The concept of the 'Regular Polytope' has been designed to facilitate the search for a rigorous closed algebra for the query and manipulation of the representations of spatial objects within the finite precisi...
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ISBN:
(纸本)9783540721345
The concept of the 'Regular Polytope' has been designed to facilitate the search for a rigorous closed algebra for the query and manipulation of the representations of spatial objects within the finite precision of a computer implementation. It has been shown to support, a closed, complete and useful algebra of connectivity, and support a topology, without assuming the avail-ability of infinite precision arithmetic. This paper explores the practicalities of implementing this approach both in terms of the database schema and in terms of the algorithmic implementation of the connectivity and topological predicates and functions. The problem domains of Cadastre and Topography have been chosen to illustrate the issues.
In order to adequately fulfil specific requirements related to spatial database integration with 3D modeling tools, this paper presents the development of a generic and open system architecture called Web Geological F...
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ISBN:
(纸本)9783540721345
In order to adequately fulfil specific requirements related to spatial database integration with 3D modeling tools, this paper presents the development of a generic and open system architecture called Web Geological Feature Server (WGFS). WGFS provides direct access through Web services to 3D geological models. WGFS is based on a three-tier architecture: a client (Gocad), an application server (Apache Tomcat and Deegree) and a DBMS (MySQL). This architecture takes advantage of standard-compliant spatial applications such as WFS and GML standards stemming from OGC and spatial schema from ISO TC/211-Geographic Information. Before introducing the architecture and motivations of some geoinformatics choices, we will remind Sol-fie important issues that have to be taken into account when such development is planned.
Modeling 3D geo-information has often been based on either simple extensions of 2D geo-information modeling principles without considering the additional 3D aspects related to correctness of representations or on 3D C...
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ISBN:
(纸本)9783540721345
Modeling 3D geo-information has often been based on either simple extensions of 2D geo-information modeling principles without considering the additional 3D aspects related to correctness of representations or on 3D CAD. based solutions applied to geo-information. Our approach is based from the scratch on modeling 3D geo-information based on the mathematically well-defined Poincare-TEN data structure. The feasibility of this approach still has to be verified in practice. In this paper, the first experiences of loading a reasonable sized data, set, comprised of about 1,800 buildings represented by nearly 170,000 tetrahedrons (including the 'air' and 'earth'), are discussed. Though the Poincare-TEN data structure is feasible, the experience gained during the implementation raises new research topics: physical storage in one (tetrahedron only) or two tables (tetrahedron and node), effective clustering and indexing improvements, more compact representations without losing too much performance, etc.
Advances in storage management and visualization tools have expanded the frontiers of traditional 2D domains like GIS to dimensions. Recent proposals such as CityGML and associated gateways bridge a long-standing gap ...
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ISBN:
(纸本)9783540721345
Advances in storage management and visualization tools have expanded the frontiers of traditional 2D domains like GIS to dimensions. Recent proposals such as CityGML and associated gateways bridge a long-standing gap between the terrestrial models from the GIS and the CAD/CAM worlds and shift the focus from 2D to 3D. As a result, efficient and scalable techniques for storage, validation and query of 3D models will become a key to terrestrial data management. In this paper, we focus on the problem of validation of 3D geometries. First we present Oracle's data model for storing 3D geometries (following the general OGC/ISO GML3 specifications). Then, we define more specific and refined rules for valid geometries in this model. We show that the solid representation is simpler and easier to validate than the CAM model but still retains the representative power. Finally, we present explicit examples of valid and invalid geometries. This work should make it to easy to conceptualize valid and invalid 3D geometries.
The neighbourhood aspect of city models is often overlooked in methods of generating detailed city models. This paper identifies two distinct styles of virtual city generation and highlights the weaknesses and strengt...
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ISBN:
(纸本)9783540721345
The neighbourhood aspect of city models is often overlooked in methods of generating detailed city models. This paper identifies two distinct styles of virtual city generation and highlights the weaknesses and strengths of both, before proposing a geo-demographically based solution to automatically generate 3D residential neighbourhood models suitable for use within simulative training. The algorithms main body of work focuses oil a classification based system which applies a texture library of captured building instances to extruded and optimised virtual buildings created from 2D GIS data.
This paper explores the state of the art in 3D city modelling and draws attention to the 'missing link' between models of buildings and models of the surrounding terrain. Without such integrated modelling, app...
ISBN:
(纸本)9783540721345
This paper explores the state of the art in 3D city modelling and draws attention to the 'missing link' between models of buildings and models of the surrounding terrain. Without such integrated modelling, applications that cross this divide are stalled. In this paper we propose a conceptual approach to this problem and set out a constraint-based solution to three dimensional modelling of buildings and terrains together.
Comprehensible and effective visualization of complex virtual 3D city models requires an abstraction of city model components to provide different degrees of generalization. This paper discusses generalization techniq...
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ISBN:
(纸本)9783540721345
Comprehensible and effective visualization of complex virtual 3D city models requires an abstraction of city model components to provide different degrees of generalization. This paper discusses generalization techniques that achieve clustering, simplification, aggregation and accentuation of 3D building ensembles. In a preprocessing step, individual building models are clustered into cells defined by, and derived from its surrounding infrastructure network such as streets and rivers. If the infrastructure network is organized hierarchically, the granularity of the cells can be varied correspondingly. Three fundamental approaches have been identified, implemented, and analyzed: The first technique uses cell generalization;from a given cell it extrudes a 3D block, whose height is calculated as the weighted average of the contained buildings,as optimization, outliers can be managed separately. The second technique is based on convex-hull generalization, which approximates the contained buildings by creating the convex hull for the building ensemble. The third technique relies on voxelization, which converts the buildings geometry into a regular 3D raster data representation. Through morphological operations and Gaussian blurring, aggregation and simplification is yielded;polygonal geometry is created through a marching cubes algorithm. The paper closes with conclusions drawn with respect to the characteristics and applicability of the presented generalization techniques for interactive 3D systems based on complex virtual 3D city models.
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