Ausgleichung 8. Rezente vertikale Bewegungen und geophysikalische Interpretation 8.1 Einleitung 8.2 Einige Definitionen und Begriffserklärungen zu geodynamischen Prozessen. 8.3 Ursachen rezenter vertikaler Punktbewegungen 8.4 Möglichkeiten und Grenzen des Präzisionsnivellements 8.5 Bisherige Arbeiten in der Schweiz zur Bestimmung rezenter vertikaler Bewegungen mit Präzisionsnivellements 8.6 Diskrete Einzelresultate und das Modell der rezenten vertikalen Bewegungen in der Schweiz 8.7 Versuch einer geophysikalischen Interpretation 8.8 Der Einfluss der rezenten Höhenänderungen auf die Höhenrahmen. 9. Vom Potential zur orthometrischen Höhe: die Berechnung der mittleren Schwere 9.1 Einführung und verwendete Berechnungsprogramme 9.2 Die verwendeten Massen-und Dichtemodelle 9.3 Die Berechnung der mittleren Schwere in der Lotlinie 9.4 Interpolation von Oberflächenschweren 9.5 Einfluss der Massenmodelle auf die orthometrischen Höhen 9.6 Genauigkeitsabschätzungen zu den orthometrischen Höhen. 9.7 Näherungsformeln und der Vergleich mit den strengen orthometrischen Höhen 9.8 Zusammenfassung und Ausblick 10. Kombinierte Ausgleichung von orthometrischen Höhen aus dem Nivellement, GPS-Höhen und Geoidmodell, . 25 10.1 Die Konsistenz der Höhen 10.2 Die Theorie zur kombinierten Ausgleichung von Nivellement, GPS und Geoid 10.3 Die GPS-Höhen aus den landesweiten Kampagnen und die Gesamtlösung CHTRF04 10.4 GPS/Nivellementpunkte der neuen Landesvermessung LV95 10.5 Die Inkonsistenzen im Geoidmodell CHGeo98 10.6 Das neue Geoidmodell CHGeo2004 als Grundlage für den konsistenten Höhenrahmen LHN95 11. Die definitive Festlegung des konsistenten Höhenbezugs-rahmens LHN95 der neuen Landesvermessung der Schweiz LV95 11.1 Die grundlegenden Entscheide und Festlegungen 11.2 Die Realisierung des Höhenreferenzrahmens LHN95 11.3 Konzept zur Berechnung der orthometrischen Höhen LHN95 sämtlicher HFP1 11.4 Test an drei Liniendes Landeshöhennetzes 11.5 Der Vergleich mit den europäischen Höhenreferenzrahmen 11.6 Die Horizontunterschiede zu den Nachbarländer. 12. Die Modellierung des Überganges LHN95 & LN02 12.1 Einleitung und Definition der 'Spanne' als Unterschied zwischen den Höhenrahmen LHN95 und LN02 12.2 Grunddaten für die Analyse der Höhenrahmen und Stützpunkte für die Transformation 12.3 Analyse der Zwänge im bestehenden Höhenrahmen LN02 12.4 Analyse der Differenzen unter den strengen Höhenarten und zu LN02 12.5 Die Realisierung der Transformation LHN95 <-> LN02 12.6 Das Programm HTRANS 12.7 Testberechungen und Genauigkeitsuntersuchungen mit bestehenden Daten. 13. Schlussbetrachtungen, Ausblick und Dank 13.1 Schlussbetrachtungen 13.2 Ausblick 13.3 Dank Numéro de notice : 15420 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport d'étude technique En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-72.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62715

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Recueil d'articles publiés sur le géoïde et le nivellement avec GPS de 1998 à 2004 / Henri Duquenne (2005)

Public Titre : Recueil d'articles publiés sur le géoïde et le nivellement avec GPS de 1998 à 2004 Type de document : Monographie Auteurs : Henri Duquenne (1948-2010) , Auteur Editeur : Paris : Institut Géographique National - IGN (1940-2007) Année de publication : 2005 Collection : Publications techniques en géodésie Sous-collection : Cours et conférences num. 28109 Importance : 36 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Nivellement [Termes IGN] analyse comparative [Termes IGN] champ de pesanteur terrestre [Termes IGN] conversion altimétrique [Termes IGN] géoïde gravimétrique [Termes IGN] gravimétrie aérienne [Termes IGN] nivellement par GPS [Termes IGN] Quasi-Géoïde Français 1998 Index. décimale : 30.50 Nivellement - généralités Numéro de notice : 18906 Affiliation des auteurs : IGN (1940-2011) Thématique : POSITIONNEMENT Nature : Recueil / ouvrage collectif Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=41575

