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Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates / Tobias Nilsson in Journal of geodesy, vol 91 n° 7 (July 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 7 (July 2017) . - pp 857 - 866 Titre : Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates Type de document : Article/Communication Auteurs : Tobias Nilsson, Auteur ; Benedikt Soja, Auteur ; Kyriakos Balidakis, Auteur ; Maria Karbon, Auteur ; Robert Heinkelmann, Auteur ; Zhiguo Deng, Auteur ; Harald Schuh, Auteur Année de publication : 2017 Article en page(s) : pp 857 - 866 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] analyse de données [Termes descripteurs IGN] filtre de Kalman [Termes descripteurs IGN] gradient de troposphère [Termes descripteurs IGN] interférométrie à très grande base [Termes descripteurs IGN] longueur du jour [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] retard troposphérique zénithal [Termes descripteurs IGN] temps universel Résumé : (Auteur) The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external information on the zenith wet delays (ZWD) and tropospheric gradients from GPS or numerical weather prediction models is studied. Additionally, we test estimating tropospheric gradients in the data analysis, which is normally not done. To evaluate the results, we compared the UT1-UTC values from the Intensives to those from simultaneous 24-h VLBI session. Furthermore, we calculated length of day (LOD) estimates using the UT1-UTC values from consecutive Intensives and compared these to the LOD estimated by GPS. We find that there is not much benefit in using external ZWD; however, including external information on the gradients improves the agreement with the reference data. If gradients are estimated in the data analysis, and appropriate constraints are applied, the WRMS difference w.r.t. UT1-UTC from 24-h sessions is reduced by 5% and the WRMS difference w.r.t. the LOD from GPS by up to 12%. The best agreement between Intensives and the reference time series is obtained when using both external gradients from GPS and additionally estimating gradients in the data analysis. Numéro de notice : A2017-298 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://doi.org/10.1007/s00190-016-0985-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85333 [article]

Robust GPS/BDS/INS tightly coupled integration with atmospheric constraints for long-range kinematic positioning / Houzeng Han in GPS solutions, vol 21 n° 3 (July 2017)  

Public [article]  inGPS solutions > vol 21 n° 3 (July 2017) . - pp 1285 – 1299 Titre : Robust GPS/BDS/INS tightly coupled integration with atmospheric constraints for long-range kinematic positioning Type de document : Article/Communication Auteurs : Houzeng Han, Auteur ; Jian Wang, Auteur Année de publication : 2017 Article en page(s) : pp 1285 – 1299 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] BDS-INS [Termes descripteurs IGN] GPS-INS [Termes descripteurs IGN] incertitude de position [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] positionnement cinématique [Termes descripteurs IGN] positionnement inertiel [Termes descripteurs IGN] résolution d'ambiguïté [Termes descripteurs IGN] signal BeiDou [Termes descripteurs IGN] signal GNSS [Termes descripteurs IGN] système à couplage étroit Résumé : (auteur) The combination of new global navigation satellite system (GNSS) has brought great benefits to reliable positioning and ambiguity resolution (AR), especially in restricted environments. However, kinematic positioning over long ranges is still a challenge due to the presence of significant atmospheric uncertainties, which contaminates the AR process. We present a tightly coupled strategy to integrate GNSS and inertial navigation system (INS) by adding ionospheric and tropospheric delay parameters and extending the stepwise AR by applying the partial ambiguity resolution (PAR) strategy. With the aid of INS predictions, the instantaneous AR can be achieved with the proposed atmospheric prediction model, along with a dual-frequency constraint ambiguity validation test. To remove the faults in both dynamic model and measurement model, a robust innovation filtering algorithm is proposed. A field vehicular test was conducted to validate the positioning performance of the proposed algorithm over long ranges. The results show that a reliable positioning solution is obtainable for the global positioning system (GPS)/BeiDou navigation satellite system (BDS)/INS integration system with baseline larger than 130 km. The average number of fixable ambiguities reaches 14.43 by applying PAR. In addition, the fixing ratio of having fixed more than three ambiguities reaches 98.57%. The results also indicate that the robust innovation filtering can efficiently detect the discrepancies in the filter. Numéro de notice : A2017-446 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0612-y En ligne : https://doi.org/10.1007/s10291-017-0612-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86367 [article]

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 descripteurs IGN] collocation par moindres carrés [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] données météorologiques [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] prévision météorologique [Termes descripteurs IGN] propagation troposphérique [Termes descripteurs IGN] réfringence [Termes descripteurs 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 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern 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]

Quantitative assessment of meteorological and tropospheric Zenith Hydrostatic Delay models / Di Zhang in Advances in space research, vol 58 n° 6 (September 2016)  

Public [article]  inAdvances in space research > vol 58 n° 6 (September 2016) . - pp 1033 - 1043 Titre : Quantitative assessment of meteorological and tropospheric Zenith Hydrostatic Delay models Type de document : Article/Communication Auteurs : Di Zhang, Auteur ; Jiming Guo, Auteur ; Ming Chen, Auteur ; Junbo Shi, Auteur ; Lv Zhou, Auteur Année de publication : 2016 Article en page(s) : pp 1033 - 1043 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes descripteurs IGN] analyse comparative [Termes descripteurs IGN] erreur systématique [Termes descripteurs IGN] évaluation [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] modèle numérique [Termes descripteurs IGN] radiosondage [Termes descripteurs IGN] retard troposphérique [Termes descripteurs IGN] retard troposphérique zénithal [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Tropospheric delay has always been an important issue in GNSS/DORIS/VLBI/InSAR processing. Most commonly used empirical models for the determination of tropospheric Zenith Hydrostatic Delay (ZHD), including three meteorological models and two empirical ZHD models, are carefully analyzed in this paper. Meteorological models refer to UNB3m, GPT2 and GPT2w, while ZHD models include Hopfield and Saastamoinen. By reference to in-situ meteorological measurements and ray-traced ZHD values of 91 globally distributed radiosonde sites, over a four-years period from 2010 to 2013, it is found that there is strong correlation between errors of model-derived values and latitudes. Specifically, the Saastamoinen model shows a systematic error of about −3 mm. Therefore a modified Saastamoinen model is developed based on the “best average” refractivity constant, and is validated by radiosonde data. Among different models, the GPT2w and the modified Saastamoinen model perform the best. ZHD values derived from their combination have a mean bias of −0.1 mm and a mean RMS of 13.9 mm. Limitations of the present models are discussed and suggestions for further improvements are given. Numéro de notice : A2016-593 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://dx.doi.org/10.1016/j.asr.2016.05.055 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81750 [article]

