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An empirical study of the effects of NLP components on Geographic IR performance / N. Stokes in International journal of geographical information science IJGIS, vol 22 n° 3 (march 2008)
[article]
Titre : An empirical study of the effects of NLP components on Geographic IR performance Type de document : Article/Communication Auteurs : N. Stokes, Auteur ; Y. Li, Auteur ; A. Moffat, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 247 - 264 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Infrastructure de données
[Termes IGN] accès aux données localisées
[Termes IGN] géomatique web
[Termes IGN] langage naturel (informatique)
[Termes IGN] recherche d'information géographique
[Termes IGN] résolution d'ambiguïté
[Termes IGN] toponymeRésumé : (Auteur) Natural language processing (NLP) techniques, such as toponym detection and resolution, are an integral part of most geographic information retrieval (GIR) architectures. Without these components, synonym detection, ambiguity resolution and accurate toponym expansion would not be possible. However, there are many important factors affecting the success of an NLP approach to GIR, including toponym detection errors, toponym resolution errors and query overloading. The aim of this paper is to determine how severe these errors are in state-of-the-art systems, and to what extent they affect GIR performance. We show that a careful choice of weighting schemes in the IR engine can minimize the negative impact of these errors on GIR accuracy. We provide empirical evidence from the GeoCLEF 2005 and 2006 datasets to support our observations. Numéro de notice : A2008-138 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810701626210 En ligne : https://doi.org/10.1080/13658810701626210 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29133
in International journal of geographical information science IJGIS > vol 22 n° 3 (march 2008) . - pp 247 - 264[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 079-08021 RAB Revue Centre de documentation En réserve L003 Disponible 079-08022 RAB Revue Centre de documentation En réserve L003 Disponible A comparison of illumination geometry-based methods for topographic correction of QuickBird images of an undulant area / J. Wu in ISPRS Journal of photogrammetry and remote sensing, vol 63 n° 2 (March - April 2008)
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Titre : A comparison of illumination geometry-based methods for topographic correction of QuickBird images of an undulant area Type de document : Article/Communication Auteurs : J. Wu, Auteur ; M. Bauer, Auteur ; D. Wang, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 223 - 236 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] analyse comparative
[Termes IGN] correction d'image
[Termes IGN] détail topographique
[Termes IGN] éclairement lumineux
[Termes IGN] exitance spectrale
[Termes IGN] image Quickbird
[Termes IGN] modèle numérique de surfaceRésumé : (Auteur) The high spatial resolution of QuickBird satellite images makes it possible to show spatial variability at fine details. However, the effect of topography-induced illumination variations become more evident, even in moderately sloped areas. Based on a high resolution (1 m) digital elevation model generated with high-frequency real-time kinematic global position system measurements, this study assessed topographic effects on QuickBird images of an undulant area (with a maximum slope of 7.4°) under different illumination and ground conditions. For land surfaces that were characterized by a non-Lambertian reflection, significant bidirectional variations in spectral radiances were found in all bands. The effectiveness of four illumination geometry-based topographic correction methods was evaluated. The results indicated that the empirical correction was the most effective method for all spectral bands in both solar and view directions, while the cosine correction gave the worst results. The C correction (in the solar direction) and the Minnaert correction reduced topographic effects, but not as effectively as the empirical correction. For the Lambertian, topographic effects were substantial only in the near infrared band in the solar direction. Bidirectional variations of spectral radiances in other bands and/or view directions were minimal and topographic corrections may not be necessary. None of these methods significantly changed the spatial variability of spectral radiances, although the histogram distributions were greatly modified by the cosine correction and the Minnaert correction. Copyright ISPRS Numéro de notice : A2008-116 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2007.08.004 En ligne : https://doi.org/10.1016/j.isprsjprs.2007.08.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29111
in ISPRS Journal of photogrammetry and remote sensing > vol 63 n° 2 (March - April 2008) . - pp 223 - 236[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 081-08021 SL Revue Centre de documentation Revues en salle Disponible Fast error analysis of continuous GPS observations / M. Bos in Journal of geodesy, vol 82 n° 3 (March 2008)
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Titre : Fast error analysis of continuous GPS observations Type de document : Article/Communication Auteurs : M. Bos, Auteur ; R. Fernandes, Auteur ; S. Williams, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 157 - 166 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] bruit blanc
[Termes IGN] classification par maximum de vraisemblance
[Termes IGN] données GPS
[Termes IGN] incertitude des données
