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Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations / Xulei Jin in Journal of geodesy, vol 97 n° 3 (March 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 3 (March 2023) . - n° 27 Titre : Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations Type de document : Article/Communication Auteurs : Xulei Jin, Auteur ; Shuli Song, Auteur Année de publication : 2023 Article en page(s) : n° 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] carte ionosphérique mondiale [Termes IGN] données Jason [Termes IGN] modèle ionosphérique [Termes IGN] temps réel [Termes IGN] teneur totale en électrons [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) For the purposes of routinely providing reliable and low-latency Global Ionosphere Maps (GIMs), a method of estimating hourly updated near real-time GIM with a time latency of about 1–2 h based on a 24-h data sliding window of Global Navigation Satellite System (GNSS) near real-time observations and real-time data streams was presented. On the basis of the implementation of near real-time GIM estimation, an hourly updated GIM nowcasting method was further proposed to improve the accurate of short-term total electron content (TEC) prediction. We estimated the Shanghai Astronomical Observatory near real-time GIM (SHUG) and nowcasting GIM (SHPG) in the solar relatively active year (2014) and quiet year (2021), and employed GIMs provided by the International GNSS Service, the Global Positioning System (GPS) differential slant TECs (dSTECs) extracted from global independent GNSS stations, and the vertical TECs (VTECs) inverted from satellite altimetry as the references to validate the estimated results. The GPS dSTECs evaluation results show that SHUG behaves fairly consistent with the rapid GIMs, with a discrepancy of less than 1 TEC unit (TECu) overall. The standard deviations (STDs) of SHUG with respect to Jason-2/-3 VTECs are no more than 10% over the majority of rapid GIMs due to the instability of observations. The performance of 1-h nowcasting SHPG is significantlybetter than the Center for Orbit Determination in Europe (CODE) 1-day predicted GIM (C1PG). GPS dSTEC validation results indicate that 1-h nowcasting SHPG is 1 to 2 TECu more reliable than C1PG in eventful ionospheric electron activity regions, and it outperforms the C1PG by 10% overall versus Jason-2/-3 VTECs. The hourly updated SHUG and SHPG have relatively high reliability and low time latency, and thus can provide excellent service for (near) real-time users and offer more accurate TEC background information than daily predicted GIM for real-time GIM estimation. Numéro de notice : A2023-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01715-3 Date de publication en ligne : 20/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01715-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102950 [article]

Temporal spectrum of spatial correlations between GNSS station position time series / Yujiao Niu in Journal of geodesy, vol 97 n° 2 (February 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 2 (February 2023) . - n° 12 Titre : Temporal spectrum of spatial correlations between GNSS station position time series Type de document : Article/Communication Auteurs : Yujiao Niu, Auteur ; Paul Rebischung , Auteur ; Min Li, Auteur ; Na Wei, Auteur ; Chuang Shi, Auteur ; Zuheir Altamimi , Auteur Année de publication : 2023 Article en page(s) : n° 12 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse spatio-temporelle [Termes IGN] bruit blanc [Termes IGN] corrélation automatique de points homologues [Termes IGN] filtrage du bruit [Termes IGN] série temporelle [Termes IGN] station GNSS [Termes IGN] transformation de Fourier [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) The background noise in Global Navigation Satellite Systems (GNSS) station position time series is known to be both temporally and spatially correlated. Its temporal correlations are well modeled and routinely taken into account when deriving parameters of interest like station velocities. On the other hand, a general model of the spatial correlations in GNSS time series is lacking, and they are usually ignored, although their consideration could benefit several purposes such as offset detection, velocity estimation or spatial filtering. In order to improve the realism of current spatio-temporal correlation models, we investigate in this study how the spatial correlations of GNSS time series vary with the temporal frequency. A frequency-dependent measure of the spatial correlations is therefore introduced and applied to station position time series from the latest reprocessing campaign of the International GNSS Service (IGS), as well as to Precise Point Positioning time series provided by the Nevada Geodetic Laboratory (NGL). Different spatial correlation regimes are thus evidenced at different temporal frequencies. The different levels of spatial correlations between IGS and NGL datasets furthermore suggest that some part of the spatially correlated background noise in GNSS time series consists of GNSS errors rather than aperiodic Earth surface deformation signal. Numéro de notice : A2023-226 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01703-7 Date de publication en ligne : 06/02/2023 En ligne : https://doi.org/10.1007/s00190-023-01703-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102746 [article]

