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Identification and modelling of sea level change contributors on GRACE satellite gravity data and their applications to climate monitoring / Bert Wouters (2010)  

Public Titre : Identification and modelling of sea level change contributors on GRACE satellite gravity data and their applications to climate monitoring Type de document : Rapport Auteurs : Bert Wouters, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2010 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 73 Importance : 182 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-316-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] champ de pesanteur terrestre [Termes IGN] changement climatique [Termes IGN] GRACE [Termes IGN] Groenland [Termes IGN] niveau moyen des mers [Termes IGN] surveillance météorologique Index. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) Recently, the Intergovernmental Panel on Climate Change named sea level rise as one of the major challenges of the 21st century. Given the high population density of coastal regions, a small rise of the sea level will have a substantial impact on human society. However, the Earth's climate system is a complex matter arid model predictions of the sea level changes likely to be expected in the coming century currently show a wide spread. Clearly, a thorough understanding of present-day climate variability is imperative narrow this uncertainty band, which on its turn depends on the availability of accurate and detailed observations of our climate. A valuable contribution to the expanding array of satellites dedicated to observations of the Earth System, are the Gravity Recovery and Climate Experiment (GRACE) satellites, launched in March 2002. This mission is dedicated to observing changes of the Earth's gravity field at (sub-)monthly intervals. At time-scales of a few years, these changes are mostly related to the redistribution of water on the Earth's surface. For example, a thinning of the Greenland ice sheet will manifest itself as a local negative anomaly in the gravity field, whereas the water that is added to the ocean will show up as a predominantly positive anomaly. The main objective of this dissertation is to study how the GRACE observations can be used to improve our knowledge of changes in the Earth's climate systems, and how the data should be processed in order to optimize quality and spatial resolution. The GRACE data provided by the science teams consist of spherical harmonic coefficients. They show particular correlations between coefficients of identical order and even and odd degree, respectively, due to the mission's architecture and deficiencies in the background models used throughout the processing of the satellite measurements. These noise artifacts show up as striping patterns along the north-south direction in the monthly maps of surface mass changes, hampering the interpretation of the observations. In this dissertation, it is shown that empirical orthogonal function (EOF) analysis is an effective method to reduce the noise in the GRACE data. This statistical tool separates a data set into a number of characteristic (eigen) modes of variance, in combination with an index describing the amplitude of the mode in time, i.e. the principal components. The EOF analysis can be applied to the maps of surface mass changes, in which case the first few modes are related to the annual and long-term trend components. The fourth mode appears to be related to the El Nino/Southern Oscillation. The noise signals arc absorbed by the higher modes, which makes the leading modes largely stripe-free up to a resolution of approximately 400 kilometers. A further reduction of the noise can be obtained by applying the EOF de-composition directly to the spherical harmonic coefficients, after grouping them following order. The principal components arc compared to a random process and, if the two arc statistically sufficiently alike, not used in the further data processing. A series of tests shows that this approach reduces the noise by 60-80 %, compared the non-filtered case. An important feature of this filter is that it does not alter the shape of the signal and causes less reduction its power, compared to other commonly used filter methods based on the approach of Swenson and Walir (2006). Using the filtered data, changes in the mass content of the ocean have been studied. The GRACE satellites are capable of capturing seasonal changes in the ocean mass content accurately on a global scale. In combination with sea surface height observations made by satellite altimeter, the steric sea