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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]

Street-based topological representations and analyses for predicting traffic flow in GIS / Bin Jiang in International journal of geographical information science IJGIS, vol 23 n°9-10 (september 2009)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 23 n°9-10 (september 2009) . - pp 1119 - 1137 Titre : Street-based topological representations and analyses for predicting traffic flow in GIS Type de document : Article/Communication Auteurs : Bin Jiang, Auteur ; C. Liu, Auteur Année de publication : 2009 Article en page(s) : pp 1119 - 1137 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications SIG [Termes IGN] analyse spatiale [Termes IGN] axe médian [Termes IGN] découverte de connaissances [Termes IGN] Hong-Kong [Termes IGN] modèle de simulation [Termes IGN] relation topologique [Termes IGN] système d'information géographique [Termes IGN] trafic routier Résumé : (Auteur) It is well received in the space syntax community that traffic flow is significantly correlated to a morphological property of streets, which are represented by axial lines, forming a so called axial map. The correlation coefficient (R 2) approaches 0.8 and even a higher value according to the space syntax literature. In this paper, we study the same issue using the Hong Kong street network and the Hong Kong Annual Average Daily Traffic datasets, and find surprisingly that street-based topological representations (or street-street topologies) tend to be better representations than the axial map. In other words, vehicle flow is correlated to a morphological property of streets better than that of axial lines. Based on the finding, we suggest the street-based topological representations as an alternative GIS representation, and the topological analyses as a new analytical means for geographic knowledge discovery. Numéro de notice : A2009-382 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810701690448 En ligne : https://doi.org/10.1080/13658810701690448 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30012 [article]

Exemplaires(1)

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079-09061	RAB	Revue	Centre de documentation	En réserve L003	Disponible

A new application for PolSAR imagery in the field of moving target indication/ship detection / C. Liu in IEEE Transactions on geoscience and remote sensing, vol 45 n° 11 Tome 1 (November 2007)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 45 n° 11 Tome 1 (November 2007) . - pp 3426 - 3436 Titre : A new application for PolSAR imagery in the field of moving target indication/ship detection Type de document : Article/Communication Auteurs : C. Liu, Auteur ; H. Gierull, Auteur Année de publication : 2007 Article en page(s) : pp 3426 - 3436 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] données polarimétriques [Termes IGN] image radar moirée [Termes IGN] navire [Termes IGN] objet mobile [Termes IGN] polarimétrie radar Résumé : (Auteur) Recent analysis of a polarimetric synthetic aperture radar (PolSAR) velocity experiment has shown that azimuth ambiguities can provide useful information for the detection of moving targets with an across-track velocity component in PolSAR images using cross-polarization clutter cancellation. This paper examines this phenomenon using theoretical analysis and simulations and illustrates its application with experimental results. It is shown that, for reciprocal scatterers, the phase difference between HV and VH images is zero, whereas for HV and VH ambiguities, the phase difference is For land applications, clutter cancellation is essential for the detection of moving targets in PolSAR images. For maritime applications, it can be used to distinguish images from ambiguities. However, it is important to note that the underlying physical reasons for the performance of clutter cancellation are entirely different from ground moving target indication along-track interferometric SAR. It is also shown that cross-pol clutter cancellation is related to filtering of a double-rate-sampled single-channel SAR signal. Numéro de notice : A2007-503 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2007.907192 En ligne : https://doi.org/10.1109/TGRS.2007.907192 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28866 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-07111A	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Comparative assessment of the measures of thematic classification accuracy / C. Liu in Remote sensing of environment, vol 107 n° 4 (30/04/2007)  

Public [article]  inRemote sensing of environment > vol 107 n° 4 (30/04/2007) Titre : Comparative assessment of the measures of thematic classification accuracy Type de document : Article/Communication Auteurs : C. Liu, Auteur ; P. Frazier, Auteur ; L. Kumar, Auteur Année de publication : 2007 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] analyse comparative [Termes IGN] cartographie thématique [Termes IGN] classificateur [Termes IGN] coefficient de corrélation [Termes IGN] cohérence des données [Termes IGN] niveau d'analyse [Termes IGN] précision de la classification [Termes IGN] précision des données [Termes IGN] producteur [Termes IGN] utilisateur Résumé : (Auteur) Accuracy assessment of classified imagery is an important task in remote sensing. Various measures have been developed to describe and compare the accuracy of maps and the performance of different classifiers, but the extent to which these measures are consistent with each other is largely unknown. In this paper the consistency of fourteen category-level and twenty map-level accuracy measures was tested on 595 published error matrices using nonparametric correlation coefficients (Spearman's rho and Kendall's tau-b) as well as the probability of concordance. The results show that four groups can be identified for the category-level measures and three groups for map-level measures. The consistency among the measures within a group is generally higher than that among the measures from different groups though all the measures at the same level are highly consistent with each other. We recommend that user's accuracy and producer's accuracy and the overall accuracy should be provided as primary accuracy measures and the two relative entropy change measures and the mutual information normalized by the arithmetic mean of the entropies on map and ground truthing be provided as supplementary measures. The chance-corrected, error matrix-normalized and user's and producer's accuracy-combined measures were found to contain estimation and interpretation problems at both category- and map-levels and are therefore not recommended for general use. Copyright Elsevier Numéro de notice : A2007-158 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2006.10.010 En ligne : https://doi.org/10.1016/j.rse.2006.10.010 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28521 [article]