Digital Terrain Models are necessary for the simulation of flood events. Therefore they have to be available for creating flood risk maps. River embankments for flood protection have been in use for centuries. Althoug...
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ISBN:
(纸本)9783540721345
Digital Terrain Models are necessary for the simulation of flood events. Therefore they have to be available for creating flood risk maps. River embankments for flood protection have been in use for centuries. Although they are artificial structures that actually do not belong to the natural elements of the land they are usually implicitly embedded in digital terrain data. Being elongated and elevated objects, they appear - depending oil the used colour ramp for visualisation - as bright stripes on the surrounding background. For purposes of flood protection it might be useful to gain data about crest levels, especially if these information are not available from other sources. High resolution Digital Terrain Models (DTM) can be used as highly reliable sources for deriving dike heights. Using laser scanner technique a general height accuracy of about 10-15 cm can be achieved for elevation models. Thus, by analysing DTM data relevant geometrical information on dikes can be directly derived.
The 3DIM (3D Integrated Model) is an information model under development which intends to integrate geographic features on the earth surface as well as above and below the earth surface into a common semantic-geometri...
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ISBN:
(纸本)9783540721345
The 3DIM (3D Integrated Model) is an information model under development which intends to integrate geographic features on the earth surface as well as above and below the earth surface into a common semantic-geometric model. We present and discuss two alternative implementations of the information model for DBMS. In the first alternative semantics are separated from geometry and organized into two table groups while in the second alternative semantic tables incorporates the geometry of the objects.
Current environmental impact studies supporting environmental policies are mostly based on a 2D approach. The - mostly 3D - output of software that, calculates the specific phenomenon (e.g. air or noise pollution) is ...
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ISBN:
(纸本)9783540721345
Current environmental impact studies supporting environmental policies are mostly based on a 2D approach. The - mostly 3D - output of software that, calculates the specific phenomenon (e.g. air or noise pollution) is processed and visualised in 2D and combined with 2D topographical and other data, such as population distribution, to quantify the effects. The research described in the paper aimed at improving visualisation and quantification of impact of continuous spatial phenomena on the environment by applying a 3D approach. Noise is taken as example. Based on the specific demand, an approach is presented to generate a 3D noise map as basis for noise impact studies. The proposed concept is proofed by applying it to a sample noise impact study. From experiences with the sample it can be concluded that the 3D noise map offers insight into the 3D noise situation where 2D noise maps have limitations. In addition more accurate assessment of noise impact is possible in particular when different floors of a building close to the noise source and/or behind noise barriers are considered, which is specifically relevant in urban areas. The proposed methodology can be applied to other continuous spatial phenomena so that it meets the more general problem of how to represent 3D aspects of environmental impact studies.
Airborne Laser Surveying (ALS) or LIDAR (Light Detection and Ranging) becomes more and more popular because it provides a rapid 3D data collection over a massive area. The captured 3D data contains terrain models, for...
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ISBN:
(纸本)9783540721345
Airborne Laser Surveying (ALS) or LIDAR (Light Detection and Ranging) becomes more and more popular because it provides a rapid 3D data collection over a massive area. The captured 3D data contains terrain models, forestry, 3D buildings and so on. Current research combines other data resources on extracting building information or uses pre-defined building models to fit the roof structures. However we want to find an alternative solution to reconstruct the 3D buildings without any, additional data sources and predefined roof styles. Therefore our challenge is to use the captured data only and covert them into CAD-type models containing walls, roof planes and terrain which can be rapidly displayed from any 3D viewpoint.
We present an automatic approach to create building models from terrestrial laser points. Our method starts by extracting important building features (wall, window, roof, door, extrusion) from segmented terrestrial po...
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ISBN:
(纸本)9783540721345
We present an automatic approach to create building models from terrestrial laser points. Our method starts by extracting important building features (wall, window, roof, door, extrusion) from segmented terrestrial point cloud. Then visible building geometries are recovered by direct fitting polygons to extracted feature segments. For the occluded building parts, geometric assumptions are made from visible parts and knowledge about buildings. Finally solid building models can be obtained by combining directly fitted polygons and assumptions for occluded parts. This approach achieves high automation, level of detail, and accuracy.
Terrains are often modeled by triangulations, which ideally should have 'nice shape' triangles and reality of drainage in terrains (few local minima and drainage lines in the bottoms of valleys). Delaunay tria...
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ISBN:
(纸本)9783540721345
Terrains are often modeled by triangulations, which ideally should have 'nice shape' triangles and reality of drainage in terrains (few local minima and drainage lines in the bottoms of valleys). Delaunay triangulation is a good way to formalize nice shape, and if higher-order Delaunay triangulations are used, drainage reality can be achieved. Two heuristics are presented, one for reducing the number of local minima and one for reducing the number of valley edges and components. The empirical results show how well they perform on real-world data;on average we see a 16% improvement over known algorithms.
We consider, in this paper, the problem of reconstructing the surface from contour lines of a topographic map. We reconstruct the surface by approximating the elevations, as specified by the contour lines, by tensor-p...
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ISBN:
(纸本)9783540721345
We consider, in this paper, the problem of reconstructing the surface from contour lines of a topographic map. We reconstruct the surface by approximating the elevations, as specified by the contour lines, by tensor-product cubic B-splines using the least squared-error criterion. The resulting surface is both accurate and smooth and is free from the terracing artifacts that occur when thin-plate splines are used to reconstruct the surface. The approximating surface, S(x,y), is a linear combination of tensor-product cubic B-splines. We denote the second-order partial derivatives of S by S(xx), S(xy) and S(yy). Let h(k) be the elevations at. the points (x(k),y(k)) on the contours. S is found by minimising the sum of the squared-errors {S(x(k),y(k))-h(k)}(2) and the quantity integral integral S(xx)(2)(x, y) + 2S(xy)(2)(x, y) + S(yy)(2) (x, y) dydx, the latter weighted by a constant lambda. Thus, the coefficients of a small number of tensor-product cubic B-splines define the reconstructed surface. Also, since tensor-product cubic B-splines are non-zero only for four knot-intervals in the x-direction and y-direction, the elevation at any point can be found in constant time and a grid DEM can be generated from the coefficients of the B-splines in time linear in the size of the grid.
3D spatial modeling is one of the most important, issues in 3D CIS research. It involves the definition of spatial objects, data models, and attributes for visualization, interoperability and standards. Real world com...
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ISBN:
(纸本)9783540721345
3D spatial modeling is one of the most important, issues in 3D CIS research. It involves the definition of spatial objects, data models, and attributes for visualization, interoperability and standards. Real world complexity leads to different modeling approaches, as seen in different CIS applications. This paper provides some review of the problems, challenges and issues pertaining to the 3D CIS problems, especially in the handling and managing of 3D solids in DBMS. The paper also describes 3D spatial operators in DBMS and presents results using a simulation dataset. At the end of the paper, we provide and highlight requirements and recommendations for future research.
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