Contient

• Processus de conversions altimétriques applicables en France / Henri Duquenne (01/06/2000)
• Merging a gravimetric model of the geoid with GPS-leveling data: an example in Belgium / Henri Duquenne (01/08/2004)  

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18906-01	30.50	Livre	Centre de documentation	Géodésie	Disponible
18906-02	7D	Livre	SGM	K001	Exclu du prêt

The influence of data quality on the detectability of sea-level height variations / K.I. Van Onselen (2000)  

Public Titre : The influence of data quality on the detectability of sea-level height variations Type de document : Thèse/HDR Auteurs : K.I. Van Onselen, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2000 Collection : Netherlands Geodetic Commission Publications on Geodesy Sous-collection : New series num. 49 Importance : 204 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-90-6132-273-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] marée océanique [Termes IGN] marégramme [Termes IGN] marégraphe [Termes IGN] niveau de la mer [Termes IGN] niveau moyen des mers [Termes IGN] qualité des données [Termes IGN] série temporelle [Termes IGN] variation [Vedettes matières IGN] Altimétrie Index. décimale : 30.50 Nivellement - généralités Résumé : (Auteur) For low-lying areas like the Netherlands, an over-increasing sea level can become a serious threat. This is especially true if sea level rise accelerates, e.g., due to greenhouse-gas induced warming. To anticipate potential troubles, it is important to have a good estimate of the expected behaviour of future sea levels. This requires an accurate description of the present-day sea level variation curve and of foreseeable changes in this "natural" pattern in the near future. These changes in the behaviour of future sea levels can be based, e.g., on models predicting global change, but this is beyond the scope of this thesis. Much simplified, sea level rise over the last century could be described by a linear regression line. Accelerations of this "natural" pattern have occurred if the slope value of the regression line increases, or higher order regression coefficients are required to describe the sea-level rise curve. The better the natural sea level variation curve (as has occurred over the last century) can be determined, the easier it will be to detect a significant divergence from this curve. The objective of this thesis is to determine how well patterns in sea level height variations can be detected, given the limited quality of the data available. The objective of this thesis requires long sea level height time series. Therefore, only tide gauge data has been used and altimetry sea level height series have not been considered. Tide gauges measure sea level heights relative to the tide gauge bench marks. Consequently, the resulting sea level height time series show both variations in absolute sea level and vertical movements of the tide gauge bench marks. By monitoring the height changes between the tide gauge bench marks and a stable reference height, these relative sea level heights can (in principle) be converted into absolute sea level changes. Unfortunately, locating a reference point which is truly stable over long time spans will be extremely difficult, if not impossible. How well a specific sea level variation pattern can be detected depends on the sea level variations them-selves, the quality of the tide gauge measurements and, if applicable, the quality ofgeodetic measurements used to connect the tide gauge bench marks in height. Based on existing literature, it has been tried to gain a clear understanding of these various aspects. Unfortunately, in the literature studied on processes which can influence relative sea-level heights, (almost) no mention is made of long-periodic processes (periods over 20 years), while analysis of tide gauge records shows that long-periodic fluctuations with significant amplitudes do occur in sea level height time series. Sea level heights as used in this thesis are annual mean sea levels. The quality of these annual mean values not only depends on the quality of the tide gauge measurements, but also on the frequency of these measurements. Not only the quality of state-of-the-art techniques is important, but also of tide gauges and measuring frequencies which were used in the past. Since estimating long-term sea level variation curves requires long sea level height series, historical measurements have to be used as well. In chapter 3, an overview is given of the measuring precision and systematic errors and limitations characteristic for the six tide gauge systems commonly used during the last century. Based on information available for Dutch tide gauges, an estimate is given of how much the quality of annual mean sea levels deteriorates if mean values arc based on, e.g., mean tide levels instead of on hourly measurements. If data for a number of tide gauges is available, a common sea level variation curve, e.g., applying to the Dutch coast, can be estimated. Since tide gauge measurements are relative to the local tide gauge bench mark, any vertical movements of the tide gauges relative to one another will have introduced inconsistencies between the individual time series. These inconsistencies reduce the quality of a common sea level variation curve based on these tide gauge series. As long as tide gauges experience only secular height movements relative to one another, the common oscillation pattern can still be discerned using techniques like svd. However, the slope of the estimated common variation curve is determined by the rate of vertical movements of the individual tide gauges. If tide gauges undergo vertical movements which vary in rate and over time, the common oscillation pattern will be affected as well. By relating all sea level height series to the same reference frame (e.g., nap) internal differences in relative sea level due to vertical movements of the tide gauge bench marks are removed from the data sets. Ideally, permanent monitoring of the tide gauge bench marks is applied. Nowadays, this can be achieved by means of tips. However, in the past height differences were