level component (related to changes in the heat and salinity content of the ocean) can be separated as well. A comparison with reference data sets shows that locally a coherent signal can be obtained at a (Gaussian) resolution of approximately 500 km over the oceans. These steric changes dominate the sea level in most of the oceans, but strong ocean bottom pressure fluctuations are observed in several areas, e.g., the Gulf of Carpentaria and the Gulf of Thailand. Estimates of long-term changes in the ocean mass and heat content arc a more challenging problem, and require a longer observation period and a better modeling of mass redistribution in the solid earth and the position of the center of mass of the Earth, two components to which the GRACE observations arc particularly sensitive. It is found that the global spherical harmonic coefficients contain more information than previously acknowledged. This is demonstrated by using the GRACE data to obtain a picture of the mass balance of the Greenland ice sheet at a regional scale. From the research in this dissertations, it shows that Greenland lost 179 Gigaton each year on average between 2003 and 2008, causing a global mean rise of sea level by 0.5 mm/yr. Comparing the trend in the first few to that in the last few years shows a speed-up of the thinning, which corroborates the picture of an increasingly negative mass balance of the ice sheet since the mid 1990's as indicated by, for example, regional climate models and radar altimetry observations. The majority of the losses occur in the coastal regions in the southeastern sector. The northwestern coastal zones were approximately in balance up to the summer of 2005, but show strong negative trends since. Large year-to-year differences in the mass balance of the ice sheet are observed, with a record loss in the warm summer of 2007. A strong correlation between the GRACE observations in summer and satellite measurements of surface melt area extent is demonstrated. Also, good agreement is found with regional climate modeling data, highlighting the potential of the GRACE observations to validate and improve the numerical models. A mass redistribution on land will cause a change in the shape of the global geoid. Sea level, when not acted upon by any other forcings, will adjust to this equipotential surface. Therefore, when water is exchanged between ocean and continents (and changes due to ocean dynamics are disregarded), sea level will not rise or fall uniformly, which is known as the so-called self-gravitation effect. Due to their global coverage, the GRACE observations of continental mass distribution are an excellent input to model this phenomenon. Strongest deviations from a uniform distribution are found off the coast of Alaska and in the Bay of Bengal, where differences of more than 100% are found on seasonal time-scales. In these regions, inclusion of the self-gravitation effect into numerical ocean model would result in a better agreement between modeled and observational data. From the work presented in this dissertation, it shows that the GRACE satellites are an invaluable tool for the monitoring of our climate system. Statistically filtering of the data reveals a wealth of information. In combination with altimetry observations, the GRACE data allows the separation of mass and steric components in sea level on seasonal time scales. Given a longer observational period and an improved understanding of the processes in the solid earth, expected to come available soon thanks to ESA's GOCE missions, long-term trends in these components will be identifiable. Furthermore, the GRACE mission allows us to put a constraint on the contribution of the Greenland ice sheet to present-day sea level rise. The technique to recover these changes can easily be expanded to other regions, such as the Antarctic or the Alaskan glacier fields. The synergy between GRACE data, future missions such as Cryosat-2, which will map height variations of the cryosphere with an unprecedented accuracy, and regional climate models, uncovering the physical processes behind the observed changes, promises a leap forward in our understanding of the mass balance of the ice sheets. Finally, com-paring the modeled deviations from uniform sea level changes with in-situ data such as from tide-gauges, may lead to a direct validation of the aforementioned self-gravitation theory with present-day data. Numéro de notice : 10335 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport de recherche DOI : sans En ligne : https://www.ncgeo.nl/downloads/73Wouters.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62396

