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Integrity investigation of global ionospheric TEC maps for high-precision positioning / Jiaojiao Zhao in Journal of geodesy, vol 95 n° 3 (March 2021)  

Public [article]  inJournal of geodesy > vol 95 n° 3 (March 2021) . - n° 35 Titre : Integrity investigation of global ionospheric TEC maps for high-precision positioning Type de document : Article/Communication Auteurs : Jiaojiao Zhao, Auteur ; Manuel Hernández-Pajares, Auteur ; Ningbo Wang, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 35 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] carte ionosphérique mondiale [Termes IGN] erreur moyenne quadratique [Termes IGN] International GNSS Service [Termes IGN] modèle ionosphérique [Termes IGN] modèle stochastique [Termes IGN] positionnement ponctuel précis [Termes IGN] tempête magnétique [Termes IGN] teneur totale en électrons Résumé : (auteur) Aside from the ionospheric total electron content (TEC) information, root-mean-square (RMS) maps are also provided as the standard deviations of the corresponding TEC errors in global ionospheric maps (GIMs). As the RMS maps are commonly used as the accuracy indicator of GIMs to optimize the stochastic model of precise point positioning algorithms, it is of crucial importance to investigate the reliability of RMS maps involved in GIMs of different Ionospheric Associated Analysis Centers (IAACs) of the International GNSS Service (IGS), i.e., the integrity of GIMs. We indirectly analyzed the reliability of RMS maps by comparing the actual error of the differential STEC (dSTEC) with the RMS of the dSTEC derived from the RMS maps. With this method, the integrity of seven rapid IGS GIMs (UQRG, CORG, JPRG, WHRG, EHRG, EMRG, and IGRG) and six final GIMs (UPCG, CODG, JPLG, WHUG, ESAG and IGSG) was examined under the maximum and minimum solar activity conditions as well as the geomagnetic storm period. The results reveal that the reliability of the RMS maps is significantly different for the GIMs from different IAACs. Among these GIMs, the values in the RMS maps of UQRG are large, which can be used as ionospheric protection level, while the RMS values in EHRG and ESAG are significantly lower than the realistic RMS. The rapid and final GIMs from CODE, JPL and WHU provide quite reasonable RMS maps. The bounding performance of RMS maps can be influenced by the location of the stations, while the influence of solar activity and the geomagnetic storm is not obvious. Numéro de notice : A2021-220 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01487-8 Date de publication en ligne : 22/02/2021 En ligne : https://doi.org/10.1007/s00190-021-01487-8 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97188 [article]

Assessing the quality of ionospheric models through GNSS positioning error: methodology and results / Adria Rovira-Garcia in GPS solutions, vol 24 n° 1 (January 2020)  

Public [article]  inGPS solutions > vol 24 n° 1 (January 2020) Titre : Assessing the quality of ionospheric models through GNSS positioning error: methodology and results Type de document : Article/Communication Auteurs : Adria Rovira-Garcia, Auteur ; Deimos Ibáñez-Segura, Auteur ; Raül Orús-Pérez, Auteur ; et al., Auteur Année de publication : 2020 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] erreur de positionnement [Termes IGN] International GNSS Service [Termes IGN] modèle ionosphérique [Termes IGN] phase [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] retard ionosphèrique [Termes IGN] trajet multiple [Termes IGN] valeur aberrante Résumé : (Auteur) Single-frequency users of the global navigation satellite system (GNSS) must correct for the ionospheric delay. These corrections are available from global ionospheric models (GIMs). Therefore, the accuracy of the GIM is important because the unmodeled or incorrectly part of ionospheric delay contributes to the positioning error of GNSS-based positioning. However, the positioning error of receivers located at known coordinates can be used to infer the accuracy of GIMs in a simple manner. This is why assessment of GIMs by means of the position domain is often used as an alternative to assessments in the ionospheric delay domain. The latter method requires accurate reference ionospheric values obtained from a network solution and complex geodetic modeling. However, evaluations using the positioning error method present several difficulties, as evidenced in recent works, that can lead to inconsistent results compared to the tests using the ionospheric delay domain. We analyze the reasons why such inconsistencies occur, applying both methodologies. We have computed the position of 34 permanent stations for the entire year of 2014 within the last Solar Maximum. The positioning tests have been done using code pseudoranges and carrier-phase leveled (CCL) measurements. We identify the error sources that make it difficult to distinguish the part of the positioning error that is attributable to the ionospheric correction: the measurement noise, pseudorange multipath, evaluation metric, and outliers. Once these error sources are considered, we obtain equivalent results to those found in the ionospheric delay domain assessments. Accurate GIMs can provide single-frequency navigation positioning at the decimeter level using CCL measurements and better positions than those obtained using the dual-frequency ionospheric-free combination of pseudoranges. Finally, some recommendations are provided for further studies of ionospheric models using the position domain method. Numéro de notice : A2020-024 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-019-0918-z Date de publication en ligne : 02/11/2019 En ligne : https://doi.org/10.1007/s10291-019-0918-z Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94468 [article]