usually based on spirit levelling. In chapter 6, the quality of three geodetic techniques, i.e., gps, gravimetry, and spirit levelling is described. In addition, limitations of these techniques when applied to monitoring height changes of tide gauge bench marks arc discussed. Since changes in local gravity represent both variations in mass and changes in station height, gravimetry is not well suited for determining height differences. Uncertainties in height differences obtained by GPS can be reduced to within 1 cm. However, the quality of these measurements might be less in harbor areas (e.g., due to signal interference). GPS has the advantage that it allows for permanent monitoring over large distances, but measurements are only available for the last few decades. Spirit leveling can produce high precision height differences (over short distances), but is time consuming and prone to systematic errors (especially over long distances). However, leveled height differences arc often the only type of height information available. In the past, tide gauge bench marks have (hopefully) been connected to a local reference frame. Between some neighboring local height datums, height differences have occasionally been obtained as well. However, only since the second European leveling network (UELN-73), the height difference between the continent of Europe and Scandinavia and Great Britain respectively is available. These height connections consist of only a single connection line and, consequently, errors in these height differences cannot be detected by testing. In chapter 8, an indirect method is introduced for connecting vertical datums, which results in dynamic height differences between the fundamental stations in the various height datum zones. An advantage of this method is that quality information (both precision and reliability) of the estimated height differences can dc determined as well. Unfortunately, a high quality potential coefficient model is required. As a result, only if a new model (to be obtained from the planned GOCR mission) becomes available, height differences between datum zones could be derived with standard deviations of 1 cm. The quality of sea level variation curves depends on the method used to estimate these curves. A number of data analysing techniques have been tested for their suitability for working with sea level height data. Sea level height time series have a number of specific characteristics, for instance non-stationarity, data quality which is not constant for the complete time series, and a wide range of periodic fluctuations with sometimes variable frequencies and amplitudes. As a result, most of the techniques examined do not work well when applied to sea level height data. It is found that the best techniques for smoothing sea level height series are moving average smoothing and Singular Spectrum Analysis, while estimates of future sea level heights should be based on cither AR(i)MA modelling or regression. To determine how well specific sea level variation patterns can be detected, experiments with a large variety of simulated sea level height time series have been performed. These simulated time series consist of the curve which needs to be detected (e.g., a linear trend), periodic fluctuations (based on actual tide gauge data) and simulated additional errors. This can cither be inaccuracies introduced by the tide gauge equipment or the height measurements, or (uncorrected for) height variations between tide gauge bench marks. By applying regression to the simulated time series, it is examined whether or not the original sea level variation curve can be recovered. It should be noted that statistical significance of estimated regression coefficients is no guarantee that the "true" sea level variation curve is detected. For example, if linear regression is applied to a sea level series following a quadratic curve, the estimated trend value can still be statistically significant. For this reason, often trend estimates are shown as a function of an increasing number of observations. For the above mentioned example, estimated trend values will steadily increase with an increasing number of included observations. Only if the model (of a linear regression line) fits the data, and if enough observations are available, estimated trend values will stabilise around the trend value actually present in the data set. First, experiments have been performed with sea level height data for a single tide gauge. In this case, the original data relative to the tide gauge bench mark can be used. If (based on external knowledge of the behavior of the local sea level) long-periodic fluctuations could be eliminated from the data set, the detectability of a single linear regression line depends on the trend value and the noise level of the measurements. For sea level data with a trend of 1.5 mm/yr, even if a noise level of 5 cm applies, this trend can be detected if 35 observations are available. If a simulated time series contains long-periodic fluctuations based on data for tide gauge Den Helder, of the order of 90 years of observations are required before trend estimates stabilise around the actual trend value on which the data set is based. Therefore, it is concluded that long-periodic fluctuations are the main factor in determining the amount of data required to detect a linear trend in a sea level height time series. In chapter 7, using six tide gauge data sets, a common sea level variation curve for the Dutch coast is estimated. In order to eliminate deviations from this common curve caused by height variations of the tide gauge bench marks relative to one another, all tide gauges have to be connected in height to the local reference system (nap). Inaccuracies in the required height connections introduce inconsistencies between the time series. Since the actual height connection history for the tide gauges is unknown, a number of scenarios have been used to simulate height connection errors. Experiments show that the quality of the estimated common variation curve not only depends on the precision of the height measurements, but also on the time span between