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Efficiently computing the drainage network on massive terrains using external memory flooding process / Thiago L. Gomes in Geoinformatica, vol 19 n° 4 (October - December 2015)  

Public [article]  inGeoinformatica > vol 19 n° 4 (October - December 2015) . - pp 671 - 692 Titre : Efficiently computing the drainage network on massive terrains using external memory flooding process Type de document : Article/Communication Auteurs : Thiago L. Gomes, Auteur ; Salles V. G. Magalhães, Auteur ; Marcus V. A. Andrade, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 671 - 692 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] écoulement des eaux [Termes IGN] hydrologie [Termes IGN] modèle numérique de terrain [Termes IGN] réseau d'irrigation [Termes IGN] système d'information géographique Résumé : (auteur) We present EMFlow, a very efficient algorithm and its implementation, to compute the drainage network (i.e. the flow direction and flow accumulation) on huge terrains stored in external memory. Its utility lies in processing the large volume of high resolution terrestrial data newly available, which internal memory algorithms cannot handle efficiently. The flow direction is computed using an adaptation of our previous method RWFlood that uses a flooding process to quickly remove internal depressions or basins. Flooding, proceeding inward from the outside of the terrain, works oppositely to the common method of computing downhill flow from the peaks. To reduce the number of I/O operations, EMFlow adopts a new strategy to subdivide the terrain into islands that are processed separately. The terrain cells are grouped into blocks that are stored in a special data structure managed as a cache memory. EMFlow’s execution time was compared against the two most recent and most efficient published methods: TerraFlow and r.watershed.seg. It was, on average, 25 and 110 times faster than TerraFlow and r.watershed.seg respectively. Also, EMFlow could process larger datasets. Processing a 50000 × 50000 terrain on a machine with 2GB of internal memory took about 4500 seconds, compared to 87000 seconds for TerraFlow while r.watershed.seg failed on terrains larger than 15000 ×15000. On very small, say1000 ×1000 terrains, EMFlow takes under a second, compared to 6 and 20 seconds in r.watershed.seg and TerraFlow respectively. So EMFlow could be a component of a future interactive system where a user could modify terrain and immediately see the new hydrography. Numéro de notice : A2015--034 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1007/s10707-015-0225-y En ligne : https://doi.org/10.1007/s10707-015-0225-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81120 [article]

Planning unobstructed paths in traffic-aware spatial networks / Shuo Shang in Geoinformatica, vol 19 n° 4 (October - December 2015)  

Public [article]  inGeoinformatica > vol 19 n° 4 (October - December 2015) . - pp 723 - 746 Titre : Planning unobstructed paths in traffic-aware spatial networks Type de document : Article/Communication Auteurs : Shuo Shang, Auteur ; Jianjun Liu, Auteur ; Kai Zheng, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 723 - 746 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] accessibilité [Termes IGN] calcul d'itinéraire [Termes IGN] gestion des itinéraires [Termes IGN] itinéraire [Termes IGN] objet mobile [Termes IGN] trafic routier [Termes IGN] vitesse Mots-clés libres : traffic-aware spatial network Résumé : (auteur) Route planning and recommendation have received significant attention in recent years. In this light, we study a novel problem of planning unobstructed paths in traffic-aware spatial networks (TAUP queries) to avoid potential traffic congestions. We propose two probabilistic TAUP queries: (1) a time-threshold query like “what is the path from the check-in desk to the flight SK 1217 with the minimum congestion probability to take at most 45 minutes?”, and (2) a probability-threshold query like “what is the fastest path from the check-in desk to the flight SK 1217 whose congestion probability is less than 20 %?”. These queries are mainly motivated by indoor space applications, but are also applicable in outdoor spaces. We believe that these queries are useful in some popular applications, such as planning unobstructed paths for VIP bags in airports and planning convenient routes for travelers. The TAUP queries are challenged by two difficulties: (1) how to model the traffic awareness in spatial networks practically, and (2) how to compute the TAUP queries efficiently under different query settings. To overcome these challenges, we construct a traffic-aware spatial network G t a (V, E) by analyzing uncertain trajectories of moving objects. Based on G t a (V, E), two efficient algorithms are developed to compute the TAUP queries. The performances of TAUP queries are verified by extensive experiments on real and synthetic spatial data. Numéro de notice : A2015--035 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1007/s10707-015-0227-9 Date de publication en ligne : 10/04/2015 En ligne : http://dx.doi.org/10.1007/s10707-015-0227-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81121 [article]

From GPS and virtual globes to spatial computing - 2020 / Shashi Shekhar in Geoinformatica, vol 19 n° 4 (October - December 2015)  

Public [article]  inGeoinformatica > vol 19 n° 4 (October - December 2015) . - pp 799 - 832 Titre : From GPS and virtual globes to spatial computing - 2020 Type de document : Article/Communication Auteurs : Shashi Shekhar, Auteur ; Steven Feiner, Auteur ; Walid G. Aref, Auteur Année de publication : 2015 Article en page(s) : pp 799 - 832 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] données localisées [Termes IGN] évolution technologique [Termes IGN] géovisualisation [Termes IGN] information géographique numérique [Termes IGN] navigation [Termes IGN] positionnement par GPS [Termes IGN] prospective Résumé : (auteur) Spatial computing is a set of ideas, solutions, tools, technologies, and systems that transform our lives with a new prospect of understanding, navigating, visualizing and using locations. In this community whitepaper, we present a perspective on the changing world of spatial computing, research challenges and opportunities and geoprivacy issues for spatial computing. First, this paper provides an overview of the changing world of spatial computing. Next, promising technologies that resulted from the integration of spatial computing in the everyday lives of people is discussed. This integration results with promising technologies, research challenges and opportunities and geoprivacy issues that must be addressed to achieve the potential of spatial computing. Numéro de notice : A2015--036 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1007/s10707-015-0235-9 En ligne : http://dx.doi.org/10.1007/s10707-015-0235-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81122 [article]