A high-quality reprocessed ground-based GPS dataset for atmospheric process studies, radiosonde and model evaluation, and reanalysis of HyMeX Special Observing Period / Olivier Bock in Quarterly Journal of the Royal Meteorological Society, vol 142 n° S1 (August 2016)  

Public [article]  inQuarterly Journal of the Royal Meteorological Society > vol 142 n° S1 (August 2016) . - pp 56 - 71 Titre : A high-quality reprocessed ground-based GPS dataset for atmospheric process studies, radiosonde and model evaluation, and reanalysis of HyMeX Special Observing Period Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Pierre Bosser , Auteur ; R. Pacione, Auteur ; Mathieu Nuret, Auteur ; Nadia Fourrié, Auteur ; Ana-Claudia Parracho, Auteur Année de publication : 2016 Article en page(s) : pp 56 - 71 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] atmosphère terrestre [Termes descripteurs IGN] coordonnées GPS [Termes descripteurs IGN] données météorologiques [Termes descripteurs IGN] Méditerranée, mer [Termes descripteurs IGN] modèle atmosphérique [Termes descripteurs IGN] modèle météorologique [Termes descripteurs IGN] prévision météorologique [Termes descripteurs IGN] radiosondage [Termes descripteurs IGN] retard troposphérique zénithal [Termes descripteurs IGN] teneur intégré en vapeur d'eau Résumé : (auteur) In the framework of the Hydrological cycle in the Mediterranean Experiment (HyMeX) project, measurements from more than 1000 ground-based Global Positioning System (GPS) receivers located in the northwestern Mediterranean area are reprocessed using a single piece of GPS software for the period from 1 September 2012 to 31 March 2013. A special screening procedure is developed for the removal of outliers in the GPS Zenith Total Delay (ZTD) data. ZTD data are converted to integrated water vapour (IWV) using surface pressure information from an AROME-WMED operational analysis. The reprocessed ZTD and IWV data are used to assess the accuracy of the near-real time E-GVAP ZTD data assimilated in operational numerical weather prediction systems and to validate the IWV data from the AROME-WMED operational analysis and AROME-WMED reanalysis 1, and from radiosonde observations. The mean differences between E-GVAP and reprocessed ZTD data are not negligible and lie in the range from −3 to +3 mm. The standard deviations of differences are between 4 and 8 mm. The comparisons of IWV from AROME-WMED analyses and the reprocessed GPS data show high quality of the analyses where operational GPS data are assimilated and lower quality where no GPS data are assimilated. Small but significant biases are found in the radiosonde data during daytime (−0.5 to +1.4 kg m−2), but their origin is not determined so far. Thanks to the high spatial density of the reprocessed GPS stations, both the large-scale and small-scale variations in IWV can be documented. The case of HyMeX Intensive Observing Period 8 is presented as an example of a heavy precipitation event. This work suggests that improved quality of the humidity fields can be expected of the future AROME-WMED reanalysis 2 as a result of the assimilation of the reprocessed GPS data. Numéro de notice : A2016-938 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1002/qj.2701 date de publication en ligne : 04/11/2015 En ligne : http://dx.doi.org/10.1002/qj.2701 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83370 [article]

Comparative analysis of real-time precise point positioning zenith total delay estimates / F.A. Ahmed in GPS solutions, vol 20 n° 2 (April 2016)  

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Correction troposphérique des interférogrammes issus d’images radar par mesures GNSS et modèle global d’atmosphère / Vincent Dubreuil (2016)

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Modeling and sensing the vertical structure of the atmospheric path delay by microwave radiometry to correct SAR interferograms / Patrizia Basili in IEEE Transactions on geoscience and remote sensing, vol 52 n° 2 (February 2014)

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Modélisation de la propagation troposphérique des signaux de positionnement par satellites : un tour d'horizon / Camille Desjardins (2014) 

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Are numerical weather model outputs helpful to reduce tropospheric delay signals in InSAR data? / Youhei Kinoshita in Journal of geodesy, vol 87 n° 3 (March 2013)  

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Experimental study on the atmospheric delay based on GPS, SAR Interferometry, and numerical weather model data / P. Mateus in IEEE Transactions on geoscience and remote sensing, vol 51 n° 1 Tome 1 (January 2013)  

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Zenith delay correction with GPT2w / Grégory Pain (2013) 

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Near real-time estimation of water vapour in the troposphere using ground GNSS and the meteorological data / Jaroslaw Bosy in Annales Geophysicae, n° 30 (27/09/2012) 

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Modeling atmospheric refraction influences by optical turbulences using an image-assisted total station / A. Reiterer in ZFV, Zeitschrift für Geodäsie, Geoinformation und Landmanagement, vol 137 n° 3 (01/06/2012)

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Comparison of ray-tracing packages for troposphere delays / V. Nafisi in IEEE Transactions on geoscience and remote sensing, vol 50 n° 2 (February 2012)  

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