subsequent height connections. For higher levels of connection noise, it is more pronounced that the larger the time span between subsequent connections, the less dependable the estimated trend values will be. In order to detect future sea level rise accelerations, historical data has to be used as well. Experiments show that, if long periods have elapsed between historic height connections, the precision of future height connections is of almost no importance. Increasing the standard deviation of future height measurements from 5 mm to 2 cm, or increasing the time span between height connections from one to 10 years, hardly influences the results. Finally, for the North Sea area, the quality of spatial variation patterns which can be derived based on trend values for 18 tide gauges, is examined. A spatial pattern in sea level height variations should be based on real differences in trend values for the various locations and not on variations resulting from measuring errors and height changes between tide gauge bench marks. Based on experiments with simulated time series, the following conclusions have been made. If height connections to a local reference frame are performed every 10 years, ranges of errors in trend estimates (as a function of latitude and longitude) are three times as large as results based on annual connection of heights. As a result of, e.g., post-glacial rebound, fundamental stations in the different datum zones can experience height changes relative to one another. If the individual time series (connected to the local datums) are not corrected for these relative vertical movements, this will result in large errors in the estimated spatial variation pattern. If height differences between vertical datum zones are based on results derived for European leveling networks, resulting errors in trend values (as a function of latitude and longitude) will be much larger than those caused by the post-glacial rebound movements (of the selected fundamental stations: Amsterdam, Newlyn, and Helsingborg) itself. This same holds for differences in vertical movements obtained by GPS measurements with a standard deviation of the order of 1 mm/yr. Note de contenu : 1 INTRODUCTION Sea-level variations Objectives of this thesis Outline 2 TIDE GAUGE MEASUREMENTS Introduction Error characteristics of tide gauge instruments Sampling rate and averaging method of tide gauge readings Conclusions and recommendations 3 TECHNIQUES FOR ANALYSING SEA-LEVEL DATA Introduction Smoothing of tide gauge data Prediction of future sea levels Sea-level data for a group of tide gauges Conclusions and recommendations 4 DETECTABILITY OF CURVES IN RELATIVE SEA LEVEL Introduction Estimating curves in individual time series General structure of simulated data sets " Ideal " measurement series Time series containing short-periodic fluctuations Time series containing short- and long periodic fluctuations Conclusions and recommendations 5 CONNECTING TIDE GAUGES TO A LOCAL HEIGHT SYSTEM Introduction Problems related to the different " height " systems Error characteristics of measuring techniques Selection of observation sites Required sampling and time span of measurements 6 DETECTABILITY OF CURVES IN SEA LEVEL RELATIVE TO A LOCAL DATUM Introduction General structure of simulated data sets Same trend throughout the time series Transition to higher trend at the beginning of the time series Transition to higher trend at the end of the time series Conclusions and recommendations 7 REGIONAL HEIGHT DATUM CONNECTION Introduction Adding datum shifts to a geodetic boundary value problem Least squares solution of a vertical datum connection A-priori covariance matrices Datum connection in North-West Europe " Ideal " cap size for terrestrial gravity measurements Influence of the number of stations Conclusions and recommendations 8 SEA-LEVEL VARIATION PATTERNS Introduction General structure of simulated data sets Inconsistencies in annual mean values Inconsistencies introduced by local height connections Height datums experience linear movements Vertical datum connection Conclusions and recommendations 9 CONCLUSIONS AND RECOMMENDATIONS Conclusions General remarks concerning sea-level monitoring Recommendations for future research A Information concerning tide gauge stations B Derivations C Additionnal information concerning common variations curves Numéro de notice : 11431 Affiliation des auteurs : non IGN Autre URL associée : Complément Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : sans En ligne : https://www.ncgeo.nl/downloads/49VanOnselen_1.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54405

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
11431-01	30.50	Livre	Centre de documentation	Géodésie	Disponible

Direct access to the French digital height databank via minitel / Michel Le Pape (1999)

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Final results of the Baltic Sea level 1997 GPS campaign / Markku Poutanen (1999)

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Determination of orthometric heights using GPS levelling / Markku Ollikainen (1997)

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Active fault line search in southern and central Finland with precise levellings / P. Lehmuskoski (1996)

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Projets de spécifications produit du nivellement de référence français / Henri Duquenne (1996)

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Final results of the Baltic Sea level 1993 GPS campaign / J. Kakkuri (1995)

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CNIG groupe de travail "Réseaux de nivellement" / Conseil national de l'information géographique (1994)

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Final results of the Baltic Sea level 1990 GPS campaign / J. Kakkuri (1994)

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Laser-Profilmessungen zur topographischen Geländeaufnahme / Joachim Lindenberger (1993)  

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Réseau français de nivellement scientifique / Jean-Paul Nicolas (1993)

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