Identifying spurious cycle slips based on iterative filtering under disturbed ionospheric conditions for undifferenced GNSS observations / Yan Xiang in Advances in space research, vol 70 n° 11 (December 2022)  

Public [article]  inAdvances in space research > vol 70 n° 11 (December 2022) . - pp 3582 - 3593 Titre : Identifying spurious cycle slips based on iterative filtering under disturbed ionospheric conditions for undifferenced GNSS observations Type de document : Article/Communication Auteurs : Yan Xiang, Auteur ; Sijie Lyu, Auteur ; Wenxian Yu, Auteur Année de publication : 2022 Article en page(s) : pp 3582 - 3593 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] erreur de positionnement [Termes IGN] filtre [Termes IGN] glissement de cycle [Termes IGN] itération [Termes IGN] perturbation ionosphérique [Termes IGN] phase GNSS [Termes IGN] positionnement ponctuel précis [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) The TurboEdit method is widely used to detect cycle slips on the global navigation satellite system (GNSS) carrier-phase measurements. However, it leads to an increasing number of false alarms in detecting cycle slips under disturbed ionospheric conditions. Besides, once the method detects a cycle slip at one satellite, it treats dual frequencies with cycle slips rather than at one frequency. Considering these two challenges, we developed a solution-based iterative filter detection method to reduce the number of spurious cycle slip detection under disturbed ionospheric conditions. The method initially assumes that there is no cycle slip at each frequency. We then estimate the solutions without cycle slips. A decision of exiting cycle slips is made by examining and comparing the two results solutions with or without cycle slips in terms of usable satellites, ambiguities, and residuals. The uncombined precise point positioning (PPP) during disturbed ionospheric conditions on 17 March 2015 at high latitude was studied to validate the proposed method. Results showed that the detected number of spurious cycle slips was reduced significantly. With fewer marked cycle slips, more stable and smoother positioning performance was achieved when fewer ambiguity parameters were reinitialized. Numéro de notice : A2022-861 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1016/j.asr.2022.08.008 Date de publication en ligne : 08/08/2022 En ligne : https://doi.org/10.1016/j.asr.2022.08.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102144 [article]

A determination of the motion based on GNSS observations between 2000 and 2021 using the IGS points in the polar regions / Atinç Pirti in Geodesy and cartography, vol 48 n° 3 (October 2022)  

Public [article]  inGeodesy and cartography > vol 48 n° 3 (October 2022) . - pp 177 - 184 Titre : A determination of the motion based on GNSS observations between 2000 and 2021 using the IGS points in the polar regions Type de document : Article/Communication Auteurs : Atinç Pirti, Auteur Année de publication : 2022 Article en page(s) : pp 177 - 184 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse diachronique [Termes IGN] Antarctique [Termes IGN] Arctique [Termes IGN] données GNSS [Termes IGN] international GPS service for geodynamics [Termes IGN] International Terrestrial Reference Frame [Termes IGN] mouvement du pôle [Termes IGN] réseau géodésique [Termes IGN] série temporelle [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) People are fascinated today more than ever by the polar regions of the Earth. One reason for this is that wide expanses of the Arctic and Antarctic have not been explored and are therefore still viewed as frontier regions. Another is that they both have very diverse histories with regard to their origins and ice formation. Their numerous aspects still pose many puzzles for science today. The regions of the Earth designated as polar are those areas located between the North or South Pole and the Arctic or Antarctic Circles, respectively. The northern polar region, called the Arctic, encompasses the Arctic Ocean and a portion of some surrounding land masses. The southern polar region, called the Antarctic, contains the continent of Antarctica and areas of the surrounding Southern Ocean. In this paper three tests (2000, 2010 and 2021) of continuous GNSS data recorded by 8 permanent International GPS Service (IGS) stations in both Polar Regions have been processed by using CSRS-PPP Software for geodetic networks. The results also show that all GNSS provide good visibility with low elevation angles, whereas with high elevation angles, which might be needed due to natural barriers, the GLONASS and other satellites provides the highest number of visible satellites. Consequently, the mean motion of the study area was found approximately 7–15 cm for horizontal components (X–Y) and 6 cm for vertical components (Ellipsoidal Height) on the eight IGS points in the both poles. Numéro de notice : A2022-761 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3846/gac.2022.14848 Date de publication en ligne : 02/09/2022 En ligne : https://doi.org/10.3846/gac.2022.14848 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101777 [article]

