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61.
地图数据合并是地理空间数据集成的基本途径,同名实体匹配是其中的重点与难点。本文根据线实体的形状将其分为简单线实体与复杂线实体,提出针对前者以线实体端点与中点为发生元生成的Voronoi图所得到的邻近对应关系为依据、针对后者以基于线实体缓冲区重叠度构造的相似性测度指标为依据优化候选匹配集的思路,并设计与实现了相关算法。实证研究表明,该算法能够适应不同比例尺与不同时相的城市道路网地图数据同名实体匹配。 相似文献
62.
Transmission and visualization of large geographical maps 总被引:1,自引:0,他引:1
Liqiang Zhang Liang ZhangYingchao Ren Zhifeng Guo 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(1):73-80
Transmission and visualization of large geographical maps have become a challenging research issue in GIS applications. This paper presents an efficient and robust way to simplify large geographical maps using frame buffers and Voronoi diagrams. The topological relationships are kept during the simplification by removing the Voronoi diagram’s self-overlapped regions. With the simplified vector maps, we establish different levels of detail (LOD) models of these maps. Then we introduce a client/server architecture which integrates our out-of-core algorithm, progressive transmission and rendering scheme based on computer graphics hardware. The architecture allows the viewers to view different regions interactively at different LODs on the network. Experimental results show that our proposed scheme provides an effective way for powerful transmission and manipulation of large maps. 相似文献
63.
论述了在原Voronoi图的基础上增加点和删去点后生成新Voronoi图的算法.在增点过程中,针对新增加点后不满足Delaunay三角网特性的情况,利用最大最小角规则进行局部优化,根据优化后的三角网生成新Voronoi图;在删点过程中,针对删点的不同位置情况,修改相应Voronoi域,生成新Voronoi图. 相似文献
64.
在对Voronoi特性进行分析的基础上,运用Delaunay规则实现了海洋底质数据点的三角网化,从而间接生成了Voronoi图,再经过邻近区域的合并处理得到理想的底质划界区域。 相似文献
65.
66.
Priyanka Lal Vishnu Agarwal Parul Pruthi Swaranjit Singh Cameotra Vikas Pruthi 《洁净——土壤、空气、水》2008,36(12):963-968
The microbiological assessment of biofilm formation from paper mill effluent discharged through a pipeline revealed a maximum microbial count for Pseudomonas (5·106 cfu/mL) followed by Staphylococcus (4·106 cfu/mL), Bacillus (8.2·105 cfu/mL), Burkholderia (7.2·105 cfu/mL), Enterobacter (5.3·104 cfu/mL), Acinetobacter (4.1·103 cfu/mL), Alcaligenes (1.2·102 cfu/mL) and Klebsiella (0.8·102 cfu/mL) species. Among these species, the maximum biofilm formation was observed after 24 h of incubation by Pseudomonas sp. using a crystal violet (CV) assay. This isolate was later identified by 16S rRNA amplification to be Pseudomonas aeruginosa PME1. Extracellular polymeric substances (EPS) of P. aeruginosa PME1 in the biofilm showed a reduction in total carbohydrate content (42%) with increased protein (9.0%), hexosamine (3.0%) and uronic acid (1.7%) content as compared to its planktonic form. Antimicrobial susceptibility testing revealed that P. aeruginosa PME1 biofilms were 17, 24, 27, 30, and 32 times more resistant to cefotaxime, imipenem, ceftazidime, tazobactam and piperacillin, respectively, than their free flowing counterparts. 相似文献
67.
The solution of second order elliptic partial differential equations typically arising for flow problems, e.g., in porous media, is frequently expressed as face fluxes of a flow field at hexahedral cells. In this letter, we show by example that the following properties are incompatible: (1) A local velocity reconstruction, (2) reproduction of uniform flow for general hexahedral cells, and (3) a flow field in H(div). This is in particular relevant to mixed finite element methods approximating H(div), and to other methods trying to reconstruct a flow field in a hexahedron using only local face fluxes, e.g., streamline tracing methods for reservoir simulation. 相似文献
68.
69.
Christos Kastrisios Lysandros Tsoulos 《International journal of geographical information science》2018,32(8):1541-1557
Voronoi tessellation, and its dual the Delaunay triangulation, provide a cohesive framework for the study and interpretation of phenomena of geographical space in two and three dimensions. The planar and spherical solutions introduce errors in the positional accuracy of both Voronoi vertices and Voronoi edges due to errors in distance computations and the path connecting two locations with planar lines or great circle arcs instead of geodesics. For most geospatial applications the introduction of the above errors is insignificant or tolerable. However, for applications where the accuracy is of utmost importance, the ellipsoidal model of the Earth must be used. Characteristically, the introduction of any positional error in the delimitation of maritime zones and boundaries results in increased maritime space for one state at the expense of another. This is a situation that may, among others, have a serious impact on the financial activities and the relations of the states concerned. In the context of previous work on maritime delimitation we show that the Voronoi diagram constitutes the ideal solution for the development of an automated methodology addressing the problem in its entirety. Due to lack of a vector methodology for the generation of Voronoi diagram on the ellipsoid, the aforementioned solution was constrained by the accuracy of existing approaches. In order to fill this gap, in this paper we deal with the inherent attributes of the ellipsoidal model of the Earth, e.g. the fact that geodesics are open lines, and we elaborate on a methodology for the generation of the Voronoi diagram on the ellipsoid for a set of points in vector format. The resulting Voronoi diagram consists of vertices with positional accuracy that is only bounded by the user needs and edges that are comprised of geodesics densified with vertices equidistant to their generators. Finally, we present the implementation of the proposed algorithm in the Python programming language and the results of two case studies, one on the formation of closest service areas and one on maritime boundaries delimitation, with the positional accuracy set to 1 cm. 相似文献
70.
Hiroyuki Usui Yasushi Asami 《International journal of geographical information science》2018,32(1):120-139
The size distribution of urban blocks is important for the characterisation of urban block patterns and is known to follow several parametric statistical distributions. However, it has not previously been analysed on the basis of a normative plane tessellation and in terms of urban block density and mean road width. In this article, we formulate the size distribution of Voronoi cells using the gamma distribution estimated by urban block density and mean road width. We found that (1) both log-normal and gamma distributions can be good candidates for the size distribution of urban blocks at the scale of a region that consists of regular urban blocks and that has a uniform road width; and (2) the size distribution of urban blocks depends on the balance between pattern and width improvement effects. Based on one study region in Tokyo, if the pattern improvement effect is more prominent than the width improvement effect, the mode of urban block sizes tends to be larger than if it is not. These findings are expected to provide scientific support for urban planning (e.g. land readjustment projects). 相似文献