共查询到20条相似文献，搜索用时 91 毫秒
1.
《地理与地理信息科学》2016,(1)
随着地理信息系统应用的深入,在真三维空间中处理问题已成为一种趋势,而实时阴影对提高三维场景的真实感和沉浸感非常重要。目前主流的平行分割阴影图算法对大尺度场景兼容性好,但在细节层次的渲染方面质量不高,而光源空间透视阴影图算法在细节层次渲染方面精度很高,但是对大尺度场景难以覆盖。针对该问题,提出了一种基于光源空间透视的平行分割阴影图算法,也称为光源透视平行分割阴影图算法。该方法将光源空间透视阴影图算法中透视锥体的透视变换矩阵应用于平行分割阴影图算法对各个子视锥体的渲染阶段并生成产生形变的阴影深度图,通过该方法减小其阴影走样误差。并且在计算透视变换矩阵的过程中,提出了一种确定阴影图形变程度的算法,使该算法更好地适应于不同大小的场景。实验结果表明,该算法通过提高视锥体近平面附近阴影采样率有效地解决了在平行分割阴影图算法中存在的阴影透视走样的问题。在对大规模场景的渲染方面,该算法在细节层次的表现要明显优于平行分割阴影图算法,满足了大尺度场景和精细建筑模型的阴影渲染需求。 相似文献
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该文阐述了透视坐标系的概念，列举了多种透视坐标网中量化信息的图解实例，力求进一步丰富和提高专题地图图形可视化的表现能力。 相似文献
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相机畸变是影响基于图像的几何量测、三维重建精度的重要因素之一。空间中一条直线在透视投影作用下理应成为一条直线,但因畸变其构象发生弯曲,通过场景信息中共线点的透视投影不变性可以求解出相机径向畸变系数。考虑畸变的渐变特性,该文设计了基于数位的相机径向畸变参数解算方法:将相机一阶径向畸变系数k1用科学计数法X×10-m表示,依次确定其指数m及尾数X,直至满足精度的设定,最终求解出k1的值。最后通过模拟和实例数据对该方法进行了分析验证。 相似文献
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从魁北克2000-世纪湿地大事件活动看21世纪国际湿地科学研究的热点与前沿 总被引：24，自引：6，他引：24
介绍了魁北克 2 0 0 0 -世纪湿地大事件活动的主要内容和信息 ,结合收集到的国际上新的湿地研究文献资料 ,总结了国际湿地科学研究的前沿领域、热点、主要研究进展和发展趋势 ,对国际湿地科学研究进展加以简要概述 ,以此透视现代国际湿地科学研究一些新的动向和趋势。 相似文献
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煤炭开发点燃了人类文明烛火,带来了经济和社会的繁荣,又造成了矿山环境破坏,束缚了经济和社会的可持续发展。透视煤炭开发对矿山环境的破坏问题, 旨在树立和落实科学发展观,应用生态经济学原理和循环经济理念, 指导煤炭综合开发,促进延伸煤炭 相似文献
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江苏省中北部区域发展战略研究——兼论江苏省的南北差异 总被引：2，自引：1，他引：2
不平衡战略的实施使江苏的南北差异迅速扩大，苏北发展严重滞后，本文首先分析了江苏省南北区域差异的特征和成因；在透视国内外产业结构演进趋势的基础上，论证了苏中苏北的相对优势；最后，提出了苏中苏北区域发展的若干战略。 相似文献
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在地理教学中,地理教学设计是落实探究性教学理念的一个非常重要的环节。为了帮助一线地理教师更好地理解和把握探究性教学．笔者翻译了美国伊利诺伊州（Illinois）FredWalk老师为K9-12（高中阶段）学生设计的“美国人口密度透视”案例。该案例充分体现了探究性教学的理念。 相似文献
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基础设施与人类生存环境之关系研究 总被引：3，自引：0，他引：3
人类在其发展过程中倾注了大量的人力、物力、财力建设基础设施,希图构筑理想生存环境.但基础设施为人类带来了什么?对人类的发展产生了何种影响?如何认识基础设施在人类生存环境演化中的作用?本文从积极角度阐述了基础设施与人类生存环境之关系,透视了基础设施在活动空间扩展、资源共享和生存环境优化方面的作用与意义. 相似文献
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杭州街巷地名丰富多彩,它的由来与杭州的地理环境、文物古迹、历史典故、风土人情,以及政治、经济发展等有着密切的关系。对杭州现行地名进行渊源分析,可以从不同侧面透视杭州历史文化名城的地域特色和丰富内涵。 相似文献
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Ikechukwu Maduako Monica Wachowicz 《International journal of geographical information science》2019,33(10):1915-1935
Modelling topological relationships between places and events is challenging especially because these relationships are dynamic, and their evolutionary analysis relies on the explanatory power of representing their interactions across different temporal resolutions. In this paper, we introduce the Space-Time Varying Graph (STVG) based on the whole graph approach that combines directed and bipartite subgraphs with a time-tree for representing the complex interaction between places and events across time. We demonstrate how the proposed STVG can be exploited to identify and extract evolutionary patterns of traffic accidents using graph metrics, ad-hoc graph queries and clustering algorithms. The results reveal evolutionary patterns that uncover the places with high incidence of accidents over different time resolutions, reveal the main reasons why the traffic accidents have occurred, and disclose evolving communities of densely connected traffic accidents over time. 相似文献
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该文阐述了零角坐标系的构成原理和实际运用 ,分析了零角坐标系图形展现的影响因素 ,从而为专题量化信息图形可视化提供了一种新的图形展现形式。 相似文献
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Long Zhang Nico Van de Weghe 《International journal of geographical information science》2018,32(5):1043-1059
Trajectory analysis has attracted growing attention in the research field of geography. Beyond traditional moving object trajectories, another type of trajectory exists in which the coordinates are object attributes rather than geographical coordinates. In this paper, a framework to analyse these so-called attribute trajectories is proposed that uses four techniques typically employed in the analysis of moving object trajectories: the Reeb graph, the similarity matrix, the convoy and the mega-convoy. The Reeb graph provides the ability to visualise the temporal dynamics of attribute similarities. The similarity matrix is a supplement of the Reeb graph whose purpose is to visualise the pairwise similarities among the attributes. Moreover, the similarity matrix forms a basis for clustering. The convoy highlights objects whose attributes remain similar for a sufficiently long period. The mega-convoy reduces the number of convoys and reveals their evolutionary histories by merging overlapping convoys. A small real-world meteorological dataset is used as an example to illustrate the attribute trajectory analysis framework and the techniques. This paper aims to form a starting point for applying trajectory analysis techniques in many research fields. 相似文献
