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Consistency and analysis of ionospheric observables obtained from three precise point positioning models / Yan Xiang in Journal of geodesy, vol 93 n° 8 (August 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 8 (August 2019) . - pp 1161–1170 Titre : Consistency and analysis of ionospheric observables obtained from three precise point positioning models Type de document : Article/Communication Auteurs : Yan Xiang, Auteur ; Yang Gao, Auteur ; Junbo Shi, Auteur ; Chaoqian Xu, Auteur Année de publication : 2019 Article en page(s) : pp 1161–1170 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] cohérence géométrique [Termes IGN] erreur de positionnement [Termes IGN] erreur en altitude [Termes IGN] erreur systématique [Termes IGN] mesurage de phase [Termes IGN] modèle ionosphérique [Termes IGN] positionnement différentiel [Termes IGN] positionnement ponctuel précis [Termes IGN] propagation ionosphérique Résumé : (auteur) Ionospheric observables based on Global Navigation Satellite System can be obtained by a variety of approaches. The most widely used one is the geometry-free combination of carrier-phase smoothed code measurements. This method, however, introduces leveling errors that substantially degrade the performance of ionospheric modeling and bias estimation. To reduce leveling errors, precise point positioning (PPP) model is preferred for obtaining the ionospheric observables. We aim to investigate whether the ionospheric observables obtained from three different PPP models are consistent and how the PPP-based ionospheric observables relates to the smoothed code method. The paper begins by formulating the ionospheric observables. We then explain the statistical evaluation methods used for analyzing the bias terms derived from these methods and assessing the leveling errors from the carrier-phase smoothed code method. Numerical analysis is then conducted to compare the bias terms in the ionospheric observables and evaluate the leveling errors. The ionospheric observables based on the three PPP models show strong consistency. Compared to leveling errors in the carrier-phase smoothed code method, the leveling errors using the uncombined PPP model are significantly reduced up to five times. Numéro de notice : A2019-384 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-019-01233-1 Date de publication en ligne : 12/02/2019 En ligne : https://doi.org/10.1007/s00190-019-01233-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93463 [article]

GPS real-time precise point positioning for aerial triangulation / Junbo Shi in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 405 – 414 Titre : GPS real-time precise point positioning for aerial triangulation Type de document : Article/Communication Auteurs : Junbo Shi, Auteur ; Xiuxiao Yuan, Auteur ; Yang Cai, Auteur ; Gaojing Wang, Auteur Année de publication : 2017 Article en page(s) : pp 405 – 414 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] aérotriangulation [Termes IGN] antenne [Termes IGN] coordonnées GNSS [Termes IGN] point de vérification [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis Résumé : (auteur) We extend the application of real-time kinematic PPP to aerial triangulation using GPS to determine coordinates of the antenna installed on the airplane, using real-time satellite products from IGS and the CNES Analysis Center. In order to verify the performance of real-time kinematic PPP for aerial triangulation, three tests with varying aerial and ground conditions are assessed. Numerical results show that real-time kinematic PPP using IGS real-time products of 5-cm orbit accuracy and 0.1- to 0.3-ns clock precision can provide comparable accuracy for aerial photogrammetric mapping at the scale of 1:1000 as does post-mission kinematic PPP using IGS final products. Millimeter-to-centimeter-level differences and centimeter-to-2-decimeter differences are identified for horizontal and vertical coordinates of ground check points, respectively, in the three tests. The comparison between real-time IGS and CNES products for GPS positioning and aerial triangulation unveils that real-time products with a better clock precision can result in better performance of GPS real-time kinematic PPP as applied to aerial triangulation. Numéro de notice : A2017-248 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0532-2 En ligne : http://dx.doi.org/10.1007/s10291-016-0532-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85055 [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 IGN] analyse comparative [Termes IGN] erreur systématique [Termes IGN] évaluation [Termes IGN] modèle atmosphérique [Termes IGN] modèle numérique [Termes IGN] radiosondage [Termes IGN] retard troposphérique [Termes 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 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2016.05.055 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]

Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation / Junbo Shi in Journal of geodesy, vol 89 n° 8 (August 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 8 (August 2015) . - pp 747-756 Titre : Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation Type de document : Article/Communication Auteurs : Junbo Shi, Auteur ; Chaoqian Xu, Auteur ; Yihe Li, Auteur ; Yang Gao, Auteur Année de publication : 2015 Article en page(s) : pp 747-756 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] erreur corrélée au temps [Termes IGN] horloge atomique [Termes IGN] orbite précise [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] retard troposphérique zénithal [Termes IGN] temps réel [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Global Positioning System (GPS) has become a cost-effective tool to determine troposphere zenith total delay (ZTD) with accuracy comparable to other atmospheric sensors such as the radiosonde, the water vapor radiometer, the radio occultation and so on. However, the high accuracy of GPS troposphere ZTD estimates relies on the precise satellite orbit and clock products available with various latencies. Although the International GNSS Service (IGS) can provide predicted orbit and clock products for real-time applications, the predicted clock accuracy of 3 ns cannot always guarantee the high accuracy of troposphere ZTD estimates. Such limitations could be overcome by the use of the newly launched IGS real-time service which provides ∼5 cm orbit and 0.2–1.0 ns (an equivalent range error of 6–30 cm) clock products in real time. Considering the relatively larger magnitude of the clock error than that of the orbit error, this paper investigates the effect of real-time satellite clock errors on the GPS precise point positioning (PPP)-based troposphere ZTD estimation. Meanwhile, how the real-time satellite clock errors impact the GPS PPP-based troposphere ZTD estimation has also been studied to obtain the most precise ZTD solutions. First, two types of real-time satellite clock products are assessed with respect to the IGS final clock product in terms of accuracy and precision. Second, the real-time GPS PPP-based troposphere ZTD estimation is conducted using data from 34 selected IGS stations over three independent weeks in April, July and October, 2013. Numerical results demonstrate that the precision, rather than the accuracy, of the real-time satellite clock products impacts the real-time PPP-based ZTD solutions more significantly. In other words, the real-time satellite clock product with better precision leads to more precise real-time PPP-based troposphere ZTD solutions. Therefore, it is suggested that users should select and apply real-time satellite products with better clock precision to obtain more consistent real-time PPP-based ZTD solutions. Numéro de notice : A2015-374 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0811-7 Date de publication en ligne : 04/04/2015 En ligne : https://doi.org/10.1007/s00190-015-0811-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76852 [article]

Real-time GPS precise point positioning-based precipitable water vapor estimation for rainfall monitoring and forecasting / Junbo Shi in IEEE Transactions on geoscience and remote sensing, vol 53 n° 6 (June 2015)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 53 n° 6 (June 2015) . - pp 3452 - 3459 Titre : Real-time GPS precise point positioning-based precipitable water vapor estimation for rainfall monitoring and forecasting Type de document : Article/Communication Auteurs : Junbo Shi, Auteur ; Chaoqian Xu, Auteur ; Jiming Guo, Auteur ; Yang Gao, Auteur Année de publication : 2015 Article en page(s) : pp 3452 - 3459 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] estimation statistique [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] précipitation [Termes IGN] prévision météorologique [Termes IGN] surveillance météorologique [Termes IGN] vapeur d'eau Résumé : (Auteur) GPS-based precipitable water vapor (PWV) estimation has been proven as a cost-effective approach for numerical weather prediction. Most previous efforts focus on the performance evaluation of post-processed GPS-derived PWV estimates using International GNSS Service (IGS) satellite products with at least 3-9-h latency. However, the suggested timeliness for meteorological nowcasting is 5-30 min. Therefore, the latency has limited the GPS-based PWV estimation in real-time meteorological nowcasting. The limitation has been overcome since April 2013 when IGS released real-time GPS orbit and clock products. This becomes the focus of this paper, which investigates real-time GPS precise point positioning (PPP)-based PWV estimation and its potential for rainfall monitoring and forecasting. This paper first evaluates the accuracy of IGS CLK90 real-time orbit and clock products. Root-mean-square (RMS) errors of Numéro de notice : A2015-279 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2014.2377041 Date de publication en ligne : 22/12/2014 En ligne : https://doi.org/10.1109/TGRS.2014.2377041 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76390 [article]

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Overview of FY-3 payload and ground application system / Z. Yang in IEEE Transactions on geoscience and remote sensing, vol 50 n° 12 (December 2012)  

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