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Auteur Tong Ning |
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Affiner la recherche Interroger des sources externesHomogenizing GPS integrated water vapor time series: Benchmarking break detection methods on synthetic data sets / Roeland Van Malderen in Earth and space science, vol 7 n° 5 (May 2020)
Titre : Homogenizing GPS integrated water vapor time series: Benchmarking break detection methods on synthetic data sets Type de document : Article/Communication Auteurs : Roeland Van Malderen, Auteur ; Eric Pottiaux, Auteur ; Anna Klos, Auteur ; P. Domonkos, Auteur ; Michal Elias, Auteur ; Tong Ning, Auteur ; Olivier Bock Année de publication : 2020 Projets : GNSS4SWEC / Article en page(s) : n° e2020EA001121 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] coordonnées GNSS
[Termes IGN] données hétérogènes
[Termes IGN] homogénéisation
[Termes IGN] jeu de données
[Termes IGN] prévision météorologique
[Termes IGN] série temporelle
[Termes IGN] station permanente
[Termes IGN] teneur intégrée en vapeur d'eauRésumé : (auteur) We assess the performance of different break detection methods on three sets of benchmark data sets, each consisting of 120 daily time series of integrated water vapor differences. These differences are generated from the Global Positioning System (GPS) measurements at 120 sites worldwide, and the numerical weather prediction reanalysis (ERA‐Interim) integrated water vapor output, which serves as the reference series here. The benchmark includes homogeneous and inhomogeneous sections with added nonclimatic shifts (breaks) in the latter. Three different variants of the benchmark time series are produced, with increasing complexity, by adding autoregressive noise of the first order to the white noise model and the periodic behavior and consecutively by adding gaps and allowing nonclimatic trends. The purpose of this “complex experiment” is to examine the performance of break detection methods in a more realistic case when the reference series are not homogeneous. We evaluate the performance of break detection methods with skill scores, centered root mean square errors (CRMSE), and trend differences relative to the trends of the homogeneous series. We found that most methods underestimate the number of breaks and have a significant number of false detections. Despite this, the degree of CRMSE reduction is significant (roughly between 40% and 80%) in the easy to moderate experiments, with the ratio of trend bias reduction is even exceeding the 90% of the raw data error. For the complex experiment, the improvement ranges between 15% and 35% with respect to the raw data, both in terms of RMSE and trend estimations. Numéro de notice : A2020-335 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2020EA001121 Date de publication en ligne : 20/04/2020 En ligne : https://doi.org/10.1029/2020EA001121 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96837
in Earth and space science > vol 7 n° 5 (May 2020) . - n° e2020EA001121[article]
Titre : Determination of the local tie vector between the VLBI and GNSS reference points at Onsala using GPS measurements Type de document : Article/Communication Auteurs : Tong Ning, Auteur ; Rüdiger Haas, Auteur ; Gunnar Elgered, Auteur Année de publication : 2015 Article en page(s) : pp 711 - 723 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] co-positionnement
[Termes IGN] données GPS
[Termes IGN] données ITGB
[Termes IGN] écart type
[Termes IGN] point de liaison (géodésie)
[Termes IGN] point géodésique
[Termes IGN] précision millimétrique
[Termes IGN] SuèdeRésumé : (auteur) Two gimbal-mounted GNSS antennas were installed on each side of the radome-enclosed 20 m VLBI radio telescope at the Onsala Space Observatory. GPS data with a 1 Hz sampling rate were recorded for five semi-kinematic and four kinematic observing campaigns. These GPS data were analysed together with data from the IGS station ONSA with an in-house Matlab-based GPS software package, using the double-difference analysis strategy. The coordinates of the GNSS antennas on the telescope were estimated for different observation angles of the telescope, at specific epochs, and used to calculate the geodetic reference point of the telescope. The local tie vector between the VLBI and the ONSA GNSS reference points in a geocentric reference frame was hence obtained. The two different types of observing campaigns gave consistent results of the estimated local tie vector and the axis offset of the telescope. The estimated local tie vector obtained from all nine campaigns gave standard deviations of 1.5, 1.0, and 2.9 mm for the geocentric X, Y, and Z components, respectively. The