Catalogue en ligne IGN

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

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
15512-01	30.83	Livre	Centre de documentation	Géodésie	Disponible

IGN

Centre de documentation
scientifique

Accueil

Sélection de la langue

Adresse

Se connecter

Actualité

L'actu ! Horaires du CDOS

Informations pratiques

Exemplaires(1)

IGN / ENSG

L'IGN a pour vocation

Accès directs

2014 -2024 IGN

IGN

Centre de documentationscientifique

Accueil

Sélection de la langue

Adresse

Se connecter

Actualité

L'actu ! Horaires du CDOS

Informations pratiques

Exemplaires(1)

IGN / ENSG

L'IGN a pour vocation

Accès directs

2014 -2024 IGN

Centre de documentation
scientifique