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Potentialities of multifrequency ionospheric correction in Global Navigation Satellite Systems / B. Kim in Journal of geodesy, vol 85 n° 3 (March 2011)  

Public [article]  inJournal of geodesy > vol 85 n° 3 (March 2011) . - pp 159 - 169 Titre : Potentialities of multifrequency ionospheric correction in Global Navigation Satellite Systems Type de document : Article/Communication Auteurs : B. Kim, Auteur ; M. Tinin, Auteur Année de publication : 2011 Article en page(s) : pp 159 - 169 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction ionosphérique [Termes IGN] diffraction [Termes IGN] propagation du signal [Termes IGN] récepteur bifréquence [Termes IGN] récepteur GNSS [Termes IGN] résidu [Termes IGN] traitement de données GNSS [Termes IGN] variance Résumé : (Auteur) The first-order ionospheric error is reduced in the dual-frequency Global Navigation Satellite Systems (GNSS). In this paper, the possibility of eliminating ionospheric higher-order errors in the multifrequency GNSS is explored. Since the second-order error associated with the geomagnetic field effect on the refractive index can be eliminated in dual-frequency measurements, we explore the possibility of eliminating third-order errors in triple-frequency GNSS in view of phase scintillations. A connection between the possibility of improving the multifrequency GNSS accuracy and diffraction effects in radio signal propagation through the randomly inhomogeneous ionosphere is shown. The numerical simulation has revealed that the systematic, residual ionospheric error is considerably reduced when we pass on from dual-frequency to triple-frequency measurements. The change in the residual error variance during such a transition depends however on the relationship between the inner scale of the turbulent spectrum of ionospheric irregularities and the Fresnel radius. Given the inner scale larger than the Fresnel radius, not only the systematic error, but also the standard deviation reduces when we pass on from dual-frequency to triple-frequency measurements. Otherwise, when the Fresnel radius exceeds the inner scale, the variance increases with increasing number of frequencies in use. Numéro de notice : A2011-165 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0425-z Date de publication en ligne : 27/11/2010 En ligne : https://doi.org/10.1007/s00190-010-0425-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30943 [article]

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Innovations in individual feature history management: the significance of feature-based temporal model / J. Choi in Geoinformatica, vol 12 n° 1 (March - May 2008)  

Public [article]  inGeoinformatica > vol 12 n° 1 (March - May 2008) . - pp 1 - 20 Titre : Innovations in individual feature history management: the significance of feature-based temporal model Type de document : Article/Communication Auteurs : J. Choi, Auteur ; J. Seong, Auteur ; B. Kim, Auteur ; E. Lynn Usery, Auteur Année de publication : 2008 Article en page(s) : pp 1 - 20 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] couche thématique [Termes IGN] données multitemporelles [Termes IGN] historique des données [Termes IGN] modèle conceptuel de données localisées [Termes IGN] modèle conceptuel de données spatio-temporelles [Termes IGN] modèle relationnel [Termes IGN] SIG 4D Résumé : (Auteur) A feature relies on three dimensions (space, theme, and time) for its representation. Even though spatiotemporal models have been proposed, they have principally focused on the spatial changes of a feature. In this paper, a feature-based temporal model is proposed to represent the changes of both space and theme independently. The proposed model modifies the ISO’s temporal schema and adds new explicit temporal relationship structure that stores temporal topological relationship with the ISO’s temporal primitives of a feature in order to keep track feature history. The explicit temporal relationship can enhance query performance on feature history by removing topological comparison during query process. Further, a prototype system has been developed to test a proposed feature-based temporal model by querying land parcel history in Athens, Georgia. The result of temporal query on individual feature history shows the efficiency of the explicit temporal relationship structure. Copyright Springer Numéro de notice : A2008-067 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1007/s10707-007-0019-y En ligne : https://doi.org/10.1007/s10707-007-0019-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29062 [article]

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