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Map calcul in GIS: a proposal and demonstration / Muki M. Haklay in International journal of geographical information science IJGIS, vol 18 n° 2 (march 2004)

Public [article]  inInternational journal of geographical information science IJGIS > vol 18 n° 2 (march 2004) . - pp 107 - 125 Titre : Map calcul in GIS: a proposal and demonstration Type de document : Article/Communication Auteurs : Muki M. Haklay, Auteur Année de publication : 2004 Article en page(s) : pp 107 - 125 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes descripteurs IGN] cartographie numérique [Termes descripteurs IGN] couche thématique [Termes descripteurs IGN] fonction numérique [Termes descripteurs IGN] implémentation (informatique) [Termes descripteurs IGN] langage fonctionnel [Termes descripteurs IGN] système d'information géographique Résumé : (Auteur) This paper provides a new representation for fields (continuous surfaces) in Geographical Information Systems (GIS), based on the notion of spatial functions and their combinations. Following Tomlin's (1990) Map Algebra, the term 'Map Calculus' is used for this new representation. In Map Calculus, GIS layers are stored as functions, and new layers can be created by combinations of other functions. This paper explains the principles of Map Calculus and demonstrates the creation of functionbased layers and their supporting management mechanism. The proposal is based on Church's (1941) Lambda Calculus and elements of functional computer languages (such as Lisp or Scheme). Numéro de notice : A2004-038 Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26566 [article]

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Areas of fuzzy geographical entities / Cidália Costa Fonte in International journal of geographical information science IJGIS, vol 18 n° 2 (march 2004)

Public [article]  inInternational journal of geographical information science IJGIS > vol 18 n° 2 (march 2004) . - pp 127 - 150 Titre : Areas of fuzzy geographical entities Type de document : Article/Communication Auteurs : Cidália Costa Fonte, Auteur ; W. Weldon, Auteur Année de publication : 2004 Article en page(s) : pp 127 - 150 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes descripteurs IGN] base de données floues [Termes descripteurs IGN] cartographie automatique [Termes descripteurs IGN] classification floue [Termes descripteurs IGN] objet flou [Termes descripteurs IGN] sous ensemble flou [Termes descripteurs IGN] système d'information géographique Résumé : (Auteur) Fuzzy Geographical Entities (FGEs) refer in this paper to geographical entities with fuzzy spatial extent. The use of FGEs in geographical information systems requires the existence of operators capable of processing them. In this paper, our contribution to that field focuses on the computation of areas. Two methods are considered, one crisp due to Rosenfeld (1984), which has limited applicability, and the other fuzzy, which is a new approach. The new fuzzy area operator gives more information about the possible values of the area and enables the fuzziness in the spatial extent of the entity to be propagated to the area. Crisp and fuzzy areas have different meanings, and the use of one or the other depends not only on the purpose of the computation but also on the semantics of the membership functions. When the FGEs are represented by normal fuzzy sets, the fuzzy area operator generates fuzzy numbers, and therefore arithmetic operations can be performed with them using fuzzy arithmetic. However, we show that care must be taken with the use of the fuzzy arithmetic operators because, in some situations, the usual operators should not be applied. Properties of the Rosenfeld and fuzzy area operators are analysed, establishing a parallel with properties of the areas of crisp sets. Numéro de notice : A2004-039 Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26567 [article]

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Using quadtree segmentation to support error modelling in categorical raster data / S. De Bruin in International journal of geographical information science IJGIS, vol 18 n° 2 (march 2004)

Public [article]  inInternational journal of geographical information science IJGIS > vol 18 n° 2 (march 2004) . - pp 151 - 168 Titre : Using quadtree segmentation to support error modelling in categorical raster data Type de document : Article/Communication Auteurs : S. De Bruin, Auteur ; A.J. DE Wit, Auteur Année de publication : 2004 Article en page(s) : pp 151 - 168 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes descripteurs IGN] arbre quadratique [Termes descripteurs IGN] carte d'occupation du sol [Termes descripteurs IGN] données maillées [Termes descripteurs IGN] hétérogénéité [Termes descripteurs IGN] modèle d'erreur [Termes descripteurs IGN] précision de la classification [Termes descripteurs IGN] simulation [Termes descripteurs IGN] système d'information géographique [Termes descripteurs IGN] variogramme Résumé : (Auteur) This paper explores the use of quadtree segmentation of a land-cover map to improve error modelling by (1) accounting for variation in classification accuracy among differently sized homogeneous map regions and (2) improving the statistical properties of map realizations generated by sequential indicator simulation (SIS). The latter was accomplished by locating the first simulation nodes -which affect many subsequent local simulations- within the largest quadtree leaves. These represent the largest homogeneous and hypothetically most accurately classified areas on the map. A case study showed that, indeed, the overall accuracy of the land-cover map increased with the quadtree leaf size, ranging from 67% for single cells in heterogeneous areas to 98% for homogeneous blocks of 256 cells. A map of the prior probability of each land-cover class was prepared on the basis of quadtree level-specific confusion matrices. Next, two unconditional SIS algorithms were used to generate sets of 50 realizations of the map, thereby accounting for spatial continuity of the residuals between indicator-transformed reference data and the priors. The proposed quadtree-guided SIS outperformed the more common multiple-steps method as judged by the reproduction of target proportions of map categories, class-specific accuracy levels and variogram reproduction. Numéro de notice : A2004-040 Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26568 [article]