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Sea surface topography and marine geoid by airborne laser altimetry and shipborne ultrasound altimetry / Philippe Limpach (2010)  

Public 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 thesis Langues : 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 données Index. 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 Conclusions Numéro 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

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GPS based dynamic monitoring of air polluants in the city of Zurich / Philippe Thomas Kehl (2009)  

Public Titre : GPS based dynamic monitoring of air polluants in the city of Zurich Type de document : Thèse/HDR Auteurs : Philippe Thomas Kehl, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2009 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 78 Importance : 155 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-22-2 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] changement climatique [Termes IGN] données spatiotemporelles [Termes IGN] polluant [Termes IGN] pollution atmosphérique [Termes IGN] positionnement par GPS [Termes IGN] surveillance écologique [Termes IGN] temps réel [Termes IGN] Zurich (Suisse) Index. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) Despite the decrease in road traffic emissions air pollutant concentrations of nitrogen dioxide, particulates and ozone often exceed the limit values at urban sites in Switzerland. This project aimed at providing a dynamic and real-time assessment of ambient air quality and at improving the understanding of the interaction between road traffic emissions and urban air quality. It is designed as a feasibility study for dynamic air-pollution measurements in the local scale. Three research topics were being pursued in this thesis : air quality monitoring, satellite based positioning (GPS) of a measurement system in an urban environment and the influence of road traffic emissions on the air quality in the city of Zurich. The data analysed are based on the autonomous operation of a measuring system on a tram in regular service. A dedicated measurement system was built to measure the concentrations of the three most relevant air pollutants in Zurich. These are nitrogen oxides (NO and NO2), aerosol particles (participate matter) and ozone (O3). Nitrogen oxides and ozone are measured using the standard techniques involving chemiluminescence of NO and UV absorption of O3, respectively. Particulates are measured using a diffusion charging particle sensor which suits the requirements for space, a short measurement period and resistance against vibrations. Furthermore meteorological parameters (temperature, humidity and pressure) were measured. The tram was equipped with the measurement system. During two measurement campaigns in spring/summer 2005 and winter/spring 2005/06 the tram travelled on three different tram tracks, which cross the city in north-south or east-west direction. They represent the various characteristics of an urban environment, such as busy places and parts of the city without private road traffic. The measurements were being transferred in real-time using mobile communication technologies (GSM, GPRS). A web site was being updated in real-time with the position of the tram on a map, the measurements and the operating state of the measurement system and its sensors. GPS was used for precise positioning and timing. Urban sites often degrade navigation accuracy and availability. Therefore, a suitable receiver was evaluated and techniques to provide precise and reliable positioning data were developed. The latter involves filtering and projective map-matching to exclude faulty positions and determine precise positions. Furthermore, standard position-time relations for the tram were determined to interpolate GPS outages, which last a few seconds up to a few dozens of seconds. A dispersion modelling study was carried out for a 3-3 krn2 area in the inner city of Zurich using a state-of-the art numerical dispersion model. This involved the models NEMO (emissions from traffic), GRAMM (meteorology) and GRAL (dispersion) from the Institute of Internal Combustion Engines and Thermodynamics of the Graz University of Technology. The feasibility of dynamic and real-time measurements and its limitations were shown by carrying out two measurement campaigns lasting 18 and 20 weeks in spring/summer 2005 and winter/spring 2005/06. The analysis of the measurements clearly show varying concentrations of air pollutants along the tram track as well as characteristic hot-spots at busy places. Note de contenu : 1 Introduction 2 Scientific Theory 2.1 Air pollution & emission sources 2.1.1 Nitrogen oxides 2.1.2 Ozone 2.1.3 Conversion between ppb and mass per volume units 2.1.4 Particulate matter 2.1.5 Smog 2.1.6 Ambient air quality standards and legislation 2.1.7 Air quality trends for Zurich 2.2 Global positioning system (GPS) 2.2.1 GPS constellation 2.2.2 Measurement principle 2.2.3 Sources of errors and accuracy 2.2.4 GPS in urban areas 2.2.5 Co-ordinate transformation 3 Measurement System 3.1 The measurement platform 3.2 The measurement system 3.3 Environmental sensors & measurement principles 3.3.1 Nitrogen oxides sensor 3.3.2 Ozone sensor 3.3.3 Particle sensor 3.3.4 Meteorological sensors 3.4 Positioning sensor & time reference 3.5 Power supply & control 3.6 Computer & data logger 3.7 Telemetry 4 Measurement Campaigns & Data Processing 4.1 Tram operation and tram lines 4.2 Measurement campaigns 4.2.1 Campaign #1 4.2.2 Campaign #2 4.2.3 Real-time visualisation of the measurements 4.3 Data post-processing 4.3.1 Database 4.3.2 Environmental measurements 4.3.3 GPS measurements 4.3.4 Map-matching and interpolation 4.3.5 Georeferencing 4.4 Permanent stations data 5 Data Analysis & Results 5.1 Overview over the available data 5.1.1 Raw time series 5.1.2 Daily mean values . 5.2 Data quality assessment 5.3 Data analysis & discussion . 5.3.1 Comparison of daily mean values 5.3.2 Comparison of monthly mean values 5.3.3 Limit value exceedances 5.3.4 Comparison of tram measurements at the UGZ permanent station 5.3.5 Summer 2005 5.3.6 Winter 2006 5.4 GPS performance analysis 6 Emission & Dispersion Modelling 6.1 Introduction 6.2 Modelling approach 6.3 Geometrical data 6.3.1 Topography (elevation model) 6.3.2 Buildings 6.4 Emission modelling 6.4.1 Overview 6.4.2 Input data 6.4.3 Results 6.5 Meteorological modelling (wind field simulations) . 6.5.1 Overview 6.5.2 Classification of weather situations 6.5.3 Calculation 6.5.4 Analysis 6.6 Dispersion modelling 6.6.1 Calculation 6.6.2 Results analysis 6.7 Comparison with measurements 6.7.1 Summer 2005 6.7.2 Comparison with the NABEL permanent station 6.7.3 Winter 2006 7 Conclusions Numéro de notice : 15513 Affiliation des auteurs : non IGN Autre URL associée : URL ETH Zurich Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.3929/ethz-a-005553378 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-78.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62746

