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Automatic extraction of road markings from mobile Lidar point clouds / B. Yang in Photogrammetric Engineering & Remote Sensing, PERS, vol 78 n° 4 (April 2012)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 78 n° 4 (April 2012) . - pp 331 - 338 Titre : Automatic extraction of road markings from mobile Lidar point clouds Type de document : Article/Communication Auteurs : B. Yang, Auteur ; Leyuan Fang, Auteur ; Qi Li, Auteur ; et al., Auteur Année de publication : 2012 Article en page(s) : pp 331 - 338 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] extraction automatique [Termes IGN] interpolation [Termes IGN] lasergrammétrie [Termes IGN] segmentation [Termes IGN] semis de points [Termes IGN] signalisation routière Résumé : (Auteur) Among implicit information of laser points, the strength of reflection of laser points is closely related to the property of road materials which helps detecting road markings. This paper presents a novel approach to automatically extracting road markings from mobile lidar point clouds. An interpolation method is first used to generate a georeferenced feature image of the point cloud, which helps to isolate the points of road surfaces. Then, an algorithm is used to separate these points within a range according to their strength of reflection. The separated points are further segmented to remove non-road points based on height threshold. Finally, the outlines of road markings are extracted from the segmented points using the semantic knowledge of road markings. The results demonstrated that our method was very promising for automatic extraction of road markings from lidar point clouds collected by a land-based mobile lidar system, an Optech Lynx Mobile Mapper. Numéro de notice : A2012-178 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.78.4.331 En ligne : https://doi.org/10.14358/PERS.78.4.331 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31625 [article]

Algorithms for constrained k-nearest neighbor queries over moving object trajectories / Yunjun Gao in Geoinformatica, vol 14 n° 2 (April 2010)  

Public [article]  inGeoinformatica > vol 14 n° 2 (April 2010) . - pp 241 - 276 Titre : Algorithms for constrained k-nearest neighbor queries over moving object trajectories Type de document : Article/Communication Auteurs : Yunjun Gao, Auteur ; B. Zheng, Auteur ; G. Chen, Auteur ; Qi Li, Auteur Année de publication : 2010 Article en page(s) : pp 241 - 276 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] arbre-R [Termes IGN] base de données d'objets mobiles [Termes IGN] base de données spatiotemporelles [Termes IGN] classification barycentrique [Termes IGN] objet mobile [Termes IGN] processus spatial [Termes IGN] programmation par contraintes [Termes IGN] requête spatiale Résumé : (Auteur) An important query for spatio-temporal databases is to find nearest trajectories of moving objects. Existing work on this topic focuses on the closest trajectories in the whole data space. In this paper, we introduce and solve constrained k-nearest neighbor (CkNN) queries and historical continuous CkNN (HCCkNN) queries on R-tree-like structures storing historical information about moving object trajectories. Given a trajectory set D, a query object (point or trajectory) q, a temporal extent T, and a constrained region CR, (i) a CkNN query over trajectories retrieves from D within T, the k (? 1) trajectories that lie closest to q and intersect (or are enclosed by) CR; and (ii) an HCCkNN query on trajectories retrieves the constrained k nearest neighbors (CkNNs) of q at any time instance of T. We propose a suite of algorithms for processing CkNN queries and HCCkNN queries respectively, with different properties and advantages. In particular, we thoroughly investigate two types of CkNN queries, i.e., CkNNP and CkNNT, which are defined with respect to stationary query points and moving query trajectories, respectively; and two types of HCCkNN queries, namely, HCCkNNP and HCCkNNT, which are continuous counterparts of CkNNP and CkNNT, respectively. Our methods utilize an existing data-partitioning index for trajectory data (i.e., TB-tree) to achieve low I/O and CPU cost. Extensive experiments with both real and synthetic datasets demonstrate the performance of the proposed algorithms in terms of efficiency and scalability. Copyright Springer Numéro de notice : A2010-067 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1007/s10707-009-0084-5 Date de publication en ligne : 28/04/2009 En ligne : https://doi.org/10.1007/s10707-009-0084-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30263 [article]

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Vector moving gravimetry processing using implicit least squares / Qi Li (2010) 

Public Titre : Vector moving gravimetry processing using implicit least squares Type de document : Article/Communication Auteurs : Qi Li, Auteur ; Bertrand de Saint-Jean , Auteur ; Jérome Verdun , Auteur ; José Cali, Auteur ; Michel Diament , Auteur Editeur : Saint-Mandé : Institut Géographique National - IGN (2008-2011) Année de publication : 2010 Conférence : TG-SMM 2010, 2nd IAG symposium on terrestrial gravimetry : static and mobile measurements 22/06/2010 25/06/2010 Saint-Petersbourg Russie Langues : Anglais (eng) Numéro de notice : C2010-063 Affiliation des auteurs : LAREG+Ext (1991-2011) Nature : Poster nature-HAL : Poster-avec-CL DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102014

