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4D GPS water vapor tomography: new parameterized approaches / Donat Perler in Journal of geodesy, vol 85 n° 8 (August 2011)
[article]
Titre : 4D GPS water vapor tomography: new parameterized approaches Type de document : Article/Communication Auteurs : Donat Perler, Auteur ; Alain Geiger, Auteur ; Fabian Peter Hurter, Auteur Année de publication : 2011 Article en page(s) : pp 539 - 550 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Alpes
[Termes IGN] coordonnées ellipsoïdales
[Termes IGN] distribution spatiale
[Termes IGN] données GPS
[Termes IGN] données météorologiques
[Termes IGN] filtre de Kalman
[Termes IGN] prédiction
[Termes IGN] réfraction atmosphérique
[Termes IGN] réfringence
[Termes IGN] signal GPS
[Termes IGN] Suisse
[Termes IGN] tomographie
[Termes IGN] troposphère
[Termes IGN] vapeur d'eau
[Termes IGN] voxelRésumé : (Auteur) Water vapor is a key variable in numerical weather prediction, as it plays an important role in atmospheric processes. Nonetheless, the distribution of water vapor in the atmosphere is observed with a coarse resolution in time and space compared to the resolution of numerical weather models. GPS water vapor tomography is one of the promising methods to improve the resolution of water vapor measurements. This paper presents new parameterized approaches for the determination of water vapor distribution in the troposphere by GPS. We present the methods and give first results validating the approaches. The parameterization of voxels (volumetric pixels) by trilinear and spline functions in ellipsoidal coordinates are introduced in this study. The evolution in time of the refractivity field is modeled by a Kalman filter with a temporal resolution of 30s, which corresponds to the available GPS-data rate. The algorithms are tested with simulated and with real data from more than 40 permanent GPS receiver stations in Switzerland and adjoining regions covering alpine areas. The investigations show the potential of the new parameterized approaches to yield superior results compared to the non parametric classical one. The accuracy of the tomographic result is quantified by the inter-quartile range (IQR), which is decreased by 10–20% with the new approaches. Further, parameterized voxel solutions have a substantially smaller maximal error than the non parameterized ones. Simulations show a limited ability to resolve vertical structures above the top station of the network with GPS tomography. Numéro de notice : A2011-359 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0454-2 Date de publication en ligne : 08/03/2011 En ligne : https://doi.org/10.1007/s00190-011-0454-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31138
in Journal of geodesy > vol 85 n° 8 (August 2011) . - pp 539 - 550[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-2011081 RAB Revue Centre de documentation En réserve L003 Disponible Ionospheric response to the geomagnetic storm on august 21, 2003 over China using GNSS-based tomographic technique / D. Wen in IEEE Transactions on geoscience and remote sensing, vol 48 n° 8 (August 2010)
[article]
Titre : Ionospheric response to the geomagnetic storm on august 21, 2003 over China using GNSS-based tomographic technique Type de document : Article/Communication Auteurs : D. Wen, Auteur ; Y. Yuan, Auteur ; J. Ou, Auteur ; K. Zhang, Auteur Année de publication : 2010 Article en page(s) : pp 3212 - 3217 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Chine
[Termes IGN] ionosphère
[Termes IGN] perturbation ionosphérique
[Termes IGN] positionnement par GNSS
[Termes IGN] tempête magnétique
[Termes IGN] tomographieRésumé : (Auteur) The impacts of the August 21, 2003 geomagnetic storm on the ionosphere over China have been first investigated by using the so-called computerized ionospheric tomography (CIT) technique and the observations of the Crustal Movement Observation Network of China. Tomographic results show that the main ionospheric effects of this geomagnetic storm over China are as follows: (1) the negative storm phase effect appears in the F region and (2) the positive storm phase effect occurs above the F region. Meanwhile, some key features in the ionospheric structure have been revealed in the ionospheric images during the storm; this includes the disturbances and an elongated region of the reduced electron density at the latitude around 32°N. Statistical comparisons are carried out to confirm the reliability of the global-navigation-satellite-system-based CIT reconstruction results using the profile obtained from ionosonde observations. Numéro de notice : A2010-309 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2010.2044579 En ligne : https://doi.org/10.1109/TGRS.2010.2044579 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30503
in IEEE Transactions on geoscience and remote sensing > vol 48 n° 8 (August 2010) . - pp 3212 - 3217[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 065-2010081 RAB Revue Centre de documentation En réserve L003 Disponible Better weather prediction using GPS: water vapor tomography in the Swiss Alps / Simon Lutz in GPS world, vol 21 n° 7 (July 2010)
[article]
Titre : Better weather prediction using GPS: water vapor tomography in the Swiss Alps Type de document : Article/Communication Auteurs : Simon Lutz, Auteur ; Donat Perler, Auteur ; Marc Troller, Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : pp 40 - 47 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] affaiblissement de la précision
