Centre de documentation
scientifique

Tropospheric refractivity and zenith path delays from least-squares collocation of meteorological and GNSS data / Karina Wilgan in Journal of geodesy, vol 91 n° 2 (February 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 2 (February 2017) . - pp 117 - 134 Titre : Tropospheric refractivity and zenith path delays from least-squares collocation of meteorological and GNSS data Type de document : Article/Communication Auteurs : Karina Wilgan, Auteur ; Fabian Peter Hurter, Auteur ; Alain Geiger, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 117 - 134 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] collocation par moindres carrés [Termes IGN] données GNSS [Termes IGN] données météorologiques [Termes IGN] modèle atmosphérique [Termes IGN] prévision météorologique [Termes IGN] propagation troposphérique [Termes IGN] réfringence [Termes IGN] retard troposphérique zénithal Résumé : (Auteur) Precise positioning requires an accurate a priori troposphere model to enhance the solution quality. Several empirical models are available, but they may not properly characterize the state of troposphere, especially in severe weather conditions. Another possible solution is to use regional troposphere models based on real-time or near-real time measurements. In this study, we present the total refractivity and zenith total delay (ZTD) models based on a numerical weather prediction (NWP) model, Global Navigation Satellite System (GNSS) data and ground-based meteorological observations. We reconstruct the total refractivity profiles over the western part of Switzerland and the total refractivity profiles as well as ZTDs over Poland using the least-squares collocation software COMEDIE (Collocation of Meteorological Data for Interpretation and Estimation of Tropospheric Pathdelays) developed at ETH Zürich. In these two case studies, profiles of the total refractivity and ZTDs are calculated from different data sets. For Switzerland, the data set with the best agreement with the reference radiosonde (RS) measurements is the combination of ground-based meteorological observations and GNSS ZTDs. Introducing the horizontal gradients does not improve the vertical interpolation, and results in slightly larger biases and standard deviations. For Poland, the data set based on meteorological parameters from the NWP Weather Research and Forecasting (WRF) model and from a combination of the NWP model and GNSS ZTDs shows the best agreement with the reference RS data. In terms of ZTD, the combined NWP-GNSS observations and GNSS-only data set exhibit the best accuracy with an average bias (from all stations) of 3.7 mm and average standard deviations of 17.0 mm w.r.t. the reference GNSS stations. Numéro de notice : A2017-062 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0942-5 En ligne : http://dx.doi.org/10.1007/s00190-016-0942-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84275 [article]

GNSS meteorology in spatially dense networks / Fabian Peter Hurter (2014)  

