Descripteur
Termes IGN > sciences naturelles > physique > optique > optique physique > radiométrie > rayonnement électromagnétique > propagation troposphérique > retard troposphérique > retard troposphérique zénithal
retard troposphérique zénithal |
Documents disponibles dans cette catégorie (72)
Ajouter le résultat dans votre panier
Visionner les documents numériques
Affiner la recherche Interroger des sources externes
Etendre la recherche sur niveau(x) vers le bas
Integrated water vapour observations in the Caribbean arc from a network of ground-based GNSS receivers during EUREC4A / Olivier Bock in Earth System Science Data, vol 13 n° 5 (May 2021)
[article]
Titre : Integrated water vapour observations in the Caribbean arc from a network of ground-based GNSS receivers during EUREC4A Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Pierre Bosser , Auteur ; Cyrille Flamant, Auteur ; Erik Doerflinger, Auteur ; Friedhelm Jansen, Auteur ; Romain Fagès , Auteur ; Sandrine Bony, Auteur ; Sabrina Schnitt, Auteur Année de publication : 2021 Projets : VEGAN / Bock, Olivier, EUREC4A / Bock, Olivier Article en page(s) : pp 2407 - 2436 Note générale : bibliographie
This work was supported by the CNRS program LEFE/INSU through the project VEGAN. The EUREC4A project was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 694768).Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Caraïbes
[Termes IGN] données auxiliaires
[Termes IGN] données GNSS
[Termes IGN] données météorologiques
[Termes IGN] erreur systématique
[Termes IGN] humidité de l'air
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur intégrée en vapeur d'eauRésumé : (auteur) Ground-based Global Navigation Satellite System (GNSS) measurements from nearly fifty stations distributed over the Caribbean Arc have been analysed for the period 1 January–29 February 2020 in the framework of the EUREC4A (Elucidate the Couplings Between Clouds, Convection and Circulation) field campaign. The aim of this effort is to deliver high-quality Integrated Water Vapour (IWV) estimates to investigate the moisture environment of mesoscale cloud patterns in the Tradewinds and their feedback on the large-scale circulation and energy budget. This paper describes the GNSS data processing procedures and assesses the quality of the GNSS IWV retrievals from four operational streams and one reprocessed research stream which is the main data set used for offline scientific applications. The uncertainties associated with each of the data sets, including the zenith tropospheric delay (ZTD) to IWV conversion methods and auxiliary data, are quantified and discussed. The IWV estimates from the reprocessed data set are compared to the Vaisala RS41 radiosonde measurements operated from the Barbados Cloud Observatory (BCO) and to the measurements from the operational radiosonde station at Grantley Adams international airport (GAIA). A significant dry bias is found in the GAIA humidity observations with respect to the BCO sondes (−2.9 kg m−2) and the GNSS results (−1.2 kg m−2). A systematic bias between the BCO sondes and GNSS is also observed (1.7 kg m−2) where the Vaisala RS41 measurements are moister than the GNSS retrievals. The IWV estimates from a colocated microwave radiometer agree with the BCO soundings after an instrumental update on 27 January, while they exhibit a dry bias compared to the soundings and to GNSS before that date. IWV estimates from the ECMWF fifth generation reanalysis (ERA5) are overall close to the GAIA observations, probably due to the assimilation of these observations in the reanalysis. However, during several events where strong peaks in IWV occurred, ERA5 is shown to significantly underestimate the GNSS derived IWV peaks. Two successive peaks are observed on 22 January and 23/24 January which were associated with heavy rain and deep moist layers extending from the surface up to altitudes of 3.5 and 5 km, respectively. ERA5 significantly underestimates the moisture content in the upper part of these layers. The origins of the various moisture biases are currently being investigated. We classified the cloud organisation for five representative GNSS stations across the Caribbean Arc and found that the environment of Fish cloud patterns to be moister than that of Flowers cloud patterns which, in turn, is moister than the environment of Gravel cloud patterns. The differences in the IWV means between Fish and Gravel were assessed to be significant. Finally, the Gravel moisture environment was found to be similar to that of clear, cloud-free conditions. The moisture environment associated with the Sugar cloud pattern has not been assessed because it was hardly observed during the first two months of 2020. The reprocessed ZTD and IWV data set from 49 GNSS stations used in this study are available from the AERIS data center (https://doi.org/10.25326/79; Bock (2020b)). Numéro de notice : A2021-172 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/essd-13-2407-2021 Date de publication en ligne : 24/02/2021 En ligne : http://dx.doi.org/10.5194/essd-13-2407-2021 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97213
