Centre de documentation
scientifique

Dépouillements

Search algorithms for multiway spatial joins / Dimitris Papadias in International journal of geographical information science IJGIS, vol 16 n° 7 (october 2002)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 16 n° 7 (october 2002) . - pp 613 - 639 Titre : Search algorithms for multiway spatial joins Type de document : Article/Communication Auteurs : Dimitris Papadias, Auteur ; D. Arkoumanis, Auteur Année de publication : 2002 Article en page(s) : pp 613 - 639 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] arbre-R [Termes IGN] jointure spatiale [Termes IGN] recherche heuristique [Termes IGN] requête spatiale [Termes IGN] temps réel Résumé : (Auteur) This paper deals with multiway spatial joins when (i) there is limited time for query processing and the goal is to retrieve the best possible solutions within this limit (ii) there is unlimited time and the goal is to retrieve a single exact solution, if such a solution exists, or the best approximate one otherwise. The first case is motivated by the high cost of join processing in real-time systems involving large amounts of multimedia data, while the second one is motivated by applications that require 'negative' examples. We propose several search algorithms for query processing under theses conditions. For the limited-time case we develop some non-deterministic search heuristics that can quickly retrieve good solutions. However, these heuristics are not guaranteed to find the best solutions, even without a time limit. Therefore, for the unfirnited-time case we describe systematic search algorithms tailored specifically for the efficient retrieval of a single solution. Both types of algorithms are integrated with R-trees in order to prune the search space. Our proposal is evaluated with extensive experimental comparison. Numéro de notice : A2002-209 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1080/13658810210138733 En ligne : https://doi.org/10.1080/13658810210138733 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22124 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-02071	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Towards an evaluation of quality for names placement methods / S. Van Dijk in International journal of geographical information science IJGIS, vol 16 n° 7 (october 2002)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 16 n° 7 (october 2002) . - pp 641 - 661 Titre : Towards an evaluation of quality for names placement methods Type de document : Article/Communication Auteurs : S. Van Dijk, Auteur ; Marc Van Kreveld, Auteur ; Tycho Wiljan Strijk, Auteur ; A. Wolff, Auteur Année de publication : 2002 Article en page(s) : pp 641 - 661 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie numérique [Termes IGN] contrôle qualité [Termes IGN] indicateur de qualité [Termes IGN] placement automatique des écritures Résumé : (Auteur) The cartographic labelling problem is the problem of placing text on a map. This includes the positioning of the labels, and determining the shape in the case of line and area feature labels. There are many rules and customs that describe aspects of good label placement, like readability and clear association. This paper gives a classification of most label placement rules, and formalizes them into a function that can serve as a quality measure for label placement. If such a function is implemented, it allows comparison of the output of different label placement programs. We give a simple and a more refined example of the quality function. Numéro de notice : A2002-210 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810210138742 En ligne : https://doi.org/10.1080/13658810210138742 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22125 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-02071	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Data quality and model complexity for regional scale soil erosion prediction / A.J. Van Rompaey in International journal of geographical information science IJGIS, vol 16 n° 7 (october 2002)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 16 n° 7 (october 2002) . - pp 663 - 680 Titre : Data quality and model complexity for regional scale soil erosion prediction Type de document : Article/Communication Auteurs : A.J. Van Rompaey, Auteur ; G. Govers, Auteur Année de publication : 2002 Article en page(s) : pp 663 - 680 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] bassin hydrographique [Termes IGN] complexité [Termes IGN] érosion [Termes IGN] modèle mathématique [Termes IGN] qualité des données Résumé : (Auteur) Many spatially distributed environmental models have been developed for small spatial units (e.g. individual plots or fields). Their application at a regional scale (e.g. large drainage basins) was hitherto not very successful since most models are 'scale-specific'. In most cases the lack of input data is a limiting factor for an appropriate model application at a regional scale. The use of simplified models on the other hand, can only be successful if they have the appropriate degree of complexity. This leads to the following paradox: on the one hand a model should be based on process knowledge so that it will react correctly to changes imposed by the modelling system. Including all available process knowledge, however, will lead to an overparametrisation. The error propagation involved in the poor data quality can then deteriorate dramatically the accuracy of the output results. For optimal model predictions at a regional scale the model complexity has to be in balance with the quality of the available input data. The error involved in a model application can be split in two parts: on the one hand the intrinsic model error because of an incomplete description of the processes and on the other hand the input error because of the use of low quality data. The total error is the sum of both parts. A simplification of the modelling