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High-resolution GPS tomography in view of hydrological hazard assessment / Simon Lutz (2009)  

Public Titre : High-resolution GPS tomography in view of hydrological hazard assessment Type de document : Thèse/HDR Auteurs : Simon Lutz, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2009 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 76 Importance : 200 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-20-8 Note générale : Bibliographie Doctoral thesis Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] aérosol [Termes IGN] atmosphère terrestre [Termes IGN] Bernese [Termes IGN] campagne d'expérimentation [Termes IGN] collocation [Termes IGN] distribution spatiale [Termes IGN] double différence [Termes IGN] interpolation spatiale [Termes IGN] météorologie [Termes IGN] méthode des moindres carrés [Termes IGN] modèle atmosphérique [Termes IGN] prévision météorologique [Termes IGN] propagation troposphérique [Termes IGN] réfraction atmosphérique [Termes IGN] risque naturel [Termes IGN] temps réel [Termes IGN] teneur en vapeur d'eau [Termes IGN] tomographie [Termes IGN] traitement de données GNSS [Termes IGN] Valais (Suisse) [Termes IGN] vapeur d'eau [Termes IGN] voxel Index. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) In the last few years, the use of propagation delays of GNSS radio signals due to the atmospheric effect has gained considerable importance as a valuable contribution to numerical weather forecasting. GPS-based tomography is a dedicated method to resolve the temporal variation and spatial distribution of the most important constituent of the atmosphere, the tropospheric water vapor. The four-dimensional tomographic approach, however, has not yet been completely established. Investigations on the small-scale high-resolution configuration will now help to determine and model water vapor distribution and variation over local, mountainous catchment areas. Especially, the development towards near real-time analysis with a high update rate of less than one hour will reveal the potential in the field of short and medium range forecasts. Three main objectives were defined for this research project: The first objective was the study of the feasibility of GPS tomography in a small-scale and Alpine area. Furthermore, the processing of campaign-type measurements had to be considered specifically. The second aim was the determination of the four-dimensional distribution of atmospheric water vapor over a local region using GPS tomography in view of hydrological hazard assessment. Thirdly, aspects of real-time determination had to be investigated. In this context, it had to be accounted for that, instead of precise GNSS satellite orbits, predicted ones like broadcast ephemerides or ultra-rapid orbits had to be used. Also, it had to be addressed that the processing time is a critical issue in real-time computation. As a consequence, the parameters of the complete GPS processing were refined and adapted to near real-time applications. Furthermore, new algorithms in the tomographic software were to be designed and evaluated. The tomographic software package AWATOS (Atmospheric Water Vapor Tomography Software), developed at the Geodesy and Geodynamics Laboratory, ETH Zurich, was used for the assimilation of double-differenced GPS observations and interpolated meteorological data sets. The spatial distribution of water vapor can be determined by least-squares inversion with a high temporal resolution. The work was carried out in five steps: Simulations helped to design an optimal GPS network for the tomographic purpose. Based on these findings, two dedicated field campaigns were performed to study the feasibility of the method for a non-permanent densification network in an Alpine region in Switzerland. Secondly, GPS derived zenith total delays (ZTD) as well as double-differenced residuals were estimated using a high performance and high accuracy post-processing software package (Bernese GPS Software Version 5.0). The results were validated by comparison with independent methods. With the software package COMEDIE, meteorological data was collocated and interpolated for the separation of the total delays into a wet and a dry part. In the third step, this set of data was processed with the GPS tomography software package AWATOS to obtain spatially and temporally highly-resolved wet refractivity fields. An automatic generation of tomographic voxel models was developed in the forth step. This tool allows high flexibility in tomographic processing and forms a fundamental part of an adaptive method of choosing voxel models at a particular spatial resolution. In the fifth step, the aspects of near real-time processing were investigated. Measurements from a solar spectrometer and data from the current numerical weather model COSMO-7 of MeteoSwiss were available for comparison