首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
  相似文献   

2.
城市三维地理信息系统中三维模型的快速构建方法   总被引：2，自引：1，他引：2  
大规模三维模型的快速构建一直是影响城市三维地理信息系统(3DUGIS)发展的一个重要因素.基于3DUGIS中景观模型的表达原则与分类,分别针对抽象的点、线、面状对象提出符号匹配和三角剖分的批量三维模型构建方法.这种建模方法方便、快捷、自动化程度高,可广泛应用于城市景观中地面、河流、道路、绿地、规则建筑物、地下管线等地物的三维建模.通过对上述三维模型快速构建方法的实现,验证了三维模型生成的效果和效率.  相似文献   

3.
三维含拓扑地质剖面三角剖分可视化研究   总被引：1，自引：0，他引：1  
三维剖面是地质对象表达和地质问题分析中最基本和最常用的数据。该文分析三维复杂地质折剖面可视化存在的问题,并提出展开剖分算法。该方法保证了各点之间的水平距离与剖面拓扑关系不变,能够对由"多边形-弧段-结点"矢量结构构成的三维折剖面进行有效剖分。在此基础上实现了三维剖面的可视化,尤其合理解决了纹理映射中的纹理变形与重复接缝等问题。  相似文献   

4.
Polygonal vector data are important for representing countries, lakes, residential settlements, and other polygonal features. The proper representation of polygonal vector data is the basis of efficient rendering and picking and quick access and display of the analysis results based on polygons (e.g., 3D overlaying and surface area measurement in mountainous areas) in a virtual globe. However, polygonal vector data are displayed using texture-based or boundary-based approaches in most existing virtual globes. The texture-based approach cannot easily support interactive operations (e.g., picking) and spatial analysis (e.g., adjacency analysis and spatial measurement). The boundary-based approach treats the holes as independent features; however, it is difficult to recognize which boundaries constitute a polygon. Further research is needed on how to better organize the polygons to support efficient rendering, picking, and analysis in a virtual globe. In this article, we propose two methods to drape interior filled 2D polygons onto a multi-resolution 3D terrain. Both proposed methods combine polygon clipping and polygon triangulation. The difference between the two methods is in the way holes are eliminated. Method 1 recursively subdivides a terrain triangle until the child-triangles contain no holes; every resulting clipped polygon, which is then triangulated, contains no holes. Method 2 directly clips a polygon against a terrain triangle and creates bridge edges to transform the resulting polygons with holes to degenerate polygons that are further triangulated. The experimental results demonstrate that both proposed methods can efficiently process polygons with holes resulting in appropriate numbers of triangles. The processed interior-filled polygons remain close to the terrain surface in a virtual globe. Both proposed methods support real-time rendering of polygonal vector data in a virtual globe.  相似文献   

5.
面向GIS的矢量线状符号填充算法研究   总被引：3，自引：0，他引：3  
该文分析了GIS中矢量线状符号的特点与基本构成,提出了一种高效且通用的矢量线状符号的填充算法。该算法通过对构成矢量线状符号的几何图元进行旋转、变形、裁减等处理,可以实现对各种线状符号的填充,大大提高了算法的通用性和绘制效率。  相似文献   

6.
Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time.  相似文献   

7.
基于Web Geocoding的三维GIS快速定位方法研究   总被引：1，自引：0，他引：1  
三维GIS技术已经逐渐发展成熟,其对客观世界的表达能给人以更真实的感受,然而三维GIS软件所需数据是海量的。由于遥感技术的发展,纹理数据的获取和处理已经变得容易和快速,而对于矢量数据的采集、存储是一个非常艰巨的工作,如何在短期内获取海量、精确的矢量地理信息数据,减少数据采集的费用和时间成了一大难题。通过基于网络的地理编码来查询获取矢量点状地理信息,将地理信息存储到本地数据库,并且将数据应用到系统中进行快速定位显示,实现地理位置的实时定位和查询,为各种专题三维GIS软件开发提供服务和扩展功能。  相似文献   