[Termes IGN] Alpes centrales
[Termes IGN] atténuation du signal
[Termes IGN] humidité de l'air
[Termes IGN] prévision météorologique
[Termes IGN] Suisse
[Termes IGN] teneur en vapeur d'eau
[Termes IGN] tomographie
[Termes IGN] traitement du signalRésumé : (Editeur) [...] Forecasting ability has improved as measurement technology, communications, and the understanding of atmospheric processes have improved. Meteorologists use measure- ments from various types of sensors and mathematical models to predict its future state. Yet better sampling of the current state of the atmosphere, particularly water vapor, is needed to produce more accurate and more timely forecasts. GPS can help. The signals from the GPS satellites must transit the atmosphere on their way to a receiver on the Earth's surface. The atmosphere's atoms and molecules slow down the signals so that they arrive slightly later than they would if the Earth was surrounded by a vacuum, and this effect shows up in the GPS receiver measurements. The receiver or measurement processing software needs to remove or model the effect to obtain accurate receiver positions. On the other hand, if all parameters affecting GPS measurements such as satellite and receiver coordinates are well known, then the delay imparted by the atmosphere can be estimated. It is possible to separate the effect of water vapor from that of the dry gases such as nitrogen, oxygen, and carbon dioxide and to provide a measure of the atmosphere's moisture content. Several national weather agencies are ingesting such estimates from networks of GPS receivers into experimental or operational numerical weather forecast models. But these values represent an integrated measure of moisture above a receiver. Profiles of how moisture is distributed with height would be more useful and might lead to better weather forecasts. In this month's column, a team of Swiss researchers discuss how they use data from a network of GPS receivers and the technique of tomography to obtain such profiles. Numéro de notice : A2010-271 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30465
in GPS world > vol 21 n° 7 (July 2010) . - pp 40 - 47[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 067-2010071 RAB Revue Centre de documentation En réserve L003 Disponible Measuring wood density by means of X-ray computer tomography / Charline Freyburger in Annals of Forest Science, Vol 66 n° 8 (December 2009)
[article]
Titre : Measuring wood density by means of X-ray computer tomography Titre original : Mesure de la densité du bois par tomographie à rayons X Type de document : Article/Communication Auteurs : Charline Freyburger, Auteur ; Fleur Longuetaud, Auteur ; Frédéric Mothe, Auteur ; Thiéry Constant, Auteur ; Jean-Michel Leban , Auteur Année de publication : 2009 Article en page(s) : n° 804 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] biomasse
[Termes IGN] densité du bois
[Termes IGN] étalonnage d'instrument
[Termes IGN] puits de carbone
[Termes IGN] rayon X
[Termes IGN] tomographieRésumé : (Auteur) Wood density is a characteristic of major interest. Usually, it is used as an indicator of wood quality; however, in the context of global change, it is increasingly used for biomass and carbon storage estimations. X-ray computer tomography is a method which enables quick estimates of wood density after applying a calibration procedure.
A review of the literature is presented in this article. Most of the previous studies have been performed in the 80’s or at the beginning of the 90’s. In this study, the relationship between wood density and Hounsfield numbers was investigated using a recent medical scanner. A linear relationship was fitted using a calibration data set which consisted in tropical wood samples representing a large range of densities ranging between 133 and 1319 kg m−3, and then validated using an independent data set (mainly temperate tree species). The fitted relationships were very strong (R2 > 0.999), whichever the tested scanner settings, with slight but significant effects of the current voltage and reconstruction filters. The RMSE values computed from the validation data set ranged between 5.4 and 7.7 kg m−3 for densities ranging between 364 and 821 kg m−3. In conclusion, this method of calibration enables the use of a medical scanner to obtain maps of wood density, in a fast and non destructive way, and with a very good accuracy. Very interesting perspectives are opened regarding biomass distribution within trees.Numéro de notice : A2009-610 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1051/forest/2009071 Date de publication en ligne : 25/11/2009 En ligne : https://www.afs-journal.org/articles/forest/full_html/2009/08/f09029/f09029.html Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=72893
in Annals of Forest Science > Vol 66 n° 8 (December 2009) . - n° 804[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité IFN-001-P000694 PER Revue Nogent-sur-Vernisson Salle périodiques Exclu du prêt
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 thesisLangues : 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] voxelIndex. 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 ConclusionsNuméro 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 Réservation
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