Geoinformatica . vol 7 n° 4Paru le : 01/12/2003 ISBN/ISSN/EAN : 1384-6175 |
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Ajouter le résultat dans votre panierEfficient flow computation on massive grid terrain datasets / L. Arge in Geoinformatica, vol 7 n° 4 (December 2003)
[article]
Titre : Efficient flow computation on massive grid terrain datasets Type de document : Article/Communication Auteurs : L. Arge, Auteur ; J.S. Chase, Auteur ; et al., Auteur Année de publication : 2003 Article en page(s) : pp 283 - 313 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Informatique
[Termes IGN] algorithmique
[Termes IGN] crue
[Termes IGN] données massives
[Termes IGN] écoulement des eaux
[Termes IGN] flux de données
[Termes IGN] géomorphologie
[Termes IGN] itinéraire
[Termes IGN] jeu de données localisées
[Termes IGN] mise à l'échelle
[Termes IGN] traitement de données localiséesRésumé : (Auteur) As detailed terrain data becomes available, GIS terrain applications target larger geographic areas at finer resolutions. Processing the massive datasets involved in such applications presents significant challenges to GIS systems and demands algorithms that are optimized for both data movement and computation. In this paper we present efficient algorithms for flow routing on massive grid terrain datasets, extending our previous work on flow accumulation. Our algorithms are developed in the framework of external memory algorithms and use I/0-techniques to achieve efficiency. We have implemented the algorithms in the Terraflow system, which is the first comprehensive terrain flow software system designed and optimized for massive data. We compare the performance of Terraflow with that of state-of-the-art commercial and opensource GIS systems. On large terrains, Terraflow outperforms existing systems by a factor of 2 to 1,000, and is capable of solving problems no system was previously able to solve. Numéro de notice : A2003-386 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1023/A:1025526421410 En ligne : https://doi.org/10.1023/A:1025526421410 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26466
in Geoinformatica > vol 7 n° 4 (December 2003) . - pp 283 - 313[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 057-03041 RAB Revue Centre de documentation En réserve L003 Disponible Polyline spatial join evaluation using raster approximation / L.G. Azevedo in Geoinformatica, vol 7 n° 4 (December 2003)
[article]
Titre : Polyline spatial join evaluation using raster approximation Type de document : Article/Communication Auteurs : L.G. Azevedo, Auteur ; R.S. Monteiro, Auteur ; et al., Auteur Année de publication : 2003 Article en page(s) : pp 315 - 336 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique
[Termes IGN] approximation
[Termes IGN] base de données localisées
[Termes IGN] filtre numérique
[Termes IGN] jointure spatiale
[Termes IGN] polyligne
[Termes IGN] requête spatialeRésumé : (Auteur) The main subject of spatial joins is polygons and polylines. Typical polygons and polylines can occupy several Kbytes. Since approximations use much less space, the processing of spatial joins can be greatly improved by the use of filters that reduce the need for examining the exact geometry of spatial objects in order to find the intersecting ones. Candidate pairs of approximations of spatial objects are evaluated using such filters. As a result, three possible sets of answers are identified: the positive one, composed of intersecting pairs; the negative one, composed of non-intersecting pairs; and the inconclusive one, composed of the remaining pairs of candidates. There are many approximations designed for polygons, but few are suitable for approximating polylines. This paper presents a spatial join processor based on the multi step query processor (MSQP) architecture [24]. We have developed a new polyfine approximation, named five color direction raster signature (5CDRS) [18]. It is used as the filter of MSQP's second step. The performance of the join processor and the approximation was evaluated with real world data sets. The results showed that our approach, when compared to others presented in the literature, reduced the inconclusive answers by 29% in the average. Consequently, the need for retrieving the representation of polylines and carrying out exact geometry tests is reduced by the same factor. As the exact geometry test is the most time consuming step, we have noticed that the overall time is also reduced by 38% in the average. The disk accesses are reduced by 41% in the average. Numéro de notice : A2003-387 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1025569305481 En ligne : https://doi.org/10.1023/A:1025569305481 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26467