result of the estimated axis offset of the VLBI telescope shows a difference of 0.3 mm, with a standard deviation of 1.9 mm, with respect to a reference value obtained by two local surveys carried out in 2002 and 2008. Our results show that the presented method can be used as a complement to the more accurate but more labour intensive classical geodetic surveys to continuously monitor the local tie at co-location stations with an accuracy of a few millimetres Numéro de notice : A2015-355 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0809-1 Date de publication en ligne : 05/04/2015 En ligne : https://doi.org/10.1007/s00190-015-0809-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76778
in Journal of geodesy > vol 89 n° 7 (July 2015) . - pp 711 - 723[article]
Titre : GPS meteorology : with focus on climate applications Type de document : Thèse/HDR Auteurs : Tong Ning, Auteur Editeur : Göteborg [Suède] : Chalmers University of Technology Année de publication : 2012 Importance : 82 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-91-7385-675-1 Note générale : Thesis for the degree of doctor of philosophy, Department of Earth and Space Sciences, Chalmers University of Technology, Gothenburg, Sweden Langues : Anglais (eng) Descripteur : [Termes IGN] données GPS
[Termes IGN] modèle atmosphérique
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur en vapeur d'eau
[Termes IGN] teneur intégrée en vapeur d'eauRésumé : (auteur) The vital role of water vapour in the Earth’s climate system requires measurements of the atmospheric Integrated Water Vapour (IWV) with a long-term stability and a high accuracy. This work focuses on using the Global Positioning System (GPS) to provide IWV estimates for climate applications. The advantages of the GPS measurements are that they can be performed independently on the weather and have a high temporal resolution (a few minutes) as well as a continuously improving spatial resolution (a few km for some local networks). The uncertainty of the GPS-derived IWV highly depends on the accuracy of the estimated Zenith Total Delay (ZTD), which is determined by many parameters, i.e. satellite orbit errors, ionospheric delay, signal multipath, antenna related errors (e.g. phase centre variations), and mapping functions. We demonstrated that the uncertainty of the GPS-derived IWV below 1 kg/m2 is achievable. The long-term change of the IWV can be an independent data source to detect climate changes. Using a global GPS IWV data set covering a 15-year-long time period, we found estimated IWV trends in a range from ¡1.65 to +2.32 kg/(m2¢decade) which, however, are comparable to the trend uncertainties varying from 0.21 to 1.52 kg/(m2¢decade). The trend uncertainty is mainly caused by the short-term variations of the IWV which cannot be modelled accurately. The uncertainty is also due to the errors in IWV estimates, which are random and/or elevation-dependent systematic errors. A higher elevation cutoff angle used in the GPS data analysis (a 25± was revealed for the time period investigated and for the region of Fennoscandia) can be an advantage to reduce the impact of such systematic errors. The GPS-derived IWV can also be used for the evaluation of climate models. The IWV derived from the GPS measurements acquired at 99 European sites, each with a maximum time series of 14 years, were compared to the IWV simulated by a regional climate model. Overall, a monthly mean difference of »0.5 kg/m2 (model¡GPS) is obtained where a significant seasonal variation is seen in the difference. The model is too dry in the summer. Study of the diurnal cycle of the IWV using both the GPS data and the model simulation shows a good agreement for the phase while a smaller amplitude is seen in the results from the model. Note de contenu : 1 Introduction
1.1 The role of water vapour in the climate system
1.2 Measurements of the atmospheric water vapour
1.3 Thesis structure
2 Measurement Techniques
2.1 Radiosonde
2.2 Radio techniques .
2.3 Summery of Paper A
3 Uncertainty Analysis of the IWV from GPS
3.1 Statistical analysis
3.2 Theoretical analysis
3.3 Summary of Paper B
4 GPS Meteorology for Climate Applications
4.1 Detection of climate changes using GPS data
4.2 Summary of Paper C
4.3 Evaluation of climate models using GPS data
4.4 Summary of Paper D
5 ConclusionsNuméro de notice : 14899 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD : Earth and Space Sciences : Chalmers University of Technology, Sweden : 2012 DOI : sans En ligne : https://core.ac.uk/download/pdf/70594409.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76783 Documents numériques
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