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Sea surface topography and marine geoid by airborne laser altimetry and shipborne ultrasound altimetry / Philippe Limpach (2010)
Titre : Sea surface topography and marine geoid by airborne laser altimetry and shipborne ultrasound altimetry Type de document : Thèse/HDR Auteurs : Philippe Limpach, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2010 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 80 Importance : 208 p. Format : 20 x 30 cm ISBN/ISSN/EAN : 978-3-908440-24-6 Note générale : Bibliographie
Doctoral thesisLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] anomalie de pesanteur
[Termes IGN] bathymétrie acoustique
[Termes IGN] Crète (île)
[Termes IGN] données Jason
[Termes IGN] Egée, mer
[Termes IGN] géoïde altimétrique
[Termes IGN] géoïde local
[Termes IGN] geoïde marin
[Termes IGN] géoréférencement direct
[Termes IGN] GPS en mode cinématique
[Termes IGN] GPS en mode différentiel
[Termes IGN] océanographie dynamique
[Termes IGN] relief de la surface de la mer
[Termes IGN] sondage acoustique
[Termes IGN] surface de la mer
[Termes IGN] télémétrie laser aéroporté
[Termes IGN] validation des donnéesIndex. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) The aim of this project was to contribute to the improvement of sea level monitoring and to provide local-scale information on the short-wavelength structure of the marine gravity field, by developing enhanced methods for offshore sea surface height observations. The methods include airborne laser altimetry, shipborne ultrasound altimetry and GPS-equipped buoys. In a first step, instrumental aspects of sea surface height observations by airborne and shipborne altimetry were analyzed. Precise position and attitude of the range sensor are crucial for an accurate sea surface height computation. For this purpose, the survey aircraft and boat were equipped with a multi-antenna GPS array and inertial systems. Sea surface heights were computed from the range data by direct georeferencing. Important aspects are the influences of errors in the differential kinematic GPS positioning and in the attitude determination, as well as the calibration of boresight misalignments. In a second step, the obtained sea surface heights were reduced to mean sea surface by applying corrections for geophysical effects, including waves, tides, atmospheric pressure and wind forcing.
In the framework of this work, several regional campaigns for sea surface height surveys based on airborne and shipborne altimetry were carried out in the Eastern Mediterranean Sea. Dedicated surveys, including deployments of GPS buoys, were performed along Jason-1 radar altimetry ground tracks. Airborne laser altimetry data was acquired along densely spaced flight tracks covering an area of 200 by 200km around the western part of the island of Crete, Greece, in the vicinity of the Hellenic Trench. The objective was the determination of a detailed regional geoid and sea surface topography model in the framework of the GAVDOS project, funded by the European Union. Furthermore, several shipborne campaigns for sea surface height observations were carried out in the North Aegean Sea, in the vicinity of the North Aegean Trough.
Based on the airborne and shipborne altimetry data, a high-resolution sea surface topography of the survey areas was computed, with an accuracy of better than 10 cm. Geoid undulations were derived from the sea surface heights by subtracting the mean dynamic ocean topography induced by oceanic currents. Around western Crete, the geoid obtained from airborne laser altimetry is characterized by very large gradients, with an average height difference of 20m along a distance of only 200km and maximum local gradients of 22 cm/km. These gradients are a clear indication for significant gravity effects caused by the bathymetry and the geodynamic system of the Hellenic Trench. In the survey area in the North Aegean Sea, the geoid obtained from shipborne altimetry shows a distinct depression of 1.5 m, indicating a connection with the bathymetry and the geodynamic features of the North Aegean Trough.
The high resolution and accuracy of the sea surface and geoid heights obtained were verified by comparisons with mean sea surface models from multi-mission satellite radar altimetry, as well as with global and regional geoid models. The reduction of the geoid heights for modeled mass effects of topography, bathymetry, marine sedimentary deposits and crust-mantle boundary revealed pronounced gravity anomalies related to the geodynamic processes in the survey areas.Note de contenu : 1 Introduction
1.1 Motivation and Goals
1.2 Geophysical Characteristics of the Eastern Mediterranean
1.3 Former Work by the GGL in Related Fields of Research
1.4 Research Tasks and Project Outline
2 Geoid, Sea Surface and Dynamic Ocean Topography
2.1 Introduction
2.2 Geoid
2.3 Mean Sea Surface
2.4 Sea Level Anomaly
2.5 Dynamic Ocean Topography
2.6 Permanent Tide
3 Geophysical Effects on Sea Surface Heights
3.1 Introduction
3.2 Ocean Waves
3.3 Tides
3.4 Atmospheric Pressure and Wind Forcing
4 Airborne Laser Altimetry
4.1 Introduction
4.2 Instumental Setup
4.3 Laser Ranging
4.4 Laser Backscatter from Sea Surface
5 Shipborne Ultrasound Altimetry
5.1 Introduction
5.2 Instrumental Setup
5.3 Ultrasound Ranging
5.4 Sensor Synchronization
6 Direct Georeferencing
6.1 Introduction
6.2 Basic Principle
6.3 Kinematic GPS Positioning
6.4 Multi-Antenna GPS Attitude Determination
6.5 Boresight Misalignment Calibration in Airborne Altimetry
7 Sea Surface Heights by Airborne Laser Altimetry around Western Crete
7.1 GAVDOS Airborne Laser Altimetry Campaign
7.2 Instantaneous Sea Surface Height Profiles
7.3 Sea Surface Height Corrections
7.4 Repeatability Analysis
7.5 Time-Independent Sea Surface Topography
8 Sea Surface Heights by Shipborne Ultrasound Altimetry in the North Aegean Sea
8.1 Shipborne Ultrasound Altimetry Campaigns
8.2 Instantaneous Sea Surface Height Profiles
8.3 Sea Surface Height Corrections
8.4 Repeatability Analysis
8.5 Time-Independent Sea Surface Topography
9 Validation of Satellite Radar Altimetry Data
9.1 Introduction
9.2 Validation of Jason-1 Data with Airborne Laser Altimetry
9.3 Validation of Mean Sea Surface from Radar Altimetry
10 Geoscientific Exploitation of Airborne Altimetry Data around Western Crete
10.1 Marine Geoid, Gravity Anomalies and Deflections of the Vertical from Sea Surface Heights
10.2 Local Altimetric Geoid vs. Existing Models
10.3 Mean Dynamic Topography Estimation
10.4 Modeled Mass Effects on Geoid Heights and Gravity
10.5 Mass Reduction of Local Altimetric Geoid
11 Geoscientific Exploitation of Shipborne Altimetry Data in the North Aegean Sea
11.1 Marine Geoid, Gravity Anomalies and Deflections of the Vertical from Sea Surface Heights
11.2 Local Altimetric Geoid vs. Existing Models
11.3 Mean Dynamic Topography Estimation
11.4 Modeled Mass Effects on Geoid Heights and Gravity
11.5 Mass Reduction of Local Altimetric Geoid
12 Summary and ConclusionsNuméro de notice : 10369 Affiliation des auteurs : non IGN Autre URL associée : URL ETH Zurich Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.3929/ethz-a-005876550 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-80.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62408 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 10369-01 30.83 Livre Centre de documentation Géodésie Disponible