Position, navigation, and timing technologies in the 21st century: Integrated satellite navigation, sensor systems, and civil applications, ch. 27. Global geodesy and reference frames / Chris Rizos (2020)  

Public Titre de série : Position, navigation, and timing technologies in the 21st century: Integrated satellite navigation, sensor systems, and civil applications, ch. 27 Titre : Global geodesy and reference frames Type de document : Chapitre/Contribution Auteurs : Chris Rizos, Auteur ; Zuheir Altamimi , Auteur ; Gary Johnson, Auteur Editeur : New York, Londres, Hoboken (New Jersey), ... : John Wiley & Sons Année de publication : 2020 Projets : 1-Pas de projet / Importance : pp 717 - 739 Note générale : in Position, Navigation, and Timing Technologies in the 21st Century: Integrated Satellite Navigation, Sensor Systems, and Civil Applications, Volume 1 - Editor(s): Y. T. Jade Morton, Frank van Diggelen, James J. Spilker Jr., Bradford W. Parkinson, Sherman Lo, Grace Gao - First published: 15 December 2020 - Print ISBN:9781119458418 | Online ISBN: 9781119458449 | DOI: 10.1002/9781119458449 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] International GNSS Service [Termes IGN] International Terrestrial Reference Frame [Termes IGN] positionnement par GNSS Résumé : (auteur) This chapter is organized into three parts. The first part is an introduction to space geodesy, the principles of global navigation satellite system (GNSS) geodesy, and the International Association of Geodesy (IAG). The IAG is the scientific association that organizes the space geodetic services that support high‐accuracy GNSS positioning for scientific and societal applications. The most important of the IAG services is the International GNSS Service (IGS), and the second part of the chapter provides a short description of the IGS and its role in providing the geodetic infrastructure and services that underpin precision GNSS positioning. The third part describes one of the most important products of modern geodesy, the Terrestrial Reference Frame (TRF). The chapter also provides a brief explanation of how the International TRF is realized, including some information on the current ITRF2014. Numéro de notice : H2020-004 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Chapître / contribution nature-HAL : ChOuvrScient DOI : 10.1002/9781119458449.ch27 Date de publication en ligne : 15/12/2020 En ligne : https://doi.org/10.1002/9781119458449.ch27 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96825

Combined orbits and clocks from IGS second reprocessing / Jake Griffiths in Journal of geodesy, vol 93 n° 2 (February 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 2 (February 2019) . - pp 177 - 195 Titre : Combined orbits and clocks from IGS second reprocessing Type de document : Article/Communication Auteurs : Jake Griffiths, Auteur Année de publication : 2019 Article en page(s) : pp 177 - 195 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] données GLONASS [Termes IGN] données GPS [Termes IGN] horloge du satellite [Termes IGN] International GNSS Service [Termes IGN] International Terrestrial Reference Frame [Termes IGN] orbite [Termes IGN] positionnement ponctuel précis [Termes IGN] série temporelle [Termes IGN] traitement de données GNSS Résumé : (auteur) The Analysis Centers (ACs) of the International GNSS Service (IGS) have reprocessed a large global network of GPS tracking data from 1994.0 until 2014.0 or later. Each AC product time series was extended uniformly till early 2015 using their weekly operational IGS contributions so that the complete combined product set covers GPS weeks 730 through 1831. Three ACs also included GLONASS data from as early as 2002 but that was insufficient to permit combined GLONASS products. The reprocessed terrestrial frame combination procedures and results have been reported already, and those were incorporated into the ITRF2014 multi-technique global frame released in 2016. This paper describes the orbit and clock submissions and their multi-AC combinations and assessments. These were released to users in early 2017 in time for the adoption of IGS14 for generating the operational IGS products. While the reprocessing goal was to enable homogeneous modeling, consistent with the current operational procedures, to be applied retrospectively to the full history of observation data in order to achieve a more suitable reference for geophysical studies, that objective has only been partially achieved. Ongoing AC analysis changes and a lack of full participation limit the consistency and precision of the finished IG2 products. Quantitative internal measures indicate that the reprocessed orbits are somewhat less precise than current operational orbits or even the later orbits from the first IGS reprocessing campaign. That is even more apparent for the clocks where a lack of robust AC participation means that it was only possible to form combined 5-min clocks but not the 30-s satellite clocks published operationally. Therefore, retrospective precise point positioning solutions by users are not recommended using the orbits and clocks. Nevertheless, the orbits do support long-term stable user solutions when used with network processing with either double differencing or explicit clock estimation. Among the main benefits of the reprocessing effort is a more consistent long product set to analyze for sources of systematic error and accuracy. Work to do that is underway but the reprocessing experience already points to a number of ways future IGS performance and reprocessing campaigns can be improved. Numéro de notice : A2019-078 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1149-8 Date de publication en ligne : 18/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1149-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92196 [article]