8.
3DGIS中复合地形纹理生成与应用   总被引：1，自引：0，他引：1  
3DGIS仅用数字高程模型(DEM)表现地形远达不到三维可视化的要求.在传统3IDGIS中,通常采用数字正射影像(DOM)作为DEM的纹理表达地面景观,但其逼真性往往会受到影像分辨率的限制.该文借鉴Mipmap思想,提出一种新的纹理生成方法来解决上述问题,即通过对DOM和二维矢量数据赋予投影信息,将多幅影像及相关矢量数据作为生成3DGIS地形的纹理数据源,生成不同分辨率、不同详细程度的金字塔纹理,动态表现地面景观,并对生成的金字塔模型数据进行高效的索引、存储与管理.上述方法在实际应用中取得了满意的访问效率和视觉效果.  相似文献   

9.
体绘制技术在地学3D GIS 可视化中的应用研究   总被引：1，自引：0，他引：1  
体绘制技术是目前科学计算可视化研究的一个重要组成部分，对地质体内部属性分布的可视化有重要意义。该文针对地学研究中几何建模和属性建模同样重要的特点，基于一种矢栅一体化的混合数据模型，对地质体表面采用三角面片描述几何形状，对地质体内部采用基于八叉树的自适应网格剖分技术描述内部属性特征。对网格剖分后的体数据，采用体元投射的体绘制技术进行地质体内部属性可视化，显示出很好的效果，具有实际应用意义。  相似文献   

10.
Labeling plays an important role in map production, attaching specific texts to related geographic elements to provide clear environmental references. In three-dimensional geographical information systems (3DGISs), however, cluttering happens fairly commonly because of the unexpected overlapping and occlusion among labels and related objects, and results in an ambiguous and obscure environment. It generally also takes large computing power and memory to visualize spatial entities. Aimed at both unambiguous and efficient 3D map display, this article proposes an adaptive multi-resolution labeling method to deal with point, polyline, and polygon features labeling in a 3D landscape. It implements adaptive placement and view-driven label filtering without obscuring other visual features. The experiments indicated that the display of overlapping labels and label popping are reduced significantly with less computation burden while retaining the rendering quality.  相似文献   

11.
ABSTRACT

With large amounts of digital map archives becoming available, automatically extracting information from scanned historical maps is needed for many domains that require long-term historical geographic data. Convolutional Neural Networks (CNN) are powerful techniques that can be used for extracting locations of geographic features from scanned maps if sufficient representative training data are available. Existing spatial data can provide the approximate locations of corresponding geographic features in historical maps and thus be useful to annotate training data automatically. However, the feature representations, publication date, production scales, and spatial reference systems of contemporary vector data are typically very different from those of historical maps. Hence, such auxiliary data cannot be directly used for annotation of the precise locations of the features of interest in the scanned historical maps. This research introduces an automatic vector-to-raster alignment algorithm based on reinforcement learning to annotate precise locations of geographic features on scanned maps. This paper models the alignment problem using the reinforcement learning framework, which enables informed, efficient searches for matching features without pre-processing steps, such as extracting specific feature signatures (e.g. road intersections). The experimental results show that our algorithm can be applied to various features (roads, water lines, and railroads) and achieve high accuracy.  相似文献   

12.
The rise of Geographic Information Systems (GIS) technologies has been producing powerful tools for spatial data processing, management, analysis, modeling, and visualization. While supporting many tasks, GIS technologies have evoked new thinking and advanced intellectual inquiries in geography. Technological advances in other fields often stimulate new research questions and lead to revolutionary discoveries. The Hubble telescope revolutionizes our understanding of the universe, and 3D digital microscopes transform our knowledge of the coordination among biological, neurological, and physiological systems in living organisms. Can GIS claim similar revolutionary effects on geography? The answer is much up for debate. With GIS technologies, geographic studies can explore a broader extent across multiple scales in space and time and tackle problems through increasingly complex spatial statistics, visual analytics, computation, simulation, machine learning, and artificial intelligence. Both the Hubble telescope and 3D digital microscope were built based on scientific research that subserves the technological advances for inquiries into space and life systems. Likewise, GIScience research innovates GIS methods that enable novel geographic investigations and therefore contribute to geographic knowledge production. For the sake of simplicity, the term GIS used here represents both GIScience and GIS technologies. This essay attempts to clarify the intellectual contributions of GIS to geography on the following two questions: (1) What novel geographic thinking is driven by GIS? (2) How may GIS provoke new geographic inquiries and knowledge? Building on Nystuen's notion of four tensions that trigger geographic questions, the essay discusses how GIS innovations mediate historical tension, space‐time tension, dimensional tension and scale tensions.  相似文献   