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Intra-urban location and clustering of road accidents using GIS: a Belgian example / T. Steenberghen in International journal of geographical information science IJGIS, vol 18 n° 2 (march 2004)

Public [article]  inInternational journal of geographical information science IJGIS > vol 18 n° 2 (march 2004) . - pp 169 - 181 Titre : Intra-urban location and clustering of road accidents using GIS: a Belgian example Type de document : Article/Communication Auteurs : T. Steenberghen, Auteur ; Isabelle Thomas, Auteur ; et al., Auteur Année de publication : 2004 Article en page(s) : pp 169 - 181 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes descripteurs IGN] accident de la route [Termes descripteurs IGN] agrégation [Termes descripteurs IGN] analyse comparative [Termes descripteurs IGN] analyse de groupement [Termes descripteurs IGN] base de données urbaines [Termes descripteurs IGN] Belgique [Termes descripteurs IGN] circulation urbaine [Termes descripteurs IGN] flux [Termes descripteurs IGN] géocodage [Termes descripteurs IGN] réseau routier [Termes descripteurs IGN] sécurité routière [Termes descripteurs IGN] segmentation dynamique [Termes descripteurs IGN] système d'information géographique [Termes descripteurs IGN] trafic routier [Termes descripteurs IGN] zone urbaine Résumé : (Auteur) This paper aims to show the usefulness of GIS and point pattern techniques for defining road-accident black zones within urban agglomerations. The location of road accidents is based on dynamic segmentation, address geocoding and intersection identification. One-dimensional (line) and two-dimensional (area) clustering techniques for road accidents are compared. Advantages and drawbacks are discussed in relation to network and traffic characteristics. Linear spatial clustering techniques appear to be better suited when traffic flows can be clearly identified along certain routes. For dense road networks with diffuse traffic patterns, two-dimensional techniques make it possible to identify accident-prone areas. The operationality of the techniques is illustrated by showing the impact of traffic-calming measures on the location and type of accidents in one Belgian town (Mechelen). Numéro de notice : A2004-041 Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26569 [article]

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A double continuous approach to visualization and analysis of categorial maps / T. Hengl in International journal of geographical information science IJGIS, vol 18 n° 2 (march 2004)

Public [article]  inInternational journal of geographical information science IJGIS > vol 18 n° 2 (march 2004) . - pp 183 - 202 Titre : A double continuous approach to visualization and analysis of categorial maps Type de document : Article/Communication Auteurs : T. Hengl, Auteur ; D.J.J. Walvoort, Auteur ; et al., Auteur Année de publication : 2004 Article en page(s) : pp 183 - 202 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes descripteurs IGN] analyse factorielle [Termes descripteurs IGN] carte thématique [Termes descripteurs IGN] classification barycentrique [Termes descripteurs IGN] classification floue [Termes descripteurs IGN] cohérence des couleurs [Termes descripteurs IGN] pixel [Termes descripteurs IGN] système d'information géographique [Termes descripteurs IGN] taxinomie [Termes descripteurs IGN] traitement d'image [Termes descripteurs IGN] transformation intensité-teinte-saturation [Termes descripteurs IGN] visualisation cartographique Résumé : (Auteur) A method to visualize multiple membership maps, called 'Colour mixture' (CM) is described and compared with alternative techniques: defuzzification and Pixel mixture. Six landform parameters were used to derive the landform classes using supervised fuzzy k-means classification. The continuous categorical map is derived by GIS calculations with colours, where colour values are considered to represent the taxonomic space spanned by the attribute variables. Coordinates of the nine class centres (landform facets) were first transformed from multivariate to two-dimensional attribute space using factor analysis, and then projected on the Hue Saturation Intensity (HSI) colourwheel. The taxonomic value was coded with the Hue and confusion with Saturation. To improve visual impression, saturation was replaced with whiteness. Classes that were closer in attribute space were merged into similar generic colours. The CM technique limits the derived mixed-colour map to seven generic hues independently of the total number of classes, which provides a basis for automated generalization. The confusion index derived from the mixed-colour map was used to derive primary boundaries and to locate areas of higher taxonomic confusion. Numéro de notice : A2004-042 Thématique : IMAGERIE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26570 [article]

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