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Merging R-trees: efficient strategies for local bulk insertion / L. Chen in Geoinformatica, vol 6 n° 1 (March - May 2002)
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Titre : Merging R-trees: efficient strategies for local bulk insertion Type de document : Article/Communication Auteurs : L. Chen, Auteur ; R. Choubey, Auteur ; E.A. Rundensteiner, Auteur Année de publication : 2002 Article en page(s) : pp 7 - 34 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées
[Termes IGN] arbre-R
[Termes IGN] index spatial
[Termes IGN] indexation spatiale
[Termes IGN] intégration de données
[Termes IGN] jeu de données localisées
[Termes IGN] requête spatialeRésumé : (Auteur) A lot of recent work has focussed on bulk loading of data into multidimensional index structures in order to efficiently construct such structures for large data sets. In this paper, we address this problem with particular focus on R-trees - which are an important class of index structures used widely in commercial database systems. We propose a new technique, which as opposed to the current technique of inserting data one by one, bulk inserts entire new data sets into an active R-tree. This technique, called STLT (for small-tree-large-tree), considers the new data set as an R-tree itself (small tree), identifies and prepares a suitable location in the original R-tree (large tree) for insertion, and lastly performs the insert of the small tree into the large tree. Besides an analytical cost model of STLT, extensive experimental studies both on synthetic and real GIS data sets are also reported. These experiments not only compare STLT against the conventional technique, but also evaluate the suitability and limitations of STLT under different conditions, such as varying buffer sizes, ratio between existing and new data sizes, and skewness of new data with respect to the whole spatial region. We find that STLT does much better (in average, about 65%) than the existing technique for skewed data sets as well for large sizes of both the large tree and the small tree in terms of insertion time, while keeping comparable query tree quality. STLT consistently outperforms the alternate technique in all other circumstances in terms of bulk insertion time, especially, even up to 2,000% for the cases when the area of new data sets covers up to 4% of the global region covered by the existing index tree; however, at the cost of a deteriorating resulting tree quality. Numéro de notice : A2002-107 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1023/A:1013764014000 En ligne : https://doi.org/10.1023/A:1013764014000 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22022
in Geoinformatica > vol 6 n° 1 (March - May 2002) . - pp 7 - 34[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 057-02011 RAB Revue Centre de documentation En réserve L003 Disponible GPS network monitors the Western Alp's deformation over a five-year period: 1993-1998 / Christophe Vigny in Journal of geodesy, vol 76 n° 2 (February 2002)
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Titre : GPS network monitors the Western Alp's deformation over a five-year period: 1993-1998 Type de document : Article/Communication Auteurs : Christophe Vigny, Auteur ; J. Chery, Auteur ; Thierry Duquesnoy , Auteur ; et al., Auteur
Année de publication : 2002 Article en page(s) : pp 63 - 76 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Alpes occidentales
[Termes IGN] déformation de la croute terrestre
[Termes IGN] montagne
[Termes IGN] positionnement par GPS
[Termes IGN] surveillance géologique
[Termes IGN] tectonique
[Termes IGN] triangulation (topologie)Résumé : (Auteur) The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic problems still remain to be Occidental Alps, the repartition of the deformation between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale GPS surveyed in 1993 and 1998 with a minimum observation of 3 days at each site. GPS data processing has been done by three independent teams using different soft-ware. The different solutions have horizontal repeat-abilities (N-E) of 4-7 min in 1993 and 2-3 mm in 1998 and compare at the 3-5-mm level in position and 2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally smaller than 2 mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem to suggest that the N-S compression of the Western Alps is quite mild (less than 2 mm/yr) compared to the global convergence between the African and Eurasian plate (6 mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation of the Maghrebids and/ or by rotations of Mediterranean microplates. Also, EW velocity components analysis supports the idea that E-W extension exists, as already suggested by recent structural and seismotectonic data interpretation Numéro de notice : A2002-018 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-001-0231-8 En ligne : https://doi.org/10.1007/s00190-001-0231-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=21935
in Journal of geodesy > vol 76 n° 2 (February 2002) . - pp 63 - 76[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-02021 RAB Revue Centre de documentation En réserve L003 Disponible
Titre : 3D terrain models on the basis of a triangulation Type de document : Thèse/HDR Auteurs : Norbert Pfeifer, Auteur Editeur : Vienne [Autriche] : Technische Universität Wien Année de publication : 2002 Collection : Geowissenschaftliche Mitteilungen, ISSN 1811-8380 num. 65 Importance : 142 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-9500791-7-3 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique
[Termes IGN] données localisées 3D
[Termes IGN] interpolation
[Termes IGN] modèle numérique de terrain
[Termes IGN] noeud
[Termes IGN] reconstruction 3D
[Termes IGN] triangulation de DelaunayRésumé : (Auteur) This work provides an overview on terrain modelling techniques. Terrain models, or in order to be more general, topographic surface models, play an important role in many fields of science and practice where a relation to a location, i.e. a geo-relation' is given. These models describe the height as a function of the location. There lies a restriction in this definition, because only one height is allowed at one ground-plane position. Therefore, the currently used models are often termed 2.5D terrain models. The modelling of overhangs is not possible within such an approach. The aim of this work is to put aside this limitation and provide methods for 3D terrain modelling where not only the above restrictions do not apply anymore, but also more general surfaces with tunnels and cave systems can be reconstructed. Another terrain property which plays an important role in this work is its smoothness: a model shall be smooth. An exception is introduced at so-called breaklines where the terrain shape has a sharp edge.