purposes. During the campaigns, radiosondes were launched to measure vertical profiles of the tropospheric meteorological components in situ and to validate the tomographic results. The success of the tomographic method was revealed by the statistical analyses. The wet refractivity profiles from the GPS tomography software package AWATOS in the high-resolution mode match the profiles derived from corresponding radiosonde measurements within 10 ppm (refractivity units). The AWATOS profiles represent the characteristics of the different tropospheric layers in most cases with high significance. The accuracy of GPS tomography in near real-time was assessed based on dedicated case studies with real-time orbits. The error budget of the near real-time calculations was compared to the best postprocessing solutions available. Due to large variations in the time series of the Up component of the GPS coordinate estimation, the broadcast ephemerides are not recommended for GPS meteorological applications. But ultra-rapid orbits, which are also available in real-time, yield satisfying results regarding tropospheric parameter estimation (ZTD) and the high-resolution GPS tomographic analysis. Note de contenu : 1 Introduction 1.1 Trends in GPS meteorology 1.2 Research review of atmospheric water vapor profiling 1.3 Significance of high-resolution GPS tomography 1.3.1 For the research community 1.3.2 For practical applications 1.4 Objectives 1.5 Structure 2 Theoretical background of GPS meteorology 2.1 Atmospheric water vapor 2.2 Radio wave refractivity 2.3 Refraction and path delay modeling 2.3.1 Definition 2.3.2 The Saastamoinen formula 2.3.3 Integrating tropospheric refractivity 2.3.4 Path delay interpolation with COITROPA 2.4 The Global Positioning System (GPS) 2.4.1 Introduction to GPS 2.4.2 The GPS observation equations 2.4.3 Mapping functions and standard models 2.4.4 Troposphere modeling in the Bernese GPS Software 2.5 The software package COMEDIE 2.5.1 4-D refractivity field from meteorological data 2.5.2 Estimation of tropospheric path delays 3 Ground-based GPS tomography of the neutral atmosphere 3.1 Models, methods and algorithms 3.1.1 The tomographic voxel model 3.1.2 The apriori model . 3.1.3 Inter-voxel constraints 3.1.4 Separation of the total path delay 3.2 The software package AWATOS 3.2.1 Double-difference GPS tomography 3.2.2 The tomographic equation system 3.2.3 Ray tracing and the design matrix 3.2.4 (Pscudo-) Observations and the weight matrix 3.2.5 Error budget 3.3 Network analysis tool 4 Outline of the two field campaigns 4.1 Introduction 4.2 The project area in the canton of Valais (Switzerland) 4.3 The July 2005 field campaign 4.3.1 GPS network 4.3.2 Meteorological ground measurement network 4.3.3 Radiosondes 4.4 The October 2005 field campaign 4.4.1 GPS Network 4.4.2 Meteorological ground measurement network 4.4.3 Radiosondes 4.4.4 Solar Spectrometry for comparison purpose 5 Data preprocessing 5.1 Introduction 5.2 GPS data processing 5.2.1 Overview 5.2.2 Criteria for fix station selection 5.2.3 Parameter settings in the Bernese GPS Software 5.2.4 Network solutions 5.2.5 Section summary 5.3 Meteorological data processing 5.4 Path delay comparison 6 The numerical weather model COSMO-7 6.1 Model description 6.2 Distribution of the available data 6.3 Data processing workflow 6.4 Data analysis 6.4.1 Comparison with balloon sounding profiles 6.4.2 Time series of integrated path delays 6.4.3 Comparison with time series of hourly GPS-ZTD 6.4.4 ZTD comparison with rainfall data 7 Enhancements of AWATOS 7.1 Introduction 7.2 New models and algorithms 7.2.1 Designing the voxel model 7.2.2 Obtaining a priori information 7.2.3 Allocation of meteorological data 7.2.4 Selection of beneficial stations 7.3 Further analysis tools 7.4 Notes on near real-tirnc analysis and predictive algorithms 7.5 Accuracy and reliability assessment 8 Results and discussion 8.1 Towards high spatial resolution 8.1.1 Impact of vertical spacing 8.1.2 Vertical resolution and cutoff elevation angle 8.1.3 Impact of horizontal spacing 8.1.4 Summary on the July 2005 campaign data 8.1.5 Summary on the October 2005 campaign data 8.1.6 Impact of a reduced network in October 2005 8.1.7 Discussion on spatial resolution 8.2 Correlation analysis with meteorological surface data 8.2.1 Comparison with air temperature 8.2.2 Wet refractivity variation and sunshine duration 8.2.3 Dew point temperature and atmospheric water vapor 8.3 Aspects of changing temporal resolution 8.4 Investigations in near real-time analysis 8.4.1 Processing real-time GPS orbits 8.4.2 Examination of time correlation strategies 9 Conclusions Numéro de notice : 15512 Affiliation des auteurs : non IGN Autre URL associée : URL ETH Zurich Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.3929/ethz-a-005648120 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-76.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62745

