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Assessing the performance of multi-GNSS precise point positioning in Asia-Pacific region / X. Zhao in Survey review, vol 49 n° 354 (September 2017)  

Public [article]  inSurvey review > vol 49 n° 354 (September 2017) . - pp 186 - 196 Titre : Assessing the performance of multi-GNSS precise point positioning in Asia-Pacific region Type de document : Article/Communication Auteurs : X. Zhao, Auteur ; S. Wang, Auteur ; C. Liu, Auteur ; J. Ou, Auteur ; X. Yu, Auteur Année de publication : 2017 Article en page(s) : pp 186 - 196 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] Asie (géographie politique) [Termes IGN] données BeiDou [Termes IGN] données GLONASS [Termes IGN] données GPS [Termes IGN] filtre de Kalman [Termes IGN] modèle stochastique [Termes IGN] Pacifique (océan) [Termes IGN] positionnement ponctuel précis [Termes IGN] test de performance Résumé : (Auteur) Multi-Global Navigation Satellite System (GNSS) integration can effectively improve the satellite geometry strength, and certain effect on the precise point positioning (PPP) accuracy and convergence speed. Taking the system difference into account, this paper deduces the unified GNSS observation model, which is extended to the multi-GNSS PPP functional model. Meanwhile, the stochastic model used in Kalman filter parameter estimation is presented in the paper. Furthermore, to evaluate the performance of the multi-GNSS PPP in Asia-Pacific region, observed data from the International GNSS Service reference stations are analysed using the self-developed software. In detail, the results from Global Positioning System (GPS)-, GLObal NAvigation Satellite System (GLONASS)- and BeiDou Navigation Satellite System (BDS)-only PPP, double combined PPP and GPS/GLONASS/BDS combined PPP under the different observation duration and cut-off elevation angles are analysed. Results demonstrate: (1) compared with the single system PPP, the convergence speed of the multi-GNSS PPP is improved while the accuracy is not significantly improved after processing the 24-h data set; (2) when the observation duration is short, such as 0.5 h, the mean convergence percentage of the BDS combined with GPS and GLONASS PPP increases by an average of 49.6% compared with the single individual systems except for BDS, respectively, under the cut-off angle of 5° and (3) when PPP positioning with high cut-off elevation angles, and at the point of centimetre-level positioning, the GPS/GLONASS/BDS combined PPP has a better performance on the convergence percentage and convergence speed. For example, the percentages of the position biases within 0–5 cm for GPS/GLONASS/BDS are increased by 7.2 and 4.5% in North and East direction compared with GPS/GLONASS under the cut-off angle of 35°, more than any other. And the mean convergence time is only 14.5 min. Numéro de notice : A2017-544 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1151576 En ligne : https://doi.org/10.1080/00396265.2016.1151576 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86599 [article]

An algorithm for the generation of Voronoi diagrams on the sphere based on QTM [quaternary triangular mesh] / Jun Chen in Photogrammetric Engineering & Remote Sensing, PERS, vol 69 n° 1 (January 2003)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 69 n° 1 (January 2003) . - pp 79 - 89 Titre : An algorithm for the generation of Voronoi diagrams on the sphere based on QTM [quaternary triangular mesh] Type de document : Article/Communication Auteurs : Jun Chen, Auteur ; X. Zhao, Auteur ; Z. Li, Auteur Année de publication : 2003 Article en page(s) : pp 79 - 89 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes IGN] diagramme de Voronoï [Termes IGN] maille triangulaire [Termes IGN] objet géographique linéaire [Termes IGN] objet géographique ponctuel [Termes IGN] objet géographique zonal [Termes IGN] sphère Résumé : (Auteur) In order to efficiently store and analyze spatial data on a global scale, the digital expression of Earth data in a data model must be global, continuous, and conjugate, i.e., a spherical dynamic data model is needed. The Voronoi data structure is the only published attempt (Wright and Goodchild, 1997) and the only possible solution currently available (Li et al., 1999) for a dynamic Gis. However, the complexity of the Voronoi algorithm for line sets and area sets in vector mode limits its application in a dynamic GIS. So far, there is no raster-based Voronoi algorithm for objects (including points, arcs, and regions) on a spherical surface. To overcome this serious deficiency, an algorithm for generating u spherical Voronoi diagram is presented, based on the O-QTM (Octahedral Quaternary Triangular Mesh). The principle of the dilation operation in mathematical morphology is extended to the spherical surface. A method is developed for a spherical distance transformation based on the QTM. A detailed algorithm is also presented. This algorithm can handle points, arcs, and area features on a spherical surface. Tests have shown that the computational time consumption of this algorithm with points, arcs, and areas is equal and proportionate to the levels of the spherical surface tessellation; and the difference (distortion) between the great circle distance and the QTm cells distance is slightly related to spherical distance (not as the roster dilation on a planar surface), and is mainly related to the locations of the generating points. Numéro de notice : A2003-004 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.14358/PERS.69.1.79 En ligne : https://doi.org/10.14358/PERS.69.1.79 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22302 [article]