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Spatio-temporal GIS design for exploring interactions of human activities / H. Yu in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 3 - 19 Titre : Spatio-temporal GIS design for exploring interactions of human activities Type de document : Article/Communication Auteurs : H. Yu, Auteur Année de publication : 2006 Article en page(s) : pp 3 - 19 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes IGN] analyse spatio-temporelle [Termes IGN] ArcGIS [Termes IGN] co-positionnement [Termes IGN] données spatiotemporelles [Termes IGN] géographie humaine [Termes IGN] interaction spatiale [Termes IGN] maladie infectieuse [Termes IGN] programmation informatique [Termes IGN] prototype [Termes IGN] réalité virtuelle [Termes IGN] sécurité [Termes IGN] segmentation dynamique [Termes IGN] système d'information géographique [Termes IGN] Time-geography Résumé : (Auteur) An effective representation of human activities in geographic information systems (GIS) presents a challenging research topic. Recent developments of information and communication technologies (ICT), which enable a virtual space and allow people to interact with others remotely, make such efforts even more difficult. This paper first extends the space-time path concept of Hägerstrand's time geography to represent both physical and virtual activities in a space-time context. A spatio-temporal GIS design which can accommodate the extended space-time path concept is proposed to support the exploration of spatio-temporal patterns of human interactions in physical and virtual spaces. Using time as a linear referencing system, a temporal dynamic segmentation method was developed to dynamically locate physical and virtual activities on space-time paths. The GIS design supports the identification of four different spatio-temporal patterns (i.e., co-existence, co-location in space, co-location in time, and no co-location in either space or time) of human interactions through their space-time paths. Using a hypothetical activity dataset, a prototype system is implemented as a three-dimensional GIS (i.e., two-dimensional space + one-dimensional time) in ArcGIS. The prototype system demonstrates the feasibility and potential of applying spatio-temporal GIS concepts to extend Hägerstrand's time-geographic framework for the representation and analysis of human interactions in both physical and virtual spaces. The proposed GIS design can be useful in such applications as understanding traffic congestion, tracking terrorist activities, and modeling the spread of infections diseases. Copyright CAGIS Numéro de notice : A2006-202 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1559/152304006777323136 En ligne : https://doi.org/10.1559/152304006777323136 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27929 [article]

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A uniform sky illumination model to enhance shading of terrain and urban areas / Patrick Kennelly in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 21 - 36 Titre : A uniform sky illumination model to enhance shading of terrain and urban areas Type de document : Article/Communication Auteurs : Patrick Kennelly, Auteur ; J. Stewart, Auteur Année de publication : 2006 Article en page(s) : pp 21 - 36 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie numérique [Termes IGN] correction des ombres [Termes IGN] éclairement lumineux [Termes IGN] estompage automatique [Termes IGN] Nevada (Etats-Unis) [Termes IGN] ombre [Termes IGN] représentation des détails topographiques [Termes IGN] système d'information géographique [Termes IGN] Texas (Etats-Unis) [Termes IGN] zone urbaine Résumé : (Auteur) Users of geographic information systems (GIS) usually render terrain using a point light source defined by an illumination vector. A terrain shaded from a single point provides good perceptual cues to surface orientation. This type of hill shading, however, does not include any visual cues to the relative height of surface elements. We propose shading the terrain under uniform diffuse illumination, where light arrives equally from all directions of a theoretical sky surrounding the terrain. Surface elements at lower elevations tend to have more of the sky obscured from view and are thus shaded darker. This tinting approach has the advantage that it provides more detailed renderings than point source illumination. We describe two techniques of computing terrain shading under uniform diffuse illumination. One technique uses a GIS-based hill-shading and shadowing tool to combine many point source renderings into one approximating the terrain under uniform diffuse illumination. The second technique uses a C++ computer algorithm for computing the inclination to the horizon in all azimuth directions at all points of the terrain. These virtual horizons are used to map sky brightness to the rendering of the terrain. To evaluate our techniques, we use two Digital Elevation Models (DEMs)-of the Schell Creek Range of eastern Nevada and a portion of downtown Houston, Texas, developed from Light Detection and Ranging (lidar) data. Renderings based on the uniform diffuse illumination model show more detailed changes in shading than renderings based on a point source illumination model. Copyright CaGISociety Numéro de notice : A2006-203 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1559/152304006777323118 En ligne : https://doi.org/10.1559/152304006777323118 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27930 [article]

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Conflict removal between B-spline curves for isobathymetric line generalization using a snake model / E. Guilbert in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 37 - 52 Titre : Conflict removal between B-spline curves for isobathymetric line generalization using a snake model Type de document : Article/Communication Auteurs : E. Guilbert, Auteur ; Eric Saux, Auteur ; Marc Daniel, Auteur Année de publication : 2006 Article en page(s) : pp 37 - 52 Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme snake [Termes IGN] B-Spline [Termes IGN] base de données bathymétriques [Termes IGN] bathymétrie [Termes IGN] cohérence des données [Termes IGN] conflit d'espace [Termes IGN] généralisation cartographique automatisée [Termes IGN] isobathe [Termes IGN] polyligne [Vedettes matières IGN] Généralisation Résumé : (Auteur) This paper describes a method for suppressing distance conflicts between isobathymetric lines modeled with B-spline curves for cartographic generalization. The initial B-spline curves are obtained by compressing a set of polygonal lines representing the raw data. The conflict removal is realized by respecting strong cartographic constraints, such as the navigation safety and the legibility of the map, and weak constraints, such as the preservation of the submarine relief. A polygonal line representing the minimal displacement that corrects a conflict is first computed. Then, the curve is deformed using a snake model. The constraints are expressed via different energy terms, and the curve is deformed until a valid solution is reached. In order to apply the method without user intervention, the shape parameters of the snake are set automatically. The advantage of the method is that it ensures the respect of strong constraints in every case while taking into account the weaker ones. The method can also be applied to the correction of visual self-intersections. The use of a snake model combined with B-spline curves permits a better control of the deformation than polygonal lines better preserving of the shape of the curves. Examples of real case studies issued from bathymetric databases are provided, and the benefits and drawbacks of the method are discussed. Copyright CaGISociety Numéro de notice : A2006-204 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1559/152304006777323145 En ligne : https://doi.org/10.1559/152304006777323145 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27931 [article]