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15512-01	30.83	Livre	Centre de documentation	Géodésie	Disponible

Trajectory determination and analysis in sports by satellite and inertial navigation / Adrian Wägli (2009)  

Public Titre : Trajectory determination and analysis in sports by satellite and inertial navigation Type de document : Thèse/HDR Auteurs : Adrian Wägli, Auteur ; Jan Skaloud, Directeur de thèse Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2009 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 77 Importance : 173 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-20-5 Note générale : Bibliographie Doctoral thesis Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] filtrage du bruit [Termes IGN] GPS-INS [Termes IGN] modèle d'erreur [Termes IGN] navigation inertielle [Termes IGN] orientation [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] précision décimétrique [Termes IGN] sport [Termes IGN] test de performance [Termes IGN] trajectographie par GPS [Termes IGN] trajet (mobilité) Index. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) [Préface] The abundance and availability of small positioning devices offers new opportunities (and challenges) for the art and science of Kinematic Geodesy. Certainly, as the inventors of inertial navigation never dreamed of a full Inertial Measurement Units (IMUs) occupying space of few cubic millimeters, the designers of the Global Positioning System (GPS) never thought of placing miniature receivers on human beings. Yet, it is the variety of civil application that improves the measurement accuracy of the originally military technology by an order (or several orders) of magnitude. This can be achieved either by exploiting secondary signals or by proposing innovative algorithms. The research of Adrian Wagli belongs to the latter category as it presents (with an excellent rigor) innovative algorithms and data processing approaches which turn signals from small GPS receivers and miniature but very imprecise Micro-electromechanical (MEMS)-IMU into a convincing measurement instrument capable of tracking the skier's 2-G turn with 0.01% accuracy. The amalgam of high precision and small instrumentation then allows tracing movement of athletes not once in a while, but continuously at 100 times per second. Thus, through the practically continuous measurements of 3D position, velocity and orientation, the sportsmen's performance parameters can be deduced. Using it in sports like alpine skiing is very challenging task due to the encountered dynamic and the mountain surroundings that block the reception of satellite signals. Therefore, if the technology finds its place in such relatively hostile conditions, it can be" surely used for other purposes in more benign environment. At the same time it represents a very motivating factor for the research undertaken at the country to which such sport belongs. In his work, Adrian Wagli demonstrates for the first time that redundant configuration of low-cost MEMS-IMUs allows determining orientation better than 1 degree RMS and that the autonomous positioning of decimeter accuracy is feasible with these sensors up to 30-second long outages of GPS signals even in high dynamic. Although the thesis is application-driven, i.e. the work results in. several algorithms and software modules applicable to real scenarios; it contains, at the same time, a I number of novel concepts applicable to other domains of navigation and kinematic positioning. The nicely presented combination of theory and practice will therefore satisfy a wide spectrum of readers. Note de contenu : 1 Introduction 1.1 Context 1.2 Particularities Related to Sport Applications 1.3 Objectives 1.4 Methodology 2 From Sports to Navigation 2.1 Criteria of Sport Applications 2.1.1 Accuracy Requirements 2.2 Methods for Trajectory Determination 2.2.1 Imagery 2.2.2 Satellite and Inertial Navigation 2.2.3 Alternative Techniques Based on Position Fixing 2.2.4 Complementary Methods to Trajectory Determination 2.2.5 Summary 2.3 Instrumentation for Satellite and Inertial Navigation 2.3.1 Overview on GNSS and Processing Methods 2.3.2 Inertial