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Visual analytics of time-varying multivariate ionospheric scintillation data / Aurea Soriano-Vargas in Computers and graphics, vol 68 (November 2017)  

Public [article]  inComputers and graphics > vol 68 (November 2017) . - pp 96 - 107 Titre : Visual analytics of time-varying multivariate ionospheric scintillation data Type de document : Article/Communication Auteurs : Aurea Soriano-Vargas, Auteur ; Bruno C. Vani, Auteur ; Milton H. Shimabukuro, Auteur ; João F.G. Monico, Auteur Année de publication : 2017 Article en page(s) : pp 96 - 107 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse géovisuelle [Termes IGN] analyse multivariée [Termes IGN] données spatiotemporelles [Termes IGN] ionosphère [Termes IGN] scintillation [Termes IGN] visualisation de données [Vedettes matières IGN] Géovisualisation Résumé : (résumé) We present a clustering-based interactive approach to multivariate data analysis, motivated by the specific needs of scintillation data. Ionospheric scintillation is a rapid variation in the amplitude and/or phase of radio signals traveling through the ionosphere. This spatial and time-varying phenomenon is of great interest since it affects the reception quality of satellite signals. Specialized receivers at strategic regions can track multiple variables related to this phenomenon, generating a database of observations of regional ionospheric scintillation. We introduce a visual analytics solution to support analysis of such data, keeping in mind the general applicability of our approach to similar multivariate data analysis situations. Taking into account typical user questions, we combine visualization and data mining algorithms that satisfy these goals: (i) derive a representation of the variables monitored that conveys their behavior in detail, at multiple user-defined aggregation levels; (ii) provide overviews of multiple variables regarding their behavioral similarity over selected time periods; (iii) support users when identifying representative variables for characterizing scintillation behavior. We illustrate the capabilities of our proposed framework by presenting case studies driven directly by questions formulated by collaborating domain experts. Numéro de notice : A2017-452 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.cag.2017.08.013 En ligne : https://doi.org/10.1016/j.cag.2017.08.013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86363 [article]

Improving the GNSS positioning stochastic model in the presence of ionospheric scintillation / M. Aquino in Journal of geodesy, vol 83 n° 10 (October 2009)  

Public [article]  inJournal of geodesy > vol 83 n° 10 (October 2009) . - pp 953 - 966 Titre : Improving the GNSS positioning stochastic model in the presence of ionospheric scintillation Type de document : Article/Communication Auteurs : M. Aquino, Auteur ; João F.G. Monico, Auteur ; A.H. Dodson, Auteur ; et al., Auteur Année de publication : 2009 Article en page(s) : pp 953 - 966 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] modèle stochastique [Termes IGN] positionnement par GNSS [Termes IGN] propagation ionosphérique [Termes IGN] récepteur GNSS [Termes IGN] scintillation [Termes IGN] teneur totale en électrons Résumé : (Auteur) Ionospheric scintillations are caused by time- varying electron density irregularities in the ionosphere, occurring more often at equatorial and high latitudes. This paper focuses exclusively on experiments undertaken in Europe, at geographic latitudes between ~50°N and ~80°N, where a network of GPS receivers capable of monitoring Total Electron Content and ionospheric scintillation parameters was deployed. The widely used ionospheric scintillation indices S4 and {\sigma_{\varphi}} represent a practical measure of the intensity of amplitude and phase scintillation affecting GNSS receivers. However, they do not provide sufficient information regarding the actual tracking errors that degrade GNSS receiver performance. Suitable receiver tracking models, sensitive to ionospheric scintillation, allow the computation of the variance of the output error of the receiver PLL (Phase Locked Loop) and DLL (Delay Locked Loop), which expresses the quality of the range measurements used by the receiver to calculate user position. The ability of such models of incorporating phase and amplitude scintillation effects into the variance of these tracking errors underpins our proposed method of applying relative weights to measurements from different satellites. That gives the least squares stochastic model used for position computation a more realistic representation, vis-a-vis the otherwise ‘equal weights’ model. For pseudorange processing, relative weights were com- puted, so that a ‘scintillation-mitigated’ solution could be performed and compared to the (non-mitigated) ‘equal weights’ solution. An improvement between 17 and 38% in height accuracy was achieved when an epoch by epoch differential solution was computed over baselines ranging from 1 to 750 km. The method was then compared with alternative approaches that can be used to improve the least squares stochastic model such as weighting according to satellite elevation angle and by the inverse of the square of the standard deviation of the code/carrier divergence (sigma CCDiv). The influence of multipath effects on the proposed mitigation approach is also discussed. With the use of high rate scintillation data in addition to the scintillation indices a carrier phase based mitigated solution was also implemented and compared with the conventional solution. During a period of occurrence of high phase scintillation it was observed that problems related to ambiguity resolution can be reduced by the use of the proposed mitigated solution. Copyright Springer Numéro de notice : A2009-430 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-009-0313-6 En ligne : https://doi.org/10.1007/s00190-009-0313-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30061 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-09091	SL	Revue	Centre de documentation	Revues en salle	Disponible

The wavelet method as an alternative for reducing ionospheric effects from single-frequency GPS receivers / E.M. DE Souza in Journal of geodesy, vol 81 n° 12 (December 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 12 (December 2007) . - pp 799 - 804 Titre : The wavelet method as an alternative for reducing ionospheric effects from single-frequency GPS receivers Type de document : Article/Communication Auteurs : E.M. DE Souza, Auteur ; João F.G. Monico, Auteur Année de publication : 2007 Article en page(s) : pp 799 - 804 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse multirésolution [Termes IGN] double différence [Termes IGN] perturbation ionosphérique [Termes IGN] récepteur monofréquence [Termes IGN] signal GPS [Termes IGN] transformation en ondelettes Résumé : (Auteur) The ionospheric effect is one of the major errors in GPS data processing over long baselines. As a dispersive medium, it is possible to compute its influence on the GPS signal with the ionosphere-free linear combination of L1 and L2 observables, requiring dual-frequency receivers. In the case of single-frequency receivers, ionospheric effects are either neglected or reduced by using a model. In this paper, an alternative for single-frequency users is proposed. It involves multiresolution analysis (MRA) using a wavelet analysis of the double-difference observations to remove the short- and medium-scale ionosphere variations and disturbances, as well as some minor tropospheric effects. Experiments were carried out over three baseline lengths from 50 to 450 km, and the results provided by the proposed method were better than those from dual-frequency receivers. The horizontal root mean square was of about 0.28 m (1ó). Copyright Springer Numéro de notice : A2007-526 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0150-4 En ligne : https://doi.org/10.1007/s00190-007-0150-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28889 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07101	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07102	RAB	Revue	Centre de documentation	En réserve L003	Disponible