Documents numériques

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An integrated TIN and Grid method for constructing multi-resolution digital terrain models / B. Yang in International journal of geographical information science IJGIS, vol 19 n° 10 (november 2005)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 19 n° 10 (november 2005) . - pp 1019 - 1038 Titre : An integrated TIN and Grid method for constructing multi-resolution digital terrain models Type de document : Article/Communication Auteurs : B. Yang, Auteur ; Wei Shi, Auteur ; Qi Li, Auteur Année de publication : 2005 Article en page(s) : pp 1019 - 1038 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Information géographique [Termes IGN] analyse multirésolution [Termes IGN] modèle numérique de terrain [Termes IGN] système d'information géographique [Termes IGN] tessellation [Termes IGN] Triangulated Irregular Network [Termes IGN] visualisation 3D Résumé : (Auteur) Multi-resolution terrain models are an efficient approach to improve the speed of three dimensional (3D) visualizations, especially for terrain visualization in Geographical Information Systems (GIS). As a further development to existing algorithms and models, a new model is proposed for the construction of multiresolution terrain models in a 3D GIS. The new model represents multi-resolution terrains using two major methods for terrain representation: Triangulated Irregular Network (TIN) and regular grid (Grid). In this paper, first, the concepts and formal definitions of the new model are presented. Second, the methodology for constructing multi-resolution terrain models based on the new model is proposed. Third, the error of multi-resolution terrain models is analysed, and a set of rules is proposed to retain the important features (e.g. boundaries of man-made objects) within the multi-resolution terrain models. Finally, several experiments are undertaken to test the performance of the new model. The experimental results demonstrate that the new model can be applied to construct multi-resolution terrain models with good performance in terms of time cost and maintenance of the important features. Furthermore, a comparison with previous algorithms/models shows that the speed of rendering for 3D walking/flying through has been greatly improved by applying the new model. Numéro de notice : A2005-497 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810500391156 En ligne : https://doi.org/10.1080/13658810500391156 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27633 [article]

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An object-oriented data model for complex objects in three-dimensional geographical information systems / Wei Shi in International journal of geographical information science IJGIS, vol 17 n° 5 (july - August 2003)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 17 n° 5 (july - August 2003) . - pp 411 - 430 Titre : An object-oriented data model for complex objects in three-dimensional geographical information systems Type de document : Article/Communication Auteurs : Wei Shi, Auteur ; B. Yang, Auteur ; Qi Li, Auteur Année de publication : 2003 Article en page(s) : pp 411 - 430 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] analyse spatiale [Termes IGN] modèle 3D de l'espace urbain [Termes IGN] modèle conceptuel de données [Termes IGN] modèle orienté objet [Termes IGN] modélisation 3D [Termes IGN] objet géographique 3D [Termes IGN] objet géographique complexe [Termes IGN] primitive géométrique [Termes IGN] primitive volumique [Termes IGN] requête spatiale [Termes IGN] SIG 3D [Termes IGN] ville [Termes IGN] visualisation 3D Résumé : (Auteur) Developing a three-dimensional (3D) data model for Geographic Information Systems (GIS) is an essential and complex issue. 3D modelling in GIS is becoming ever more important for the development of cyber cities and digital earth, which have recently become feasible. A competent 3D model forms an efficient foundation for 3D visualization, query and spatial analysis. As a development of the existing 3D models, this study proposes particular improvements in handling complex 3D objects. We present an object-oriented data model for handling complex 3D objects in GIS. First, the conceptual data model is developed based on the principle of object-oriented (00) data modelling. This model is designed based on the following three basic geometric elements: node, segment and triangle. Accordingly, the abstract geometric objects are defined: including points, lines, surfaces and volumes. Second, the corresponding 3D logical model is designed based on the defined abstract objects and the relationships between them. Third, a formal representation of the 3D spatial objects is described in detail. Fourth, a prototype 3D GIS is developed based on the proposed 3D data model. Finally, we describe the results of an experimental study to reconstruct 3D objects using this 3D GIS and a comparison with the performance of other 3D data models. The proposed model is able to handle complex objects, such as complex buildings and TV towers, which is an essential functionality for building large-scale cyber cities, such as for Hong Kong. The proposed data model proves to be very efficient, particularly in visualization and rendering. The experimental results show which the data volume of the proposed model is compacted and the visualization speed for 3D objects is improved, compared with the existing models. Numéro de notice : A2003-142 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1080/1365881031000086974 En ligne : https://doi.org/10.1080/1365881031000086974 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22438 [article]

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