[Termes IGN] série temporelleRésumé : (Auteur) It has been generally accepted that the noise in continuous GPS observations can be well described by a power-law plus white noise model. Using maximum likelihood estimation (MLE) the numerical values of the noise model can be estimated. Current methods require calculating the data covariance matrix and inverting it, which is a significant computational burden. Analysing 10 years of daily GPS solutions of a single station can take around 2 h on a regular computer such as a PC with an AMD AthlonTM 64 X2 dual core processor. When one analyses large networks with hundreds of stations or when one analyses hourly instead of daily solutions, the long computation times becomes a problem. In case the signal only contains power-law noise, the MLE computations can be simplified to a O(N log N) process where N is the number of observations. For the general case of power-law plus white noise, we present a modification of the MLE equations that allows us to reduce the number of computations within the algorithm from a cubic to a quadratic function of the number of observations when there are no data gaps. For time-series of three and eight years, this means in practise a reduction factor of around 35 and 84 in computation time without loss of accuracy. In addition, this modification removes the implicit assumption that there is no environment noise before the first observation. Finally, we present an analytical expression for the uncertainty of the estimated trend if the data only contains power-law noise. Copyright Springer Numéro de notice : A2008-167 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0165-x En ligne : https://doi.org/10.1007/s00190-007-0165-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29162
in Journal of geodesy > vol 82 n° 3 (March 2008) . - pp 157 - 166[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-08031 RAB Revue Centre de documentation En réserve L003 Disponible 266-08032 RAB Revue Centre de documentation En réserve L003 Disponible Geographic intention and modification in Web search / R. Jones in International journal of geographical information science IJGIS, vol 22 n° 3 (march 2008)
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Titre : Geographic intention and modification in Web search Type de document : Article/Communication Auteurs : R. Jones, Auteur ; W. Zhang, Auteur ; B. Rey, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : pp 229 - 246 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Infrastructure de données
[Termes IGN] données localisées
[Termes IGN] Etats-Unis
[Termes IGN] géomatique web
[Termes IGN] recherche d'information géographique
[Termes IGN] requête spatiale
[Termes IGN] toile d'araignée mondialeRésumé : (Auteur) Web searchers signal their geographic intent by using place-names in search queries. They also indicate their flexibility about geographic specificity by reformulating their queries. By examining this data we can learn to understand web searcher flexibility with respect to geographic intent. We examine aggregated data of queries with locations, and locations identified from IP addresses, to identify overall distance preferences, as well as distance preferences by search topic. We also examine query rewriting: both deliberate query rewriting, conducted in web search sessions, and automated query rewriting, with manual relevance judgments of geo-modified queries. We find geo-specification in 12.7% of user query rewrites in search sessions, and show the breakdown into sub-classes such as same-city, same-state, same-country and different-country. We also measure the dependence between US-state-name and distance-of-modified-location-from-original-location, finding that Vermont web searchers modify their locations greater distances than California web searchers. We find that automatically-modified queries are perceived as much more relevant when the geographic component is unchanged. We look at the relationship between the non-location part of a query and the distance from the user. We see that people search for child day-care near their locations and maps far from where they are located. We also give distance profiles for the top topics which cooccur with place-names in queries, which could be used to set document priors based on document proximity and query topic. Copyright Taylor & Francis Numéro de notice : A2008-137 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810701626186 En ligne : https://doi.org/10.1080/13658810701626186 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29132
in International journal of geographical information science IJGIS > vol 22 n° 3 (march 2008) . - pp 229 - 246[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 079-08021 RAB Revue Centre de documentation En réserve L003 Disponible 079-08022 RAB Revue Centre de documentation En réserve L003 Disponible
[article]
Titre : GNSS indoors : fighting the fading, part 1 Type de document : Article/Communication Auteurs : Günter W. Hein, Auteur ; M. Paonni, Auteur ; V. Kropp, Auteur ; et al., Auteur Année de publication : 2008 Article en page(s) : 10 p. ; pp 43 - 52 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] positionnement en intérieur
[Termes IGN] signal GNSS
[Termes IGN] traitement du signalRésumé : (Editeur) The ability to receive low-power GNSS signals inside buildings represents a veritable Holy Grail for product designers and manufacturers. Despite increases in receiver sensitivity and sophisticated signal-processing techniques, consistent and robust positioning indoors has not been achieved. In this first of a two-part exploration of the subject, the authors review existing models of indoor signal processing and the results of a new test designed to create an original model of satellite-navigation signal behavior as it propagates through diverse room shapes and building materials. Copyright Gibbons Media & Research LLC Numéro de notice : A2008-648 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33527
in Inside GNSS > vol 3 n° 2 (March 2008) . - 10 p. ; pp 43 - 52[article]Voir aussiDocuments numériques
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