in Earth System Science Data > vol 13 n° 5 (May 2021) . - pp 2407 - 2436[article]IWV retrieval from ground GNSS receivers during NAWDEX / Pierre Bosser in Advances in geosciences, vol 55 ([01/02/2021])
[article]
Titre : IWV retrieval from ground GNSS receivers during NAWDEX Type de document : Article/Communication Auteurs : Pierre Bosser , Auteur ; Olivier Bock , Auteur Année de publication : 2021 Projets : DIP-NAWDEX / Rivière, Gwendal Article en page(s) : pp 13 - 22 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Atlantique Nord
[Termes IGN] données GNSS
[Termes IGN] données météorologiques
[Termes IGN] erreur systématique
[Termes IGN] GIPSY-OASIS
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur intégrée en vapeur d'eauRésumé : (auteur) A ground-based network of more than 1200 Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) was analysed using GIPSY-OASIS II software package for the documentation of time and space variations of water vapor in atmosphere during the North Atlantic Waveguide and Downstream impact EXperiment (NAWDEX) during fall 2016. The network extends throughout the North Atlantic, from the Caribbeans to Morocco through Greenland. This paper presents the methodology used for GNSS data processing, screening, and conversion of Zenith Tropospheric Delay (ZTD) estimates to Integrated Water Vapor content (IWV) using surface parameters from reanalysis. The retrieved IWV are used to evaluate the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses ERAI and ERA5. ERA5 shows an overall improvement over ERAI in representing the spatial and temporal variability of IWV over the study area. The mean bias is decreased from 0.31±0.63 to 0.19±0.56 kg m−2 (mean ±1σ over all stations) and the standard deviation reduced from 2.17±0.67 to 1.64±0.53 kg m−2 combined with a slight improvement in correlation coefficient from 0.95 to 0.97. At regional scale, both reanalyses show a general wet bias at mid and northern latitudes but a dry bias in the Caribbeans. We hypothesize this results from the different nature of data being assimilated over the tropical oceans. This GNSS IWV data set is intended to be used for a better description of the high impact weather events that occurred during the NAWDEX experiment. Numéro de notice : A2021-174 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/adgeo-55-13-2021 Date de publication en ligne : 01/02/2021 En ligne : https://doi.org/10.5194/adgeo-55-13-2021 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97223
in Advances in geosciences > vol 55 [01/02/2021] . - pp 13 - 22[article]Copula-based modeling of dependence structure in geodesy and GNSS applications: case study for zenith tropospheric delay in complex terrain / Roya Mousavian in GPS solutions, vol 25 n° 1 (January 2021)
[article]
Titre : Copula-based modeling of dependence structure in geodesy and GNSS applications: case study for zenith tropospheric delay in complex terrain Type de document : Article/Communication Auteurs : Roya Mousavian, Auteur ; Christof Lorenz, Auteur ; Masoud Mashhadi Hossainali, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 12 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] corrélation croisée normalisée
[Termes IGN] dissymétrie
[Termes IGN] données GNSS
[Termes IGN] Europe centrale
[Termes IGN] modèle atmosphérique
[Termes IGN] prévision météorologique
[Termes IGN] retard troposphérique zénithal