There are several ways in order to build terrain models with the above characteristics (fully 3D and smooth). In this work, emphasis is put on those approaches which reconstruct the surface on the basis of a triangulation. Two different techniques are treated with great detail: the patch work and the subdivision approach. For each of those two, one method was developed which considers the special requirements in terrain modelling. The main contribution of this work to terrain modelling are those new methods. Generation, improvement, and thinning of triangulations is not treated within this work, but references to the relevant literature are given. Generally, the reconstruction of a patch work proceeds as follows. Given is a triangulation, which has as expected planar faces. For each edge a curve is determined which interpolates the end points. In the next step, triangular patches are inserted into a triple of boundary curves spanned over the edges of each triangle. As the patches interpolate the boundary curve a G0 surface (a geometrically continuous surface) is obtained.
However, this is not enough, because a smooth surface (G1, geometric continuity of order one, i.e. tangent plane continuity) is desired. Adjacent patches must therefore interpolate not only the boundary curves, but also share a common field of cross boundary derivatives. This is the general approach for patch work surfaces.
The patch work method which is proposed in this work1 starts with an enhancement of the triangulation. As the measurement of terrain points and lines is always burdened with random errors (depending on the measurement device characteristics) these errors should be removed first. This can be achieved by kriging, whereby for each point of the triangulation (i.e. each vertex) a filter value is determined from its neighboring points. In this step also the surface normal vectors in the points can be estimated, but alternative methods for the estimation of the normal vector, e.g. by averaging those of the triangles which are incident to that vertex, are possible, too. Now, not only the position, but also the surface normal vector is prescribed for each vertex. The patches which are to be reconstructed over each face of the triangulation shall be polynomials of degree four and they are described with Beziér triangles which allow a geometric interpretation of the coefficients of the (bivariate) polynomial. In the next step, boundary curves of polynomial degree three are computed which replace' the edges of the triangulation. These curves interpolate the end points of the edge and the curve tangents in those points are perpendicular to the estimated normal vectors. This determines the boundaries of each patch. The missing parameters (i.e. coefficients of the polynomial) influence the shape in the interior of the patch and also the tangent planes of the patch along the boundaries. A field of normal vectors is estimated for each boundary curve by blending the normal vectors from the end points into each other. The inner' parameters of a patch are now determined in a way that the normal vector fields are approximately perpendicular to the tangent planes of the patch along the boundaries in a least squares sense. As this field is only' approximated and not interpolated this scheme is called "G1 (i.e. approximately tangent plane continuous).
The second technique for surface reconstruction over a triangulation is the so-called subdivision. In this approach the given triangulation is refined in steps, and in each step new vertices and edges are inserted into the triangulation. This is performed in a way that the smoothness of the triangulation is increased in each level, the angles between adjacent triangles converge towards 180_. The limit surface, reached after an infinite number of subdivision steps, is smooth. An advantage of this approach is that the surface description is always composed of small triangles which allows to apply simple algorithms for intersections and similar tasks. The size of the triangles depends on the number of subdivision steps (i.e. the refinement level). This is the general approach for subdivision surfaces.