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Force-directed layout of origin-destination flow maps 总被引：1，自引：0，他引：1
Bernhard Jenny Daniel M. Stephen Ian Muehlenhaus Brooke E. Marston Ritesh Sharma Eugene Zhang 《International journal of geographical information science》2017,31(8):1521-1540
This paper introduces a force-directed layout method for creating origin-destination flow maps. Design principles derived from manual cartography and automated graph drawing to increase readability of flow maps and graph layouts are taken into account. The origin-destination flow maps produced with our algorithm show flows with quadratic Bézier curves that reduce flow-on-flow and flow-on-node overlaps, and avoid sharp or irregular bends in flow lines. A survey of expert cartographers found that flow maps created with our automated method are similar in quality to manually produced flow maps. 相似文献
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基于图谱特征的中国典型城市空间结构演变分析 总被引：2，自引：1，他引：1
基于地学信息图谱的方法论,选取中国典型经济快速发展的城市,对中国典型城市空间结构演变的现状进行分析。结合不同时期城市空间结构的图谱,探索城市化与城市空间结构演变的影响因素。通过对城市空间结构特征的理解和测度来把握城市空间结构的演变,总结在城市化背景下城市空间结构演变的时空规律,为城市未来健康、协调、有序发展提供服务。研究结果表明: ①城市空间结构是城市的自然环境、经济、土地利用和城市交通等各种要素在空间组织分布形式和相互作用的过程。②城市化过程中人口大量向城市转移,对城市空间结构演变的影响总体呈扩增的趋势。③地形、河流港湾、人口和经济发展等是影响城市空间结构主要的因素。④良好的城市交通网络结构是城市得以正常运转的前提,城市经济快速发展离不开高效的交通网络系统;在城市交通的空间结构的扩展特征上显现出多种发展结构,如同心圆带状结构、扇形结构等。⑤ 在地形、水系等自然条件一定的情况下,城市的空间结构是由土地利用与城市交通网络在城市空间地域上相互制约和相互协调形成的。 相似文献
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ENRICO PUPPO PAOLA MARZANO 《International journal of geographical information science》2013,27(2):139-161
Many problems of practical interest involve line-of-sight on a topographic surface. Some such problems can be successfully studied on the basis of the mutual visibility among a finite number of representative points. Such visibility problems can be formalized and resolved as graph problems. In this paper, we show that graph algorithms can be useful to find efficient solutions for discrete visibility problems in several cases. On the basis of results from the theory of complexity, we give some practical rules to apply such an approach. We further investigate the solution of some relevant visibility problems under this perspective. 相似文献
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Yukio Sadahiro 《International journal of geographical information science》2013,27(7):997-1014
This paper proposes a method of analyzing spatial relations among point distributions on a discrete space. Spatial topology and proximity are discussed in an integrated framework at both local and global scales. Local relations are described by geographical representations, whereas global relations are visualized by graph representations. The latter also provide a means of classifying the point distributions. The proposed method is applied to school location planning in Japan. The results reveal the appealing properties of the method and provide empirical findings. 相似文献
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提出一种新的基于马尔可夫随机场(Markov Random Field,MRF)的图像分割算法。根据Gibbs分布与MRF的等价性,图像分割问题转换为后验能量函数最小化所对应的标号问题。该文采用图割技术的-αexpansion算法进行后验能量函数的局部最优化,并通过近似于最大期望(EM)算法的迭代过程估算数据模型中的参数。对合成图像和遥感图像的分割实验表明,该方法的运算时间和分割精度都能达到满意的效果。 相似文献
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A novel residual graph convolution deep learning model for short-term network-based traffic forecasting 总被引：1，自引：0，他引：1
Yang Zhang Tao Cheng Yibin Ren Kun Xie 《International journal of geographical information science》2020,34(5):969-995
ABSTRACT Short-term traffic forecasting on large street networks is significant in transportation and urban management, such as real-time route guidance and congestion alleviation. Nevertheless, it is very challenging to obtain high prediction accuracy with reasonable computational cost due to the complex spatial dependency on the traffic network and the time-varying traffic patterns. To address these issues, this paper develops a residual graph convolution long short-term memory (RGC-LSTM) model for spatial-temporal data forecasting considering the network topology. This model integrates a new graph convolution operator for spatial modelling on networks and a residual LSTM structure for temporal modelling considering multiple periodicities. The proposed model has few parameters, low computational complexity, and a fast convergence rate. The framework is evaluated on both the 10-min traffic speed data from Shanghai, China and the 5-min Caltrans Performance Measurement System (PeMS) traffic flow data. Experiments show the advantages of the proposed approach over various state-of-the-art baselines, as well as consistent performance across different datasets. 相似文献