[Termes IGN] série temporelleRésumé : (auteur) Modeling and understanding the statistical relationships between geophysical quantities is a crucial prerequisite for many geodetic applications. While these relationships can depend on multiple variables and their interactions, commonly used scalar methods like the (cross) correlation are only able to describe linear dependencies. However, particularly in regions with complex terrain, the statistical relationships between variables can be highly nonlinear and spatially heterogeneous. Therefore, we introduce Copula-based approaches for modeling and analyzing the full dependence structure. We give an introduction to Copula theory, including five of the most widely used models, namely the Frank, Clayton, Ali-Mikhail-Haq, Gumbel and Gaussian Copula, and use this approach for analyzing zenith tropospheric delays (ZTDs). We apply modeled ZTDs from the Weather and Research Forecasting (WRF) model and estimated ZTDs through the processing of Global Navigation Satellite System (GNSS) data and evaluate the pixel-wise dependence structures of ZTDs over a study area with complex terrain in Central Europe. The results show asymmetry and nonlinearity in the statistical relationships, which justifies the application of Copula-based approaches compared to, e.g., scalar measures. We apply a Copula-based correction for generating GNSS-like ZTDs from purely WRF-derived estimates. Particularly the corrected time series in the alpine regions show improved Nash–Sutcliffe efficiency values when compared against GNSS-based ZTDs. The proposed approach is therefore highly suitable for analyzing statistical relationships and correcting model-based quantities, especially in complex terrain, and when the statistical relationships of the analyzed variables are unknown. Numéro de notice : A2021-007 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01044-4 Date de publication en ligne : 02/11/2020 En ligne : https://doi.org/10.1007/s10291-020-01044-4 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96297
in GPS solutions > vol 25 n° 1 (January 2021) . - n° 12[article]Improving smartphone-based GNSS positioning using state space augmentation techniques / Francesco Darugna (2021)
Titre : Improving smartphone-based GNSS positioning using state space augmentation techniques Type de document : Thèse/HDR Auteurs : Francesco Darugna, Auteur ; Steffen Schön, Directeur de thèse Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2021 Collection : DGK - C, ISSN 0065-5325 num. 864 Importance : 189 p. Note générale : bibliographie
Diese Arbeit ist gleichzeitig veröffentlicht in:Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Universität Hannover - ISSN 0174-1454, Nr. 368, Hannover 2021Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] antenne GNSS
[Termes IGN] étalonnage d'instrument
[Termes IGN] positionnement par GNSS
[Termes IGN] retard troposphérique zénithal
[Termes IGN] téléphone intelligentRésumé : (auteur) Low-cost receivers providing Global Navigation Satellite System (GNSS) pseudorange and carrier phase raw measurements for multiple frequencies and multiple GNSS constellations have become available on the market in the last years. This significantly has increased the number of devices equipped with the necessary sensors to perform precise GNSS positioning. GNSS pseudorange and carrier phase are used to compute user positions. While both observations are affected by different error sources, e.g. the passage through the atmosphere, only the carrier-phase has an ambiguous nature. The resolution of this ambiguity is a crucial factor to reach fast and highly precise GNSS-based positioning. Currently, several smartphones are equipped with a dual-frequency, multi-constellation receiver. The access to Android-based GNSS raw measurements has become a strong motivation to investigate the feasibility of smartphone-based high-accuracy positioning. The quality of smartphone GNSS measurements has been analyzed, suggesting that they often suffer from low signal-to-noise, inhomogeneous antenna gain and high levels of multipath. This workshows how to tackle several of the currently present obstacles and demonstrates centimeter-level positioning with a low-cost GNSS antenna and a low-cost GNSS receiver built into an off-the-shelf smartphone. Since the beginning of the research in smartphone-based positioning, the device’s GNSS antenna has been recognized as one of the main limitations. Besides Multipath (MP), the antenna radiation pattern is the main site-dependent error source of GNSS observations. An absolute antenna calibration has been performed for the dual-frequency smartphone HuaweiMate20X. Antenna Phase Center Offset (PCO), and Variations (PCV ) have been estimated to correct for the antenna impact on the L1 and L5 phase observations. Accordingly, the relevance of considering the individual PCO and PCV for the two frequencies is shown. The PCV patterns indicate absolute values up to 2 cm