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A bright idea: testing the feasibility of positionning using ambient light / J. Liu in GPS world, vol 25 n° 11 (novembre 2014)  

Public [article]  inGPS world > vol 25 n° 11 (novembre 2014) . - pp 45 - 50 Titre : A bright idea: testing the feasibility of positionning using ambient light Type de document : Article/Communication Auteurs : J. Liu, Auteur ; R. Chen, Auteur ; Y. Chen, Auteur ; et al., Auteur Année de publication : 2014 Article en page(s) : pp 45 - 50 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] éclairage [Termes IGN] positionnement en intérieur Index. décimale : 30.70 Navigation et positionnement Résumé : (Editeur) In this month colmumn, we take a look at simple, innovative method of light fingerprinting: the use of observations of the artificial light emitted by unmodified light fixtures as well as the natural light passes through windows and doorways in a technique for position determination inside buildings. Numéro de notice : A2014-613 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans En ligne : http://gpsworld.com/innovation-a-bright-idea/ Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74879 [article]

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Total least squares adjustment in partial errors-in-variables models: algorithm and statistical analysis / P. Xu in Journal of geodesy, vol 86 n° 8 (August 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 8 (August 2012) . - pp 661 - 675 Titre : Total least squares adjustment in partial errors-in-variables models: algorithm and statistical analysis Type de document : Article/Communication Auteurs : P. Xu, Auteur ; J. Liu, Auteur ; C. Shi, Auteur Année de publication : 2012 Article en page(s) : pp 661 - 675 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse de variance [Termes IGN] compensation non linéaire [Termes IGN] compensation par moindres carrés [Termes IGN] modèle d'erreur [Termes IGN] résidu [Termes IGN] traitement de données GNSS Résumé : (Auteur) The weighted total least squares (TLS) method has been developed to deal with observation equations, which are functions of both unknown parameters of interest and other measured data contaminated with random errors. Such an observation model is well known as an errors-in-variables (EIV) model and almost always solved as a nonlinear equality-constrained adjustment problem. We reformulate it as a nonlinear adjustment model without constraints and further extend it to a partial EIV model, in which not all the elements of the design matrix are random. As a result, the total number of unknowns in the normal equations has been significantly reduced. We derive a set of formulae for algorithmic implementation to numerically estimate the unknown model parameters. Since little statistical results about the TLS estimator in the case of finite samples are available, we investigate the statistical consequences of nonlinearity on the nonlinear TLS estimate, including the first order approximation of accuracy, nonlinear confidence region and bias of the nonlinear TLS estimate, and use the bias-corrected residuals to estimate the variance of unit weight. Numéro de notice : A2012-378 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0552-9 Date de publication en ligne : 23/03/2012 En ligne : https://doi.org/10.1007/s00190-012-0552-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31824 [article]

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Taiwanese Lidar project / J. Liu in GIM international, vol 25 n° 8 (August 2011)

Public [article]  inGIM international > vol 25 n° 8 (August 2011) . - pp 23 - 25 Titre : Taiwanese Lidar project Type de document : Article/Communication Auteurs : J. Liu, Auteur ; L. Fei, Auteur Année de publication : 2011 Article en page(s) : pp 23 - 25 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] données lidar [Termes IGN] grande échelle [Termes IGN] image aérienne [Termes IGN] orthophotoplan numérique [Termes IGN] risque naturel [Termes IGN] Taïwan [Termes IGN] télémétrie laser aéroporté Résumé : (Auteur) Nearly three-quarters of the territory of Taiwan and 95% of its population are exposed to frequent hazard. In the aftermath of typhoon Morakot that scourged Southern Taiwan on 8th and 9th august 2009, causing the worst flooding in a century, the authorities realized that the country was dreadfully lacking in detailed, accurate and current elevation data, as well as aerial imagery covering the entire territory (36 000 km2). In response, a national mapping program spanning 2010 to 2015 was launched with the aim of simultaneously capturing the entire country airborne Lidar and digital imagery. The authors discuss specifications, status and challenges posed by this large-scale, long-term project. Numéro de notice : A2011-335 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31114 [article]

Ionospheric effects on SAR imaging: a numerical study / J. Liu in IEEE Transactions on geoscience and remote sensing, vol 41 n° 5 (May 2003)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 41 n° 5 (May 2003) . - pp 939 - 947 Titre : Ionospheric effects on SAR imaging: a numerical study Type de document : Article/Communication Auteurs : J. Liu, Auteur ; Y. Kuga, Auteur ; et al., Auteur Année de publication : 2003 Article en page(s) : pp 939 - 947 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] correction ionosphérique [Termes IGN] dégradation d'image [Termes IGN] image radar moirée [Termes IGN] propagation ionosphérique Résumé : (Auteur) There has been an increasing interest in the use of spaceborne very high frequency ultra high frequency (VHFUHF) synthetic aperture radar (SAR) for measuring forest biomass and for detecting underground facilities. The propagation characseristics of the lowfrequency electromagnetic wave are severely affected by the ionosphere. Recently, Faraday rotation effects and SAR image degradation have been studied using an analytical model and a homogeneous ionosphere. In this paper, a numerical model is developed to investigate the SAR image degradation caused by an inhomogeneous ionosphere. Both horizontal and a vertical structures of the ionosphere are considered in this model. Three different cases are studied. The first is a vertically homogemous ionosphere, where the simulation condition is the same as in the analytical study by Ishimaru and others. The second is a vertical profile, which is introduced using the Chapman formula. The raybending effect is added for the ionosphere with a layered structure. Finally, both the vertical profile in electron density and the horizontal gradient in total electron content are considered b the simulation. Simulation results show good agreement with the theoretical analysis under the same conditions of the ionosphere. When both horizontal and vertical structures and the inhomogeneity of the ionosphere are considered in the model, the simulation result shows further image degradation and shift caused by the raybending effect. The simulation results also show the strong frequency dependence of the SAR image resolution. Numéro de notice : A2003-203 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2003.811813 En ligne : https://doi.org/10.1109/TGRS.2003.811813 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22499 [article]

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