13.
There has been a resurgence of interest in time geography studies due to emerging spatiotemporal big data in urban environments. However, the rapid increase in the volume, diversity, and intensity of spatiotemporal data poses a significant challenge with respect to the representation and computation of time geographic entities and relations in road networks. To address this challenge, a spatiotemporal data model is proposed in this article. The proposed spatiotemporal data model is based on a compressed linear reference (CLR) technique to transform network time geographic entities in three-dimensional (3D) (x, y, t) space to two-dimensional (2D) CLR space. Using the proposed spatiotemporal data model, network time geographic entities can be stored and managed in classical spatial databases. Efficient spatial operations and index structures can be directly utilized to implement spatiotemporal operations and queries for network time geographic entities in CLR space. To validate the proposed spatiotemporal data model, a prototype system is developed using existing 2D GIS techniques. A case study is performed using large-scale datasets of space-time paths and prisms. The case study indicates that the proposed spatiotemporal data model is effective and efficient for storing, managing, and querying large-scale datasets of network time geographic entities.  相似文献   

14.
提出GIS多边形倒金字塔模型,拓展了模型能够支持的数据结构与适用范围,使其可以应用于普通GIS电子地图中,为采用预生成不同比例尺图面多分辨率表达无极比例尺图形显示技术提供了模型支持,并给出了建模方法,使普通GIS多边形的无极比例尺显示可以依据精度标准进行局部更新和无冗余存储。  相似文献   

15.
The availability of continental and global-scale spatio-temporal geographical data sets and the requirement to efficiently process, analyse and manage them led to the development of the temporally enabled Geographic Resources Analysis Support System (GRASS GIS). We present the temporal framework that extends GRASS GIS with spatio-temporal capabilities. The framework provides comprehensive functionality to implement a full-featured temporal geographic information system (GIS) based on a combined field and object-based approach. A significantly improved snapshot approach is used to manage spatial fields of raster, three-dimensional raster and vector type in time. The resulting timestamped spatial fields are organised in spatio-temporal fields referred to as space-time data sets. Both types of fields are handled as objects in our framework. The spatio-temporal extent of the objects and related metadata is stored in relational databases, thus providing additional functionalities to perform SQL-based analysis. We present our combined field and object-based approach in detail and show the management, analysis and processing of spatio-temporal data sets with complex spatio-temporal topologies. A key feature is the hierarchical processing of spatio-temporal data ranging from topological analysis of spatio-temporal fields over boolean operations on spatio-temporal extents, to single pixel, voxel and vector feature access. The linear scalability of our approach is demonstrated by handling up to 1,000,000 raster layers in a single space-time data set. We provide several code examples to show the capabilities of the GRASS GIS Temporal Framework and present the spatio-temporal intersection of trajectory data which demonstrates the object-based ability of our framework.  相似文献   

16.
孙仲明 《地理研究》1982,1(1):86-93
在河北省平山县战国中山国都城遗址以西约2公里的一座大型中山王中山王中山王墓(一号墓)的发掘中,发现一幅刻划在一块长94厘米、宽48厘米、厚约1厘米的长方形铜版上的地图——《兆域图》[1](见附图),在这幅图上标有“中宫垣”、内宫垣”、“丘足”、“宫”、“堂”、“门”等图形线划符号、数字注记和文字说明;图上还刻有中山王命四十三字。图形线划之间注有距离数据。线条、符号与铭文都用金银镶错而成,是一幅制作极为精细、极为完整的墓域建筑规划平面图。  相似文献   