and 4 cm for L1 and L5, respectively. The impactof antenna corrections has been assessed in different multipath environments using a high-accuracy positioning algorithm employing an uncombined observation model and applying Ambiguity Resolution (AR). Experiments both in zero-baseline and short-baseline configurations have been performed. Instantaneous AR in the zero-baseline setup has been demonstrated, showing the potential for cm-level positioning with low-cost sensors available inside smartphones. In short-baselines configurations, no reliable AR is achieved without antenna corrections. However, after correcting for PCV, successful AR is demonstrated for a smartphone placed in a low multipath environment on the ground of a soccer field. For a rooftop open-skytest case with large multipath, AR was successful in 19 out of 35 data-sets. Overall, the antenna calibration is demonstrated being an asset for smartphone-based positioning with AR,showing cm-level 2D Root Mean Square Error (RMSE). In GNSS-based positioning, a user within a region covered by a network of reference stations can take advantage of the network-estimated augmentation parameters. Among the GNSS error sources, atmospheric delays have a strong impact on the positioning performance and the ability to resolve ambiguities. State Space Representation (SSR) atmospheric corrections, i.e. tropospheric and ionospheric delays, are commonly estimated for the approximate user position by interpolation from values calculated for the reference stations. Widely used interpolation techniques are Inverse Distance Weighted (IDW), Ordinary Kriging (OK)and Weighted Least Squares (WLS). The interpolation quality of such techniques during severe weather events and Traveling Ionospheric Disturbances (TIDs) is analyzed. To improve the interpolation performance during such events, modified WLS methods taking advantage of the physical atmospheric behavior are proposed. To support this interpolation approach, external information from Numerical Weather Models (NWM) for tropospheric interpolation and from TID modeling for ionospheric interpolation is introduced to the algorithms. The interpolation is assessed using simulated data (considering artificial and real network geometries), and real SSR parameters generated by network computation of GNSS measurements. As examples, two severe weather events in northern Europe in 2017 and one TID eventover Japan in 2019 have been analyzed. The interpolation of SSR Zenith Tropospheric Delay(ZTD) and ionospheric parameters is evaluated. Considering the reference station positions as rover locations, the modified WLS approach marks a lower RMSE in up to 80% of the cases during sharp weather fluctuations. Also, the average error can be decreased in 64% of the cases during the TID event investigated. Improvements up to factors larger than two are observed. Furthermore, specific cases are isolated, showing particular ZTD variations where significant errors (e.g. larger than 1 cm) can be reduced by up to 20% of the total amount. As a final product of the analysis, tropospheric and ionospheric messages are proposed. The messages contain the information needed to implement the suggested interpolation. Along with the need for accurate atmospheric models, the concept of consistency in the SSR corrections is crucial. A format that can transport all the SSR corrections estimated by a network is the Geo++ SSR format (SSRZ). Exploiting the features of the SSRZ format, the impact of an error in the transported ionospheric parameters is investigated. It is shown that the position estimation strongly depends on the ionospheric modeling and mismodeling can result in cm level errors, especially in the height component. Numéro de notice : 17182 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : Thesis : Geodäsie und Geoinformatik : Hanovre : 2021 En ligne : https://dgk.badw.de/fileadmin/user_upload/Files/DGK/docs/c-864.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98000 Estimation of tropospheric wet refractivity using tomography method and artificial neural networks in Iranian case study / Mir Reza Ghaffari Razin in GPS solutions, Vol 24 n° 3 (July 2020)
[article]
Titre : Estimation of tropospheric wet refractivity using tomography method and artificial neural networks in Iranian case study Type de document : Article/Communication Auteurs : Mir Reza Ghaffari Razin, Auteur ; Behzad Voosoghi, Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] coefficient de corrélation