Public Titre : GNSS meteorology in spatially dense networks Type de document : Thèse/HDR Auteurs : Fabian Peter Hurter, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2014 Collection : Astronomisch-Geodätische Arbeiten in der Schweiz, ISSN 0025-6676 num. 91 Importance : 185 Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-37-6 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Bernese [Termes IGN] données GNSS [Termes IGN] météorologie [Termes IGN] propagation du signal [Termes IGN] retard troposphérique zénithal [Termes IGN] signal GNSS [Termes IGN] station GNSS [Termes IGN] station météorologique [Termes IGN] teneur en vapeur d'eau [Termes IGN] traitement du signal Index. décimale : 30.84 Applications de géodésie spatiale à l'atmosphère Résumé : (auteur) Two basic products from GNSS meteorology have been investigated in detail: (a) the Zenith Total Delay (ZTD) and, (b) wet refractivity fields reconstructed from Zenith Wet Delays (ZWD).The thesis aims at quantifying the accuracies of GNSS-derived ZTDs and refractivities and at characterizing their temporal and spatial resolution. In a first study using operational radiosondes and Global Navigation Satellite System (GNSS) data from the Swiss meteorological station in Payerne, the following uncertainty figures are obtained: With respect to the radiosonde, the GNSS-derived ZTD has a 1–3mm dry bias. Annual systematic variations of the comparison are found to have an amplitude of 1–2 mm . Removal of most systematic effects from the GNSS minus radiosonde ZTD time series plus a thorough budget of the radiosonde uncertainties allows the derivation of the random GNSS uncertainties. In the winter half-year, the standard deviation is shown to be 2.5–3.5 mm , during the summer half-year we obtain 3.5–5.0 mm. In a further study in the western part of Switzerland, wet refractivities have been derived on the basis of interpolated ZWDs from the Automatic GNSS Network for Switzerland (AGNES). The employed interpolation algorithm is termed least-squares collocation. It makes use of a deterministic function to describe the general parametric field and a correlation function describing the spatial and temporal correlations between the zenith wet delays. Corresponding wet refractivities show accuracies superior to results from tomographic reconstructions of a similar data set. Further inclusion of ground meteorological measurements of temperature and water vapour pressure im- prove the derived refractivities in the lowest 2 km of the troposphere. Radio occultations are added to the reconstruction. The data combination enables the extension of the radio occultation profiles down to the ground. It is also shown that the GNSS data largely contributes to the profile quality above the atmospheric boundary layer. Transformation of the wet refractivities to humidity values with temperature profiles from a radiometer in Payerne show accuracies of a similar order of mag nitude to those from numerical weather prediction analysis. Hence, application of the algorithm in nowcasting of rain or investigating boundary layer processes are envisaged. The third part of the thesis investigates the results from a campaign network of 34 geodetic- grade receivers. They were deployed close to and around Zermatt (Switzerland) for one month in summer 2010. The stations were spaced at distances of a few kilometers from each other and at heights between 1600–3500 m above mean sea level. The mountainous region provides an excellent natural laboratory to investigate the influences affecting the accuracy of the ZTD. Additionally, the Alpine region is prone to small-scale fluctuations in the troposphere. Thus, the spatial and temporal variability of the ZTD has been investigated. The influences of satellite obstructions, antenna and receiver types and a number of processing strategies on the estimated ZTD are analysed and validated with measurements from radiosondes launched during the campaign. The analysis suggests that 1 hour temporal resolution should not be undercut for estimated ZTDs. A temporal resolution of 30 minutes introduces more noise without better following the tropospheric fluctuation. The horizontal variability observed in ZTDs indicates correlation scale lengths of a few kilometers. From comparison with radiosondes, the ZTD uncertainty is shown to have 4–6 mm standard deviation. Some stations show signs of systematic effects caused by multipath and low- quality antenna patterns. Through the GNSS-inherent negative correlation of height with zenith delay, both parameters are similarly affected by these systematic influences. The performance of the numerical weather prediction model COSMO-2 is characterized in terms of integrated atmospheric state. The analysis yields preliminary recommendations on the assimilation of zenith total path delays into weather models in regions of highly complex topography such as the Swiss Alps. Note de contenu : 1 Introduction 1.1 Review of GNSS meteorology 1.2 Potential synergies with other water vapour measurements . 1.3 Challenges in GNSS meteorology 1.4 Objectives and structure of the thesis 2 Theory 2.1 Refractivity and path delay in the atmosphere 2.2 Collocation with the software COMEDIE 2.3 Water vapour tomography software AWATOS2 3 Comparison of zenith path delays from GNSS and radiosonde measurements 3.1 Data description 3.2 Formal uncertainties of ZTD estimates from GNSS 3.3 Comparison of ZTDs 3.4 Influence of processing strategy on GNSS ZTDs 3.5 2nd and 3rd order ionospheric effects . 3.6 Comparison of ZWDs 3.7 Formal uncertainty of radiosonde-derived ZTDs 3.8 Derivation of random GNSS ZTD uncertainty 3.9 Correlation between GNSS heights and ZTDs 3.10 Discussion . 3.11 Conclusion . 4 Payerne profile study 4.1 Abstract 4.2 Introduction 4.3 Description of data sets 4.4 Processing 4.5 Results . 4.6 Discussion 4.7 Conclusions 5 Geodetic water vapor campaign in Zermatt 5.1 Data description and processing 5.2 Troposphere results 5.3 Conclusions 6 Conclusions Numéro de notice : 12952 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère En ligne : http://www.sgc.ethz.ch/sgc-volumes/sgk-91.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76823

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
12952-01	30.84	Livre	Centre de documentation	Géodésie	Disponible

4D GPS water vapor tomography: new parameterized approaches / Donat Perler in Journal of geodesy, vol 85 n° 8 (August 2011)  

Public [article]  inJournal of geodesy > vol 85 n° 8 (August 2011) . - pp 539 - 550 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] voxel Résumé : (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 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2011081	RAB	Revue	Centre de documentation	En réserve L003	Disponible