Modelling and prediction of GNSS time series using GBDT, LSTM and SVM machine learning approaches / Wenzong Gao in Journal of geodesy, vol 96 n° 10 (October 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 10 (October 2022) . - n° 71 Titre : Modelling and prediction of GNSS time series using GBDT, LSTM and SVM machine learning approaches Type de document : Article/Communication Auteurs : Wenzong Gao, Auteur ; Zhao Li, Auteur ; Qusen Chen, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 71 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] classification par réseau neuronal récurrent [Termes IGN] classification par séparateurs à vaste marge [Termes IGN] déformation de la croute terrestre [Termes IGN] données GNSS [Termes IGN] Extreme Gradient Machine [Termes IGN] modèle de simulation [Termes IGN] série temporelle [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Global navigation satellite system (GNSS) site coordinate time series provides essential data for geodynamic and geophysical studies, realisation of a regional or global geodetic reference frames, and crustal deformation research. The coordinate time series has been conventionally modelled by least squares (LS) fitting with harmonic functions, alongside many other analysis methods. As a key limitation, the traditional modelling approaches simply use the functions of time variable, despite good knowledge of various underlying physical mechanisms responsible for the site displacements. This paper examines the use of machine learning (ML) models to reflect the effects or residential effects of physical variables related to Sun and the Moon ephemerides, polar motion, temperature, atmospheric pressure, and hydrology on the site displacements. To form the ML problem, these variables are constructed as the input vector of each ML training sample, while the vertical displacement of a GNSS site is regarded as the output value. In the evaluation experiments, three ML approaches, namely the gradient boosting decision tree (GBDT) approach, long short-term memory (LSTM) approach, and support vector machine (SVM) approach, are introduced and evaluated with the time series datasets collected from 9 GNSS sites over the period of 13 years. The results indicate that all three approaches achieve similar fitting precision in the range of 3–5 mm in the vertical displacement component, which is an improvement in over 30% with respect to the traditional LS fitting precision in the range of 4–7 mm. The prediction of the vertical time series with the three ML approaches shows the precision in the range of 4–7 mm over the future 24- month period. The results also indicate the relative importance of different physical features causing the displacements of each site. Overall, ML approaches demonstrate better performance and effectiveness in modelling and prediction of GNSS time series, thus impacting maintenance of geodetic reference frames, geodynamics, geophysics, and crustal deformation analysis. Numéro de notice : A2022-737 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01662-5 Date de publication en ligne : 27/09/2022 En ligne : https://doi.org/10.1007/s00190-022-01662-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101709 [article]

Integration of GNSS observations with volunteered geographic information for improved navigation performance / Tarek Hassan in Journal of applied geodesy, vol 16 n° 3 (July 2022)  

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Outliers and uncertainties in GNSS ZTD estimates from double-difference processing and precise point positioning / Katarzyna Stępniak in GPS solutions, vol 26 n° 3 (July 2022)  

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GNSS observable-specific phase biases for all-frequency PPP ambiguity resolution / Jianghui Geng in Journal of geodesy, vol 96 n° 2 (February 2022)  

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Ionospheric tomographic common clock model of undifferenced uncombined GNSS measurements / German Olivares-Pulido in Journal of geodesy, vol 95 n° 11 (November 2021)  

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A mean-squared-error condition for weighting ionospheric delays in GNSS baselines / Peter J.G. Teunissen in Journal of geodesy, vol 95 n° 11 (November 2021)  

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Visualization of GNSS multipath effects and its potential application in IGS data processing / Weiming Tang in Journal of geodesy, vol 95 n° 9 (September 2021)  

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Estimation of code observation-specific biases (OSBs) for the modernized multi-frequency and multi-GNSS signals: an undifferenced and uncombined approach / Teng Liu in Journal of geodesy, vol 95 n° 8 (August 2021)  

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Impact of observation sampling rate on multi-GNSS static PPP performance / Berkay Bahadur in Survey review, Vol 53 n° 378 (May 2021)  

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A highly adaptable method for GNSS cycle slip detection and repair based on Kalman filter / Xianwen Yu in Survey review, Vol 53 n° 377 (February 2021)  

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Stochastic model reliability in GNSS baseline solution / Aviram Borko in Journal of geodesy, vol 95 n° 2 (February 2021)  

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