Also in the reconstruction technique (developed in this work) for topographic surfaces which is based on subdivision a removal of random measurement errors has to be performed first. The refinement rule applied here is the so-called edge midpoint subdivision where in one step one vertex is inserted into each edge and the triangulation is updated. The subdivision is based on the estimation of local surfaces in each vertex. A local surface is estimated which approximates the vertex of interest and its neighbors. The co-ordinates of the new points are obtained by averaging the two local surfaces in either edge end point. To achieve this, a point, representative for the edge midpoint, is computed on both local surfaces and the mean of these two is the new point. Also the old' points obtain new co-ordinates, namely their position on the local approximating surfaces. Special modifications are introduced in order to interpolate the originally given points. The approaches are compared to each other with examples based on real photogrammetric and geodetic observations as well as on synthetic terrain data. It turns out that the surfaces obtained by the developed subdivision approach meet the requirements in topographic terrain modelling better.Note de contenu : 1 Introduction
2 Modelling of Topographic Surfaces
2.1 Types of Models
2.1.1 Contour lines
2.1.2 Bivariate functions
2.1.3 Volumetric models
2.1.4 Transformation between models
2.2 Global and local approaches
2.3 Models in 2.5D and in 3D
2.4 3D terrain models
2.4.1 Problem definition
3 Algorithms for Triangulations
3.1 Definition of neighborhood
3.2 Parameterization of triangulations
3.2.1 Projection onto a plane
3.2.2 Local projection onto a plane
3.2.3 Global parameterizations
3.2.4 A method for local parameterization
3.3 Surface approximation and estimation of geometric properties
3.3.1 Normal vectors and tangent planes
3.3.2 Approximating quadric as local surface description
3.3.3 Approximating second order polynomial as local surface description
3.4 Functionals and variational principle
3.5 Mesh improvement
3.6 Filtering of random measurement errors
3.7 Consideration of breaklines and special points
3.7.1 Neighborhood restrictions
3.7.2 Prescribed tangent planes
3.7.3 Surfaces and lines at special points
4 Parametric patches
4.1 Patches and patch work
4.2 Method overview
4.3 An "G1-continuous polynomial patch
4.3.1 Approximate continuity
4.3.2 Construction of a curve network
4.3.3 Insertion of patches
4.3.4 Insertion of patches and minimizing energy
4.3.5 Additional splitting
4.3.6 Results
5 Subdivision
5.1 The subdivision paradigm
5.2 Method overview
5.3 Subdivision by estimation of local surfaces
5.3.1 The curve case
5.3.2 Surface subdivision with approximating surfaces
5.3.3 Paraboloids vs. general quadrics as local surfaces
5.3.4 Paraboloids vs. second order polynomials as local surfaces
5.3.5 Interpolation and Approximation
5.3.6 Averaging
5.3.7 Roughness detection
5.3.8 Results
6 Examples
6.1 Vertical Wall
6.2 Data set “Elev”
6.3 Breaklines only
6.4 Data set “Albis”
6.5 Bridge
7 Conclusions and Perspectives
7.1 Applications
7.2 Enclaves
7.3 Concluding remarkNuméro de notice : 14314 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Note de thèse : PhD : Vermessung und Geoinformation : Technische Universität Wien : 2002 En ligne : https://repositum.tuwien.at/handle/20.500.12708/390?mode=simple Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62656 Analyse de données acquises par laser aéroporté pour la reconstruction 3D de scènes urbaines / R. Elkharroubi (2002)
Titre : Analyse de données acquises par laser aéroporté pour la reconstruction 3D de scènes urbaines Type de document : Mémoire Auteurs : R. Elkharroubi, Auteur Editeur : Champs/Marne : Université de Marne-la-Vallée Année de publication : 2002 Autre Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Importance : 43 p. Format : 21 x 30 Note générale : Bibliographie
Mémoire de fin de stage de DEA sciences de l'information géographiqueLangues : Français (fre) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] détection du bâti
[Termes IGN] diagramme de Voronoï
[Termes IGN] données altimétriques
[Termes IGN] données laser
[Termes IGN] écho multiple
[Termes IGN] extraction automatique
[Termes IGN] filtrage du bruit
[Termes IGN] GPS-INS
[Termes IGN] indice de végétation
[Termes IGN] modèle numérique de surface
[Termes IGN] modèle numérique de terrain
[Termes IGN] reconstruction 3D du bâti
[Termes IGN] semis de points
[Termes IGN] Stuttgart
[Termes IGN] sursol
[Termes IGN] système d'information géographique
[Termes IGN] télémètre laser aéroporté
[Termes IGN] télémétrie laser aéroporté
[Termes IGN] traitement d'image
[Termes IGN] triangulation de Delaunay
