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This paper explains why it is vital to account for uncertainty when utilising socioeco‐nomic data in a GIS, focusing on a novel and intuitive method to visually represent the uncertainty. In common with other data, it is not possible to know exactly how far from the truth socioeconomic data are. Therefore, when such data are used in a decision‐making environment an approximate measure given for correctness of data is an essential component. This is illustrated, using choropleth mapping techniques on census data as an example. Both attribute and spatial uncertainty are considered, with Monte Carlo statistical simulations being used to model attribute uncertainty. An appropriate visualisation technique to manage certain choropleth issues and uncer‐tainty in census type data is introduced, catering for attribute and spatial uncertainty simultaneously. This is done using the output from hierarchical spatial data structures, in particular the region quadtree and the HoR (Hexagon or Rhombus) quadtree. The variable cell size of these structures expresses uncertainty, with larger cell size indicating large uncertainty, and vice versa. This technique is illustrated using the New Zealand 2001 census data, and the TRUST (The Representation of Uncertainty using Scale‐unspecific Tessellations) software suite, designed to show spatial and attribute uncertainty whilst simultaneously displaying the original data. 相似文献
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为满足海量地铁隧道点云的高效处理需求,提出了一种R树与格网结合的海量地铁隧道点云管理方法。针对隧道点云的空间分布特点,在全局将大范围点云划分到格网中,并使用R树管理非空网格;在局部使用八叉树与四叉树混合的索引方法管理单个网格内的点云。为了提高点云的渲染效果,提出了基于网格面积的多细节层次结构（levels of detail,LOD）回溯构建方法,并采用高效的单文件存储方式存储点云。实验结果证明了所提出的方法在海量隧道点云的管理和可视化方面优于传统方法。 相似文献
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Land managers responsible for invasive species removal in the USA require tools to prevent the Asian longhorned beetle (Anoplophora glabripennis) (ALB) from decimating the maple-dominant hardwood forests of Massachusetts and New England. Species distribution models (SDMs) and spread models have been applied individually to predict the invasion distribution and rate of spread, but the combination of both models can increase the accuracy of predictions of species spread over time when habitat suitability is heterogeneous across landscapes. First, a SDM was fit to 2008 ALB presence-only locations. Then, a stratified spread model was generated to measure the probability of spread due to natural and human causes. Finally, the SDM and spread models were combined to evaluate the risk of ALB spread in Central Massachusetts in 2008–2009. The SDM predicted many urban locations in Central Massachusetts as having suitable environments for species establishment. The combined model shows the greatest risk of spread and establishment in suitable locations immediately surrounding the epicentre of the ALB outbreak in Northern Worcester with lower risk areas in suitable locations only accessible through long-range dispersal from access to human transportation networks. The risk map achieved an accuracy of 67% using 2009 ALB locations for model validation. This model framework can effectively provide risk managers with valuable information concerning the timing and spatial extent of spread/establishment risk of ALB and potential strategies needed for effective future risk management efforts. 相似文献
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结合空间数据库、GIS、计算机图形学、RS等技术构建了虚拟现实地理信息系统。通过研究地形数据的生成及空间数据库的存储管理,实现了遥感影像的自动配准及无缝拼接;基于四叉树的LOD算法、地形节点评价系统、动态调度及大规模纹理映射等技术的研究,实现了地形数据的3维可视化;提出了自适应特征数据覆盖渲染算法,将2维GIS特征数据覆盖叠加到所创建的3维模型上,构建了虚拟现实环境。该系统成功应用于胜利油田,实现了地下油田的虚拟现实3维可视化,具有一定的理论价值和现实意义。 相似文献
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M-Quadtree索引:一种基于改进四叉树编码方法的云存储环境下空间索引方法 总被引：1，自引：0，他引：1
为了解决基于"键-值"模型的云存储环境仅支持简单的关键字查询,不支持多维空间查询的问题,提出了一种新的分布式空间索引方法——M-Quadtree索引。在索引构建过程中,设计了一种基于改进四叉树的空间数据划分方法,该方法规定了叶节点区域的最小数据量,通过四叉树叶节点的再合并,解决了划分后各子区域间存储量不平衡的问题,并且满足了MapReduce并行化要求。给出了MapReduce框架下M-Quadtree索引的快速构建、查询与更新算法,并在搭建的Hadoop平台进行了关键参数对索引效率的影响以及不同规模数据下索引的创建、查询和更新试验。与现有分布式空间索引的对比试验及分析结果表明,M-Quadtree索引在数据存储量负载均衡、算法并行化和空间查询效率等方面表现得更好。 相似文献
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基于线性四叉树的全球离散格网索引 总被引：8，自引：0，他引：8
将四元三角剖分的三角形格网组织成四叉树剖分的菱形块格网,以菱形块单元来进行数据的组织索引,通过线性四叉树成熟的Morton编码作为关键字来标识查找菱形块,并在此基础上经过改进来索引三角形格网、进行邻域搜索。 相似文献
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A Framework for Modeling Uncertainty in Spatial Databases 总被引：1，自引：0，他引：1
A Morris 《Transactions in GIS》2003,7(1):83-101
Geographic Information Systems and spatial databases are inherently suited for fuzziness, because of the uncertainty inherent in the assimilation, storage, and representation of spatial data. These objects may also have naturally occurring imprecise boundaries. It is difficult to store and represent these objects while continuing to demonstrate the uncertainty inherent in the objects. This paper describes a fuzzy object–oriented framework to model spatial objects with either precise or uncertain boundaries that will also provide for fuzzy querying of these objects. A prototype system, FOOSBALL, which implements this framework is also discussed. 相似文献