structure will lead to an increase of the intrinsic model error and a decrease of the input error. If observed field values are available they can be used to determine which model structure gives the best results, given the available data. In many cases such validation data are not available. However, also in these cases, a model user should be able to select an optimal model structure. In this paper a technique is presented that allows the determination of the optimal degree of model complexity for an application at a regional scale if no observed field data are available. If the uncertainty of a model parameter exceeds a certain threshold, the model structure must be further simplified by replacement of this parameter by an aggregated value or a constant. The use of the technique is illustrated via the application of a soil erosion model. Numéro de notice : A2002-211 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1080/13658810210148561 En ligne : https://doi.org/10.1080/13658810210148561 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22126 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-02071	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Using GIS in passive microwave soil moisture mapping and geostatistical analysis / A. Oldak in International journal of geographical information science IJGIS, vol 16 n° 7 (october 2002)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 16 n° 7 (october 2002) . - pp 681 - 698 Titre : Using GIS in passive microwave soil moisture mapping and geostatistical analysis Type de document : Article/Communication Auteurs : A. Oldak, Auteur ; Thomas J. Jackson, Auteur ; Y. Pachepsky, Auteur Année de publication : 2002 Article en page(s) : pp 681 - 698 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications SIG [Termes IGN] analyse de données [Termes IGN] analyse spatiale [Termes IGN] carte thématique [Termes IGN] Electronically Scanned Thinned Array Radiometer [Termes IGN] humidité du sol [Termes IGN] système d'information géographique [Termes IGN] télédétection en hyperfréquence Résumé : (Auteur) Soil moisture is an important hydrologic variable in both natural and agricultural ecosystems. Recent experiments, based on remote sensing data, provided observations of soil moisture distributions at a regional scale. One of the instruments is the Electronically Scanned Thinned Array Radiometer (ESTAR). Deployed on the aircraft, it measures brightness temperature (with the spatial resolution about 400m) that can be converted into estimates of volumetric soil moisture. The soil moisture retrieval algorithm requires additional data layers (like soil physical temperature, land cover, and soil texture) that come from different sources and have to be combined together in a uniform GIS. The objective of this paper is to report results of the GIS use to map soil surface moisture from passive microwave measurements and to quantify spatial structure of soil moisture distributions. The data were collected across a 10.000km area in Oklahoma during June and July 1997. The precipitation data and ground measurements from the test sites were also incorporated into GIS. The GIS data layers enable soil moisture distribution analysis with geostatistical tools. Semivariograms of soil moisture were nested and showed the presence of two scales. Rainfall was the dominant factor influencing soil moisture distribution at the regional scale, whereas soil texture was important at the local scale. Information about soil moisture, obtained with remote sensing techniques over space and time, and organized in a GIS with complementary environmental data layers, can be used in landscape pattern analysis, landscape models, land use assessment and management. Numéro de notice : A2002-212 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810210149407 En ligne : https://doi.org/10.1080/13658810210149407 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22127 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-02071	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Quantitative measures for spatial information of maps / Z. Li in International journal of geographical information science IJGIS, vol 16 n° 7 (october 2002)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 16 n° 7 (october 2002) . - pp 699 - 709 Titre : Quantitative measures for spatial information of maps Type de document : Article/Communication Auteurs : Z. Li, Auteur ; P. Huang, Auteur Année de publication : 2002 Article en page(s) : pp 699 - 709 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie [Termes IGN] distribution spatiale [Termes IGN] graphe [Termes IGN] indicateur de qualité [Termes IGN] information cartographique Résumé : (Auteur) The map is a medium for recording geographical information. The information contents of a map are of interest to spatial information scientists. In this paper, existing quantitative measures for map information are evaluated. It is pointed out that these are only measures for statistical information and some sort of topological information. However, these measures have not taken into consideration the spaces occupied by map symbols and the spatial distribution of these symbols. As a result, a set of new quantitative measures is proposed, for metric information, topological information and thematic information. An experimental evaluation is also conducted. Results show that the metric information is more meaningful than statistical information, and the new index for topological information is more meaningful than the existing one. It is also found that the new measure for thematic information is useful in practice. Numéro de notice : A2002-213 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810210149416 En ligne : https://doi.org/10.1080/13658810210149416 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22128 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-02071	RAB	Revue	Centre de documentation	En réserve L003	Disponible