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排序方式: 共有230条查询结果,搜索用时 156 毫秒
101.
一种有效的离散数据场等值线生成方法 总被引:1,自引:0,他引:1
给出了一种有效的离散数据三角形网格等值线生成算法,首先在Delaunay三角剖分算法中引入了闭合点概念,通过在三角形网格生成过程中动态删除闭合点,减少搜索点集大小,提高了原来三角形剖分算法的速度;其次在三角形网格等值线生成算法中提出了凸边和凸边三角形的概念,通过建立凸边链表和凸边三角形链表,并以凸边进行等值线跟踪,简化了三角形网格等值线搜索算法,提高了等值线生成效率。最后在气象天气图离散站点数据基础上给出了详细测试数据,并给出了天气图等值线绘制效果图。 相似文献
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MAST-2D diffusive model for flood prediction on domains with triangular Delaunay unstructured meshes
A new methodology for the solution of the 2D diffusive shallow water equations over Delaunay unstructured triangular meshes is presented. Before developing the new algorithm, the following question is addressed: it is worth developing and using a simplified shallow water model, when well established algorithms for the solution of the complete one do exist?The governing Partial Differential Equations are discretized using a procedure similar to the linear conforming Finite Element Galerkin scheme, with a different flux formulation and a special flux treatment that requires Delaunay triangulation but entire solution monotonicity. A simple mesh adjustment is suggested, that attains the Delaunay condition for all the triangle sides without changing the original nodes location and also maintains the internal boundaries. The original governing system is solved applying a fractional time step procedure, that solves consecutively a convective prediction system and a diffusive correction system. The non linear components of the problem are concentrated in the prediction step, while the correction step leads to the solution of a linear system of the order of the number of computational cells. A semi-analytical procedure is applied for the solution of the prediction step. The discretized formulation of the governing equations allows to handle also wetting and drying processes without any additional specific treatment. Local energy dissipations, mainly the effect of vertical walls and hydraulic jumps, can be easily included in the model.Several numerical experiments have been carried out in order to test (1) the stability of the proposed model with regard to the size of the Courant number and to the mesh irregularity, (2) its computational performance, (3) the convergence order by means of mesh refinement. The model results are also compared with the results obtained by a fully dynamic model. Finally, the application to a real field case with a Venturi channel is presented. 相似文献
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利用约束D-TIN进行建筑物多边形凹部结构识别与渐进式化简 总被引:1,自引:0,他引:1
分析了位于建筑物多边形外侧的凹部结构特征及其类型,探讨了一种基于凹部层次结构的建筑物多边形渐进式化简方法,即以三角形为形状基元,用约束Delaunay三角化方法对建筑物多边形进行空间剖分,从凹部三角形树中提取三角形序列,通过匹配特征序列识别凹部的基本模式,以确定和实施相应的凹部化简方法,在此基础上迭代执行识别-化简过程,以实现对建筑物复杂凹部的渐进式化简。实验分析表明,该方法具有结构化和渐进综合的特点。 相似文献
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针对环境与灾害监测预报小卫星(HJ)图像存在较大整体几何误差,且无规律可循,难以使用全局模型模拟整景图像几何变形,而基于手动方式选取控制点的全局模型和局部模型都不适合于HJ图像几何精纠正的问题,提出一种基于加速分段测试特征(features from accelerated segment test,FAST)算法测点并用局部模型进行几何精纠正的优化方法。首先以FAST算法获取大量地面控制点(ground control point,GCP);再使用多项式模型对GCP的均方根误差阈值、潜在不匹配和实际不匹配GCP数量进行相关分析,据此修正FAST参数,筛查GCP误点;最后使用局部模型完成几何精纠正。此外,使用散点图和空间插值等方法建立适合于HJ图像几何精纠正结果的评价指标。检验结果表明,该方法能使纠正误差控制在1.5个像元内,纠正后的图像能满足中分辨率尺度的应用要求。 相似文献
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Ai Tinghua 《地球空间信息科学学报》2013,16(2):55-62
This paper presents a field based method to deal with the displacement of building cluster, which is driven by the street widening. The compress of street boundary results in the force to push the building moving inside and the force propagation is a decay process. To describe the phenomenon above, the field theory is introduced with the representation model of isoline. On the basis of the skeleton of Delaunay triangulation, the displacement field is built in which the propagation force is related to the adjacency degree with respect to the street boundary. The study offers the computation of displacement direction and offset distance for the building displacement. The vector operation is performed on the basis of grade and other field concepts. 相似文献