17.
地理时空三向聚类分析方法的构建与实践   总被引：1，自引：0，他引：1  
随着地理数据获取能力的不断提升,地理数据体量呈指数增长,数据种类、数据性质更加多元化。对数据的有效甄别和归类成为理解地理现象时空特征、演化过程和行为机制的关键。传统聚类方法面临数据体量大、维数高、质量差的挑战,加之对地理空间与时间关联分析的需求,对聚类方法改进和提升研究的要求越来越迫切。本文介绍了从单向到三向聚类构建思路的变革。单向聚类是仅在样本或属性方向上进行聚类,易忽视非常相似的局部特征、易犯“横看成岭侧成峰”的错误。双向聚类是基于数据矩阵内元素值的相似性,形成一个子矩阵分割方案,使子矩阵内元素相似度尽可能高,子矩阵间元素相似度尽可能低,从而实现行列两方向的同时聚类,避免了单向聚类的不足。鉴于双向聚类难以满足地理研究超出双向的解译需求,本文提出并研发了一个全新的三向聚类方法,给出了运用该方法开展地理时空格局过程探测的流程,总结了如何根据研究涉及的“空间—时间—尺度—属性”构建三维数据体;最后,展示了三向聚类的地理实践案例。结果表明：① 三向聚类是一种大数据时代探测地理数据时空分异规律的有效方法,可以解决数据维度高、质量低等问题;② 面对不同的地理问题,三向聚类在算法层面上是通用的,不同之处仅在于：根据不同问题涉及的空间、时间、尺度、属性的不同,构建不同的数据体;不同数据体聚类得到的不同结果回答不同的地理问题;③ 三向聚类可以实现地理数据的时空分异规律多方向、多尺度、多层次的联合解译,揭示地理特征时空尺度叠加效应。最后,论文强调根据地理问题组织数据的重要性,期待未来能够提升三向聚类在多空间尺度、多属性方面的地理研究实践。  相似文献   

18.
Wildfire evacuation trigger points are prominent geographic features (e.g., ridge lines, rivers, and roads) utilized in timing evacuation warnings. When a fire crosses a feature, an evacuation warning is issued to the communities or firefighters in the path of the fire. Current methods for generating trigger buffers have limited utility because the resulting buffers are not explicitly tied to prominent geographic features, making it difficult to visually determine when a fire has breached a trigger point. This work aims to address this limitation by using reverse geocoding to identify prominent geographic trigger points that have more value to emergency managers. The method consists of three steps: 1) generate a trigger buffer using fire-spread modeling; 2) utilize online reverse-geocoding to retrieve geographic features proximal to the buffer boundary; and 3) identify the most prominent geographic features using viewshed analysis and compute the warning time each would offer given predicted fire spread rates to proximal communities. A case study of Julian, California is presented to identify prominent geographic trigger points that may have value to emergency managers in improving the timing of wildfire evacuation warnings in this region.  相似文献   

19.
为实现大规模地形的多分辨率显示与实时绘制,基于LOD技术给出了多尺度TIN的管理和表达算法。探讨该算法相关的数据组织、LOD层次表达、实时刷新等关键问题。该算法使用分级策略,在不影响视觉效果前提下对TIN进行分级表达;使用分区策略,在可视化过程中对TIN进行局部更新。采取不同分辨率TIN模型间逐步过渡策略,基本上消除了视图变换时的跳跃感。实验结果表明,这种紧凑有效的TIN表示方法实现简单,内存开销较少,CPU耗费小,大大缩短了视图刷新切换时间,能够在普通机器上实现大规模地形的实时漫游。  相似文献   

20.
The integration of Building Information Modelling (BIM) and geographic information systems (GIS) is a promising but challenging topic to solve problems in construction industry. However, loading and rendering rich BIM geometric data and large-scale GIS spatial information in a unified system is still technologically challenging. Current efforts mainly simplify the geometry in BIM models, or convert BIM geometric data to a lower level of detail (LOD). By noticing that only exterior features of BIM models are visible from outdoor observation points, culling BIM interior facilities can dramatically reduce the computational burden when visualizing BIM models in GIS. This study explores the outline detection problem and presents the OutDet algorithm, which selects representative observation points, transforms & projects the BIM geometric data into the same coordinate system, and detects the visible facilities. Empirical study results show that OutDet can cull a large portion of unnecessary features when rendering BIM models in GIS. The use of outlines of BIM models is not an alternative but rather a supplementary approach for current solutions. Jointly using LOD and outer surface can help improve the efficiency of integrated BIM-GIS visualization.Because OutDet retains BIM geometry and semantics, it can be applied to more BIM-GIS applications..  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号