in Geoinformatica > vol 7 n° 4 (December 2003) . - pp 315 - 336[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 057-03041 RAB Revue Centre de documentation En réserve L003 Disponible Performance evaluation of lazy deletion methods in R-trees / A. Nanopoulos in Geoinformatica, vol 7 n° 4 (December 2003)
[article]
Titre : Performance evaluation of lazy deletion methods in R-trees Type de document : Article/Communication Auteurs : A. Nanopoulos, Auteur ; M. Vassilakopoulos, Auteur ; Y. Manolopoulos, Auteur Année de publication : 2003 Article en page(s) : pp 337 - 354 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Information géographique
[Termes IGN] arbre-B
[Termes IGN] arbre-R
[Termes IGN] base de donnéesRésumé : (Auteur) Motivated by the way R-trees are implemented in commercial databases systems, in this paper we examine several deletion techniques for R-trees. In particular, in commercial systems R-tree entries are mapped onto relational tables, which implement their own concurrency protocols on top of existing table-level concurrency mechanisms, In analogy, the actual industrial implementations of B-trees do not apply the well-known merging procedure from textbooks in case of node underflows, but rather they apply the free-at-empty technique. This way, space is sacrificed for the benefit of faster deletions and less locking operations, whereas the search performance practically remains unaffected. In this context, we examine the efficiency of modifications to the original R-tree deletion algorithm, which relax certain constraints of this algorithm and perform a controlled reorganization procedure according to a specified criterion. We present the modified algorithms and experimental results about the impact of these modifications on the tree quality, the execution time for the deletion operation and the processing time of search queries, considering several parameters. The experimental results indicate that the modified algorithms improve the efficiency of the deletion operation, while they do not affect the quality of the R-tree and its performance with respect to search operations. Numéro de notice : A2003-388 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1025521422319 En ligne : https://doi.org/10.1023/A:1025521422319 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26468
in Geoinformatica > vol 7 n° 4 (December 2003) . - pp 337 - 354[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 057-03041 RAB Revue Centre de documentation En réserve L003 Disponible Bridging ontologies and conceptual schemas in geographic information integration / Frederico Fonseca in Geoinformatica, vol 7 n° 4 (December 2003)
[article]
Titre : Bridging ontologies and conceptual schemas in geographic information integration Type de document : Article/Communication Auteurs : Frederico Fonseca, Auteur ; C. Davis, Auteur ; G. Camara, Auteur Année de publication : 2003 Article en page(s) : pp 355 - 378 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Infrastructure de données
[Termes IGN] modèle conceptuel de données
[Termes IGN] modélisation
[Termes IGN] ontologie
[Termes IGN] schéma conceptuel de données
[Termes IGN] système d'information géographiqueRésumé : (Auteur) Integration of geographic information has increased in importance because of new possibilities arising from the interconnected world and the increasing availability of geographic information. Ontologies support the creation of conceptual models and help with information integration. In this paper, we propose a way to link the formal representation of semantics (i.e., ontotogies) to conceptual schemas describing information stored in databases. The main result is a formal framework that explains a mapping between a spatial ontology and a geographic conceptual schema. The mapping of ontologies to conceptual schemas is made using three different levels of abstraction: formal, domain, and application levels. At the formal level, highly abstract concepts are used to express the schema and the ontologies. At the domain level, the schema is regarded as an instance of a generic data model. At the application level, we focus on the particular case of geographic applications. We also discuss the influence of ontologies in both the traditional and geographic systems development methodologies, with an emphasis on the conceptual design phase. Numéro de notice : A2003-389 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1025573406389 En ligne : https://doi.org/10.1023/A:1025573406389 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26469
in Geoinformatica > vol 7 n° 4 (December 2003) . - pp 355 - 378[article]Réservation
Réserver ce documentExemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 057-03041 RAB Revue Centre de documentation En réserve L003 Disponible