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MODIS数据存储格式研究 总被引：1，自引：0，他引：1
新型的遥感数据MODIS在近年来得到了比较广泛的应用,该数据有很多优点,在地理科学与资源管理中的应用潜力很大。深入研究该数据采用的HDF文件的数据结构,是开发自主知识产权的遥感图像处理软件的前提工作。本文就:什么是HDF,为什么创造HDF,HDF的高等级应用程序接口,HDF命令行用法和可视化工具,主要的HDF平台,HDF的基本原理,HDF文件格式,用多文件接口对HDF文件的基本操作,确定一个文件是否为HDF文件等问题展开了讨论。 相似文献
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In this study, an uncertainty analysis procedure for joint sequential simulation of multiple attributes of spatially explicit models used in geographical informational systems was developed based on regression analysis. This procedure utilizes information obtained from joint sequential simulation to establish the relationship between model uncertainty and variation of model inputs. Using this procedure, model variance can be partitioned by model input parameters on a cell by cell basis. In the partitioning, the correlation of neighboring cells is accounted for. With traditional uncertainty analysis methods, this is not possible. In a case study, spatial variation of soil erodibility from a joint sequential simulation of soil properties was analyzed. The results showed that the regression approach is a very effective method in the analysis of the relationship between variation of the model output and model input parameters. It was also shown for the case study that: (1) the uncertainty of soil erodibility of a cell is mainly propagated from its own soil properties; (2) the interactions of soil properties of neighboring cells could reduce uncertainty of soil erodibility; (3) it is sufficient for uncertainty analysis to include the nearest three neighboring cell groups; and (4) the largest uncertainty contributors vary by soil properties and location. 相似文献
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The repair of terrain cracks is an important process in multi‐resolution three‐dimensional terrain visualization, and rapid and accurate pinpointing of cracks between terrain blocks is of the utmost importance for this process. The existing quadtree‐based crack locating methods are generally slow and inefficient, as they require the traversal of terrain quadtrees to locate terrain cracks. In this research, we propose a fast quadtree‐based terrain crack locating method that accounts for adjacency information. First, terrain quadtrees are constructed that contain information regarding adjacency relationships. Second, dynamic updating is performed for terrain quadtrees and their adjacency information. Finally, terrain cracks are located by using the adjacencies of the quadtree nodes. This proposed method was experimentally validated via the terrain data of a mountainous region in Sichuan Province. The experimental results indicate that the proposed method can be used to efficiently and accurately locate terrain cracks with a strong performance in practical applications. 相似文献
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为了实现全球多分辨率地形快速、高效模拟与可视化表达,本文探讨了基于球面退化四叉树的全球多分辨率DEM无缝建模方法,主要内容包括：提出了一种基于球面退化四叉树的全球DEM分块建模方法;设计并实现了四叉树块内（相邻节点间相差任意剖分层次）、四叉树块间、四叉树与非四叉树块间的自适应无缝拼接算法;应用VC++语言和OpenGL工具,设计开发了相应的可视化实验系统,结果表明：该模型方法实现了全球多分辨率DEM的无缝表达,并在保证精度的同时有效简化了全球DEM格网的数目,简化效率为66.8%（剖分层次为12）。 相似文献
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针对当前地形三维可视化技术的研究现状,在吸取计算机图形学、虚拟现实、地理信息学、现代数学的先进理论和技术成果的基础上,根据地形表面平坦程度不同对原始地形模型预简化,对表面较平坦的区域不再分层,将原始地形模型的完全四叉树结构改变成自适应四叉树结构,从而生成自适应四叉树结构的地形模型,并采用VC^＋＋结合OpenGL加以实现。 相似文献
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本文对电子政务和数字中国地理空间基础框架的基本概念、内容和体系结构进行深入分析,指出电子政务与地理基础空间数据框架的关系非常密切,并强调说明:电子政务需要数字中国地理空间基础框架的支撑,集中体现在:数字中国地理空间基础框架是电子政务的空间定位平台,可以为电子政务提供空间辅助决策支持,并可为电子政务提供清晰易读的可视化工具;与此同时,电子政务为数字中国地理空间基础框架的建设提供了新的应用空间和发展机遇。 相似文献
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地质领域数据量大,且种类多样。实现高效的多源异构地质数据的融合与挖掘,是研究地质作用机理,展开地质考察研究的重要手段。然而目前普遍存在着数据条块分割,格式各异,难以实现有效的共享与互操作。为此,本文提出了一种基于Hadoop的地质大数据融合与挖掘技术框架,该框架包括统一的地质大数据采集与预处理方法,基于元数据索引的存储与管理平台,基于Map/Reduce的地质大数据并行化计算模式与系统,面向可重用的地质大数据挖掘服务,以及支持在线三维展示的地质大数据分析结果可视化系统。该框架具有良好的实用性与可扩展性。本文在5个节点的测试系统上实现了多元素关联性分析,并取得了相对应单台机器3部的加速可比性。 相似文献
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《制图学和地理信息科学》2013,40(3):139-160
Developing reliable methods for representing and managing information uncertainty remains a persistent and relevant challenge to GIScience. Information uncertainty is an intricate idea, and recent examinations of this concept have generated many perspectives on its representation and visualization, with perspectives emerging from a wide range of disciplines and application contexts. In this paper, we review and assess progress toward visual tools and methods to help analysts manage and understand information uncertainty. Specifically, we report on efforts to conceptualize uncertainty, decision making with uncertainty, frameworks for representing uncertainty, visual representation and user control of displays of information uncertainty, and evaluative efforts to assess the use and usability of visual displays of uncertainty. We conclude by identifying seven key research challenges in visualizing information uncertainty, particularly as it applies to decision making and analysis. 相似文献