Measurement Units 2.3.3 Other Aspects Related to System Architecture 3 Measurements, Models and Estimation Methods 3.1 Inertial Measurement Model 3.1.1 Generalized Error Model for Inertial Observations 3.1.2 Simplified Error Model for Inertial Observations 3.2 Magnetic Measurements 3.3 GPS Observations 3.3.1 Code Measurements 3.3.2 Carrier-Phase Measurements 3.3.3 Carrier-Phase Smoothing 3.3.4 Doppler Measurements 3.3.5 Differential GPS 3.4 GPS/INS Sensor Fusion 3.4.1 Integration Constraints 3.4.2 Integration Strategy Trade-offs 3.4.3 Kalman Filtering 3.4.4 Optimal Smoothing 3.5 Implementation of GPS Processing 3.5.1 Definition of the State Vector 3.5.2 Initialization 3.5.3 State Propagation 3.5.4 Measurement Updates 3.6 Implementation of GPS/INS Integration 3.6.1 Definition of the State Vector 3.6.2 Initialization 3.6.3 Strapdown Inertial Navigation 3.6.4 Measurement Updates 4 GPS/MEMS-IMU System Performance 4.1 Experimental Setup 4.2 GPS/MEMS-IMU Performance 4.2.1 Satellite Navigation 4.2.2 GPS/MEMS-IMU Integration 4.2.3 GPS/MEMS-IMU Integration during Reduced Satellite Reception 4.2.4 Benefits of RTS Smoothing 4.3 Benefits of UKF 4.3.1 Navigation Performance 4.3.2 Implementation Aspects 4.4 Magnetic Sensors 4.5 Orientation Initialization 4.5.1 Evaluation based on Simulations 4.5.2 Experimental Evaluation 5 MEMS-IMU Error Modeling 5.1 Static Evaluation by Allan Variance 5.2 Static Estimation of the Noise Parameters 5.3 Dynamic Error Model Investigation 5.3.1 Estimation of the Relative Alignment of the MEMS-IMU 5.3.2 Estimation of the Reference Values for the Inertial Sensor Errors 5.3.3 Error Model Analysis 5.3.4 Relevance to Kalmari Filtering 5.4 Investigation of more Complex Error Models 6 Performance Improvement through Redundant IMUs 6.1 INS Redundancy Approaches in Inertial Navigation 6.2 Geometrical Arrangement of Redundant IMUs 6.3 Noise Reduction and Direct Noise Estimation 6.3.1 Noise Reduction 6.3.2 Direct Noise Estimation 6.4 Fault Detection and Isolation 6.5 System and Observation Model for the Redundant IMU Integration 6.5.1 Synthetic IMU Integration 6.5.2 Extended IMU Mechanization 6.5.3 Geometrically-Constrained Mechanization 6.6 Navigation Performance Improvement 6.6.1 Algorithm Selection 6.6.2 Assessment Based on Experiments 6.6.3 Assessment Based on Emulation 6.6.4 Notes on the Observability 6.6.5 Orientation Initialization and Inertial Error Estimation 7 From Navigation to Performance Assessment in Sport 7.1 Trajectory Modeling Approaches 7.1.1 Cubic Splines Smoothing 7.1.2 Additional Kalman Filtering 7.1.3 Limitations of Trajectory Modeling . 7.2 Trajectory Matching 7.2.1 Problem Definition 7.2.2 Extension of Cubic Spline Smoothing 7.2.3 Eigenvector Approach for Feature-Based Correspondence 7.2.4 Position Accuracy Improvement through Trajectory Matching 7.2.5 Risk Related to Trajectory Matching 7.3 Trajectory Comparison 7.3.1 Spatial Trajectory Comparison Approach 7.3.2 Methodology for Trajectory Comparison 7.3.3 Alternative Methods for Trajectory Comparison 7.3.4 Visualization Aspects 7.4 Position-Based Chronornetry 7.5 Orientation Related Assessment - Skiing 7.6 Orientation Related Assessment - Motorcycling 7.6.1 Reference Frame Aspects 7.6.2 Computation of the Lateral Slipping of Tires 7.6.3 Evaluation of the Tire Characteristics 7.6.4 Other Perspectives 8 Conclusions and Perspectives 8.1 Conclusions 8.2 Perspectives Numéro de notice : 15514 Affiliation des auteurs : non IGN Autre URL associée : URL EPFL Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.5075/epfl-thesis-4288 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-77.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62747

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
15514-01	30.83	Livre	Centre de documentation	Géodésie	Disponible

Topex-poseidon, Scientific results / American Geophysical Union (1996)

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GEOSAT, Sea level from space / American Geophysical Union (1991)

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Ocean tides and tectonic plate motions from LAGEOS / John M. Dow (1988)

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