IGS polar motion measurement accuracy / Jim Ray in Geodesy and Geodynamics, vol 8 n° 6 (November 2017)    

Public [article]  inGeodesy and Geodynamics > vol 8 n° 6 (November 2017) . - pp 413 - 420 Titre : IGS polar motion measurement accuracy Type de document : Article/Communication Auteurs : Jim Ray, Auteur ; Paul Rebischung , Auteur ; Jake Griffiths, Auteur Année de publication : 2017 Projets : 1-Pas de projet / Article en page(s) : pp 413 - 420 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] données GPS [Termes IGN] erreur systématique [Termes IGN] International GNSS Service [Termes IGN] mouvement du pôle [Termes IGN] orientation de la Terre [Termes IGN] paramètres d'orientation de la Terre [Termes IGN] précision du positionnement Résumé : (auteur) We elaborate an error budget for the long-term accuracy of IGS (International Global Navigation Satellite System Service) polar motion estimates, concluding that it is probably about 25–30 μas (1-sigma) overall, although it is not possible to quantify possible contributions (mainly annual) that might transfer directly from aliases of subdaily rotational tide errors. The leading sources are biases arising from the need to align daily, observed terrestrial frames, within which the pole coordinates are expressed and which are continuously deforming, to the secular, linear international reference frame. Such biases are largest over spans longer than about a year. Thanks to the very large number of IGS tracking stations, the formal covariance errors are much smaller, around 5 to 10 μas. Large networks also permit the systematic frame-related errors to be more effectively minimized but not eliminated. A number of periodic errors probably also influence polar motion results, mainly at annual, GPS (Global Positioning System) draconitic, and fortnightly periods, but their impact on the overall error budget is unlikely to be significant except possibly for annual tidal aliases. Nevertheless, caution should be exercised in interpreting geophysical excitations near any of the suspect periods. Numéro de notice : A2017-253 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.geog.2017.01.008 Date de publication en ligne : 02/03/2017 En ligne : https://doi.org/10.1016/j.geog.2017.01.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85261 [article]

Documents numériques

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Maintaining real-time precise point positioning during outages of orbit and clock corrections / Ahmed El-Mowafy in GPS solutions, vol 21 n° 3 (July 2017)  

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Ionospheric error contribution to GNSS single-frequency navigation at the 2014 solar maximum / Raul Orus Perez in Journal of geodesy, vol 91 n° 4 (April 2017)  

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The international GNSS monitoring and assessment service in a multi-system environment / Echoda Ngbede Joshua Ada in Inside GNSS, vol 11 n° 4 (July - August 2016)  

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Global optimization of GNSS station reference networks / David Coulot in GPS solutions, vol 19 n° 4 (october 2015)  

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CODE’s new solar radiation pressure model for GNSS orbit determination / Daniel Arnold in Journal of geodesy, vol 89 n° 8 (August 2015)  

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Performance analysis of GPS/GLONASS precise point positioning / Mohamed Azab in Geomatica, vol 67 n° 4 (December 2013)  

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Dependence of IGS products on the ITRF datum / Jim Ray (2013)  

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Recent results from the IGS terrestrial frame combinations / Paul Rebischung (2013)  

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Galileo and GNSS to the fore: Activities of the European navigation support office / W. Enderle in GPS world, vol 23 n° 12 (December 2012)

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Zero-difference GPS ambiguity resolution at CNES–CLS IGS Analysis Center / Sylvain Loyer in Journal of geodesy, vol 86 n° 11 (November 2012)  

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