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Placing text and icon labels simultaneously: a real-time method / Qian Zhang in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 53 - 64 Titre : Placing text and icon labels simultaneously: a real-time method Type de document : Article/Communication Auteurs : Qian Zhang, Auteur ; Lars Harrie, Auteur Année de publication : 2006 Article en page(s) : pp 53 - 64 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie numérique [Termes IGN] cartographie automatique [Termes IGN] conflit d'espace [Termes IGN] placement automatique des écritures [Termes IGN] placement automatique des signes conventionnels [Termes IGN] temps réel Résumé : (Auteur) This paper presents a method of combining text and icon label placement in a real-time computing environment. The method computes label configurations based on placement properties, cartographic disturbance, and label overlap. The process is divided into four phases. In the first phase, candidate positions of the text labels are chosen. In the second phase, the same is done for the icon labels. The choice of candidate positions is based on cartographic preference and cartographic disturbance. The removal of overlap between labels is solved, in the third phase, by means of a combinatorial optimization technique (simulated annealing). When there are label pairs in conflict that could not be resolved, the fourth and final step is executed to remove one label in the pair. The success of the proposed method lies in the ability to effectively reduce the search space for the combinatorial optimization. A number of strategies for reducing search space have been evaluated in a case study. The results show that a good search-space-reduction strategy will lead to acceptable solutions for text and icon labeling within a limited processing time. Copyright CaGISociety Numéro de notice : A2006-205 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1559/152304006777323127 En ligne : https://doi.org/10.1559/152304006777323127 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27932 [article]

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Shuttle Radar Topography Mission elevation data error and its relationship to land cover / A. Shortridge in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) Titre : Shuttle Radar Topography Mission elevation data error and its relationship to land cover Type de document : Article/Communication Auteurs : A. Shortridge, Auteur Année de publication : 2006 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] analyse comparative [Termes IGN] données altimétriques [Termes IGN] erreur systématique [Termes IGN] image radar moirée [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] MNS SRTM [Termes IGN] modèle numérique de surface [Termes IGN] modèle numérique de terrain [Termes IGN] occupation du sol [Termes IGN] précision altimétrique [Termes IGN] qualité des données Résumé : (Auteur) The Shuttle Radar Topography Mission (SRTM) has resulted in the construction of the first publicly available near-global high resolution digital elevation model (DEM). The utility of this DEM, as for any geospatial data set, is a function of its quality. This paper is concerned with the assessment of SRTM accuracy and its relationship to land cover. Two methods-one raster-based and one point-based-are compared to match "finished" three-arc-second SRTM data to high precision, high accuracy surveyed elevations, as well as a corresponding DEM from the USGS National Elevation Dataset (NED). Differences between the two methodologies were not found to be significant. Error for the study site is substantially less than the mission objective, but substantially more than that for the NED. Significant overestimation of actual elevations pervades the SRTM DEM, and the overestimation is significantly higher in forested areas. This systematic error has implications both for applications employing SRTM data and for research on elevation data error modeling. Copyright CaGISociety Numéro de notice : A2006-206 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1559/152304006777323172 En ligne : https://doi.org/10.1559/152304006777323172 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27933 [article]

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Evaluating decision support systems for PPGIS applications / G. Aggett in Cartography and Geographic Information Science, vol 33 n° 1 (January 2006)  

Public [article]  inCartography and Geographic Information Science > vol 33 n° 1 (January 2006) . - pp 77 - 92 Titre : Evaluating decision support systems for PPGIS applications Type de document : Article/Communication Auteurs : G. Aggett, Auteur ; C. Mccoll, Auteur Année de publication : 2006 Article en page(s) : pp 77 - 92 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes IGN] analyse comparative [Termes IGN] approche participative [Termes IGN] outil d'aide à la décision [Termes IGN] participation du public [Termes IGN] SIG participatif Résumé : (Auteur) A number of decision support systems (DSS) were evaluated prior to commencing public participatory geographic information systems (PPGIS) workshops within a small rural town undergoing rapid development. A paucity of existing information regarding the capabilities of these tools and their utility in supporting various PPGIS applications was noted. In order to, improve this situation and to better understand the strengths and limitations of the selected DSS Community Viz, we monitored and measured its utility in supporting community-based spatial decision-making processes from both a technologist and citizen's perspective. Results indicate that Community Viz has several strengths; however, the software exhibits some weaknesses in the context of our study. In assessing these results we realized that the utility of such findings could be much enhanced if contained within a structure that enables comparison between various DSS. Thus, a major objective was to develop and apply a DSS Evaluation Matrix (DSSEM) that can be used by PPGIS practitioners and participants to evaluate DSS in various project settings. The application of DSSEM will help formalize evaluations of DSS and encourage dissemination of results. Furthermore, it will assist practitioners, citizens, and agencies to make better choices when selecting DSS for PPGIS applications and provide DSS developers with the appropriate information to improve tool design. Copyright CaGISociety Numéro de notice : A2006-207 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1559/152304006777323163 En ligne : https://doi.org/10.1559/152304006777323163 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27934 [article]

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