[Termes IGN] données GPS
[Termes IGN] erreur moyenne quadratique
[Termes IGN] erreur relative
[Termes IGN] Iran
[Termes IGN] réfraction atmosphérique
[Termes IGN] réseau neuronal artificiel
[Termes IGN] retard troposphérique
[Termes IGN] retard troposphérique zénithal
[Termes IGN] tomographie par GPS
[Termes IGN] vapeur d'eau
[Termes IGN] voxelRésumé : (auteur) Using the observations from local and regional GPS networks, the estimation of slant wet delays (SWDs) is possible for each line of sight between satellite and receiver. The observations of SWD are used to model horizontal and vertical variations of the wet refractivity in the atmosphere above the study area. This work is done using the tomography method. In tomography, the horizontal variations of tropospheric wet refractivity are modeled with the polynomial in degree and rank of 2 with latitude and longitude as variables. Also, altitude variations are modeled in the form of discrete layers with constant heights. The main innovation is to estimate the tropospheric parameters for each line of sight by the artificial neural networks (ANNs). The SWD obtained from GPS observations for the different signals at each station is compared with the SWD generated by the ANNs (SWDGPS–SWDANNs). The square of the difference between these two values is introduced as the cost function in the ANNs. To evaluate, we used observations from October 27 to 31, 2011. The availability of GPS and radiosonde data is the main reason for choosing this timeframe. The correlation coefficient, root mean square error (RMSE), and relative error allow for evaluation of the proposed model. The results were also compared with the results of the voxel-based troposphere tomography method. For a more detailed evaluation, four test stations are selected and ANN zenith wet delays (ZWDANN) are compared with the ZWDGPS. Observations of test stations are not used in the modeling step. The correlation coefficient in the testing step for TomoANN and Tomovoxel is 0.9006 and 0.8863, respectively. The mean RMSE at 5 days for TomoANN and Tomovoxel is calculated as 0.63 and 0.71 mm/km, respectively. Also, the average relative error at the four test stations for TomoANN is 15.37% and for Tomovoxel it is 19.69%. The results demonstrate the better capability of the proposed method in the modeling of the tropospheric wet refractivity in the region of Iran. Numéro de notice : A2020-238 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-00979-y Date de publication en ligne : 10/04/2020 En ligne : https://doi.org/10.1007/s10291-020-00979-y Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94986
in GPS solutions > Vol 24 n° 3 (July 2020)[article]Performance of real-time undifferenced precise positioning assisted by remote IGS multi-GNSS stations / Zhiqiang Liu in GPS solutions, vol 24 n° 2 (April 2020)PermalinkThe impact of second-order ionospheric delays on the ZWD estimation with GPS and BDS measurements / Shaocheng Zhang in GPS solutions, vol 24 n° 2 (April 2020)PermalinkCombinatorial optimization applied to VLBI scheduling / A. Corbin in Journal of geodesy, vol 94 n°2 (February 2020)PermalinkAdvanced GNSS tropospheric products for monitoring severe weather events and climate, ch. 5. Use of GNSS Tropospheric Products for Climate Monitoring (Working Group 3) / Olivier Bock (2020)PermalinkConsistency and representativeness of integrated water vapour from ground-based GPS observations and ERA-Interim reanalysis / Olivier Bock in Atmospheric chemistry and physics, vol 19 n° 14 (July 2019)PermalinkParallel computation of regional CORS network corrections based on ionospheric-free PPP / Linyang Li in GPS solutions, vol 23 n° 3 (July 2019)PermalinkSensitivity of GPS tropospheric estimates to mesoscale convective systems in West Africa / Samuel Nahmani in Atmospheric chemistry and physics, vol 19 n° 14 (July 2019)PermalinkHigh-resolution models of tropospheric delays and refractivity based on GNSS and numerical weather prediction data for alpine regions in Switzerland / Karina Wilgan in Journal of geodesy, vol 93 n°6 (June 2019)PermalinkThe impact of relative and absolute GNSS positioning strategies on estimated coordinates and ZWD in the framework of meteorological applications / Alessandro Fermi in Applied geomatics, vol 11 n° 1 (March 2019)PermalinkA new global grid model for the determination of atmospheric weighted mean temperature in GPS precipitable water vapor / Liangke Huang in Journal of geodesy, vol 93 n° 2 (February 2019)Permalink