Functional land use maps are used for land evaluation, environmental analysis, and resource conservation. Spatial data clustering identifies the sparse and crowded places, thus discovering the overall distribution pat...Functional land use maps are used for land evaluation, environmental analysis, and resource conservation. Spatial data clustering identifies the sparse and crowded places, thus discovering the overall distribution pattern of the dataset. Some clustering methods represent an attribute-oriented approach to knowledge discovery. Other methods rely on natural notions of similarities （e.g., Euclidean distances）. These are not appropriate for constructing functional areas. We propose a similarity value to evaluate the closeness between a pair of points based on the total functional area and the proportion of the main land use type for the entire functional area. We develop constrained attributes employing this similarity value and a DT （Delaunay triangulation） criterion function when merging clusters. Four thresholds are set to ensure that functional areas have acceptable proportions, regular shapes, and no overlap. An experimental study was conducted with cadastral data for Chengdu, China, from 2009. The results show the advantages for objectivity and efficiency in using the proposed algorithm to define functional areas. The areas are created dynamically at any convenient time.展开更多
Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image pr...Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image processing and density-controlled Centroidal Voronoi tessellations to quickly generate a density-controlled constrained Delaunay triangulation lbr 2D sea area. Firstly, preprocess digital images of the sea area and extract the boundary of seawater region by eight-neighbor searching algorithm. Then, 1 use Odd-Even Testing＂ method to check if one random vertex is inside the boundary and insert random vertices into the boundary. Finally, we get the CDT of random vertices by density-controlled CVT-Lloyd method. We also give some comparisons with existing methods, and our method performs better in final restllt of triangulation.展开更多
3D reconstruction of terrain model based on digital line graphics (DLG) is discussed. An auto-coupling triangles algo-rithm based on triangle topological relationship is put forward, and the topological data model of ...3D reconstruction of terrain model based on digital line graphics (DLG) is discussed. An auto-coupling triangles algo-rithm based on triangle topological relationship is put forward, and the topological data model of complicated terrain is developed. Based on this data model, automatic 3D topological reconstruction of terrain is realized.展开更多
We tackle the problem of constructing 2D centroidal Voronoi tessellations with constraints through an efficient and robust construction of bounded Voronoi diagrams, the pseudo-dual of the constrained Delaunay triangul...We tackle the problem of constructing 2D centroidal Voronoi tessellations with constraints through an efficient and robust construction of bounded Voronoi diagrams, the pseudo-dual of the constrained Delaunay triangulation.We exploit the fact that the cells of the bounded Voronoi diagram can be obtained by clipping the ordinary ones against the constrained Delaunay edges.The clipping itself is efficiently computed by identifying for each constrained edge the(connected) set of triangles whose dual Voronoi vertices are hidden by the constraint.The resulting construction is amenable to Lloyd relaxation so as to obtain a centroidal tessellation with constraints.展开更多
文摘Functional land use maps are used for land evaluation, environmental analysis, and resource conservation. Spatial data clustering identifies the sparse and crowded places, thus discovering the overall distribution pattern of the dataset. Some clustering methods represent an attribute-oriented approach to knowledge discovery. Other methods rely on natural notions of similarities （e.g., Euclidean distances）. These are not appropriate for constructing functional areas. We propose a similarity value to evaluate the closeness between a pair of points based on the total functional area and the proportion of the main land use type for the entire functional area. We develop constrained attributes employing this similarity value and a DT （Delaunay triangulation） criterion function when merging clusters. Four thresholds are set to ensure that functional areas have acceptable proportions, regular shapes, and no overlap. An experimental study was conducted with cadastral data for Chengdu, China, from 2009. The results show the advantages for objectivity and efficiency in using the proposed algorithm to define functional areas. The areas are created dynamically at any convenient time.
基金Supported by National Natural Science Foundation of China(NSFC)(61572288,61373078)the Fundamental Research Funds of Shandong University(2015JC009)the Program for New Century Excellent Talents in University(NCET-13-0529)
文摘Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image processing and density-controlled Centroidal Voronoi tessellations to quickly generate a density-controlled constrained Delaunay triangulation lbr 2D sea area. Firstly, preprocess digital images of the sea area and extract the boundary of seawater region by eight-neighbor searching algorithm. Then, 1 use Odd-Even Testing＂ method to check if one random vertex is inside the boundary and insert random vertices into the boundary. Finally, we get the CDT of random vertices by density-controlled CVT-Lloyd method. We also give some comparisons with existing methods, and our method performs better in final restllt of triangulation.
文摘3D reconstruction of terrain model based on digital line graphics (DLG) is discussed. An auto-coupling triangles algo-rithm based on triangle topological relationship is put forward, and the topological data model of complicated terrain is developed. Based on this data model, automatic 3D topological reconstruction of terrain is realized.
文摘We tackle the problem of constructing 2D centroidal Voronoi tessellations with constraints through an efficient and robust construction of bounded Voronoi diagrams, the pseudo-dual of the constrained Delaunay triangulation.We exploit the fact that the cells of the bounded Voronoi diagram can be obtained by clipping the ordinary ones against the constrained Delaunay edges.The clipping itself is efficiently computed by identifying for each constrained edge the(connected) set of triangles whose dual Voronoi vertices are hidden by the constraint.The resulting construction is amenable to Lloyd relaxation so as to obtain a centroidal tessellation with constraints.