[Termes IGN] VRMLIndex. décimale : DSIG Mémoires du master 2 IG, du master 2 SIG, de l'ex DEA SIG Résumé : (Auteur) Le levé par le système laser aéroporté est une nouvelle technique d'acquisition des données 3D du terrain, le principe de ce système est fondé sur la mesure de la distance de l'avion au sol par un télémètre laser positionné et orienté par des récepteurs GPS et une station de navigation inertielle INS. En temps presque réel, les données acquises sont traitées suivant des modèles mathématiques afin d'obtenir les coordonnées planimétriques et altimétriques des nuages de points. Après une présentation du principe du système laser aéroporté et les différentes techniques permettant la séparation des points entre sol et sur-sol, ce mémoire décrit les différentes étapes de la nouvelle approche mise en oeuvre pour la classification des nuages de points en trois classes : sol, bâti et végétation, qui s'appuie principalement sur l'utilisation des échos multiples. Les résultats obtenus par un test de notre algorithme sur une zone d'étude sur la ville de Stuttgart ont permis de conclure que les échos multiples sont une source d'information primordiale pour l'extraction automatique des éléments de sur-sol à partir d'un modèle numérique de surface (MNS). Note de contenu : CHAPITRE 1 : LE SYSTEME LASER AEROPORTE
1-1 INTRODUCTION
1-2 COMPOSANTES DU SYSTEME DE MESURE LASER SCANNER
- Le télémètre laser - le système GPS - le système de navigation inertiel (INS)
1-3 TECHNIQUES DE BALAYAGE
1-4 PRINCIPE ET DETECTION DES ECHOS MULTIPLES
1-5 CALCUL DE LA POSITION 3D ET AJUSTEMENT DES BANDES
1-6 CARACTERISTIQUES DE QUELQUES CAPTEURS
1-7 APPLICATIONS
- Aménagement urbain et environnemental - études topographiques - cartographie des couloires linéaires - surveillance des zones côtières
1-8 CONCLUSION
CHAPITRE 2 : METHODES DE CLASSIFICATION DES DONNEES LASER
2-1 INTRODUCTION
2-2 TECHNIQUE DE LA MORPHOLOGIE MATHEMATIQUE
- Définition - séparation de sol et sur-sol par ouverture morphologique - limites de couverture morphologique
2-3 TECHNIQUE DE LA TRIANGULATION ADAPTATIVE
- Principe de la technique - limites de la technique
2-4 ETUDES DES ECHOS MULTIPLES
- Extraction des bâtiments - Extraction de la végétation
2-5 CONCLUSION
CHAPITRE 3 REPRESENTATION DES DONNEES ALTIMETRIQUES
3-1 INTRODUCTION
3-2 MODELE NUMERIQUE DE SURFACE
- Source de l'information altimétrique
- Mode de représentation des modèles numériques de surface (Mode image, Mode vecteur)
3-3 TRIANGULATION DE DELAUNAY
- Définition de la triangulation - Diagramme de Voronoï - construction de la triangulation de Delaunay
3-4 VISUALISATION VRML DE LA ZONE CHOISIE
- Langage VRML - présentation de la zone
3-5 PRESENCE DES ECHOS MULTIPLES
3-6 CONCLUSION
CHAPITRE 4 : ETAPES DE LA NOUVELLE APPROCHE DE CLASSIFICATION & DISCUSSION DES RESULTATS
4-1 INTRODUCTION
4-2 DETECTION DE LA VEGETATION
4-3 DETECTION DES BATIMENTS
- Sélection des premiers germes - propagation de la triangulation - recherche des deuxièmes germes - recherche des troisièmes germes et propagation finale
4-4 ETIQUETAGE DES BATIMENTS
- Principe - résultats
CONCLUSION ET PERSPECTIVESNuméro de notice : 11874 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Mémoire Master 2 IG Organisme de stage : Laboratoire du traitement du signal et d'image ; Ecole Nationale Supérieure des Télécommunications Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=49776 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 11874-01 DSIG Livre Centre de documentation Travaux d'élèves Disponible 11874-02 DSIG Livre Centre de documentation Travaux d'élèves Disponible
Titre : Etude de l'efficacité d'un réseau de transports : application au réseau métropolitain parisien Type de document : Mémoire Auteurs : M. Fouillet, Auteur Editeur : Paris : Université de Paris 9 Paris-Dauphine Année de publication : 2002 Importance : 98 p. Format : 21 x 30 cm Note générale : Bibliographie
[Mémoire] IUP génie mathématique et informatiqueLangues : Français (fre) Descripteur : [Vedettes matières IGN] Aménagement
[Termes IGN] accessibilité
[Termes IGN] ArcView
[Termes IGN] efficacité
[Termes IGN] graphe
[Termes IGN] réseau métropolitain
[Termes IGN] S-PLUSIndex. décimale : MX Mémoires divers Résumé : (Documentaliste) Afin d'étudier dans quelle mesure, un réseau de transport peut être affecté par des risques de dysfonctionnements, le réseau métropolitain parisien est choisi pour être modélisé sous forme de graphes. Des indices d'accessibilité rapportés à un réseau idéal planaire permettent d'évaluer le réseau de manière qualitative et quantitative. Les stratégies d'endommagement du réseau sont aussi recherchées au niveau des stations et des arcs de liaison entre stations. Ensuite, le fonctionnement perturbé du réseau est analysé avec S-plus et ArcView. Le rôle majeur de certains axes au sein du réseau est mis en avant. Numéro de notice : 13136 Affiliation des auteurs : non IGN Thématique : URBANISME Nature : Mémoire Organisme de stage : COGIT (IGN) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=49893 Réservation
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