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1.
Qualitative knowledge representation of spatial locations and relations is popular in many text-based media, for example, postings on social networks, news reports, and encyclopedia, as representing qualitative spatial locations is indispensable to infer spatial knowledge from them. However, an integrative model capable of handling direction-based locations of various spatial objects is missing. This study presents an integrative representation and inference framework about direction-based qualitative locations for points, lines, and polygons. In the framework, direction partitions of different types of reference objects are first unified to create a partition consisting of cells, segments, and corners. They serve as a frame of reference to locate spatial objects (e.g., points, lines, and polygons). Qualitative relations are then defined to relate spatial objects to the elements in a cell partition, and to form the model of qualitative locations. Last, based on the integrative representation, location-based reasoning mechanism is presented to derive topological relations between objects from their locations, such as point–point, line–line, point–line, point–polygon, line–polygon, and polygon–polygon relations. The presented model can locate any type of spatial objects in a frame of reference composed of points, lines, and polygons, and derive topological relations between any pairs of objects from the locations in a unified method.  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.
Matching road networks is an essential step for data enrichment and data quality assessment, among other processes. Conventionally, road networks from two datasets are matched using a line-based approach that checks for the similarity of properties of line segments. In this article, a polygon-based approach is proposed to match the OpenStreetMap road network with authority data. The algorithm first extracts urban blocks that are central elements of urban planning and are represented by polygons surrounded by their surrounding streets, and it then assigns road lines to edges of urban blocks by checking their topologies. In the matching process, polygons of urban blocks are matched in the first step by checking for overlapping areas. In the second step, edges of a matched urban block pair are further matched with each other. Road lines that are assigned to the same matched pair of urban block edges are then matched with each other. The computational cost is substantially reduced because the proposed approach matches polygons instead of road lines, and thus, the process of matching is accelerated. Experiments on Heidelberg and Shanghai datasets show that the proposed approach achieves good and robust matching results, with a precision higher than 96% and a F1-score better than 90%.  相似文献   

4.
Studies of land-use change often require the combination of socioeconomic survey data with spatially continuous maps of land-cover change. One approach is to define maps of land ownership, assuming that all land-use change can be attributed to the owners or managers of each parcel of land. Unfortunately, records of administrative boundaries between towns and villages are commonly unavailable in developing countries and prohibitively costly or time consuming to map for individual projects. However, point locations of the settlements themselves can be obtained easily from existing maps or remotely-sensed imagery. In this paper we compare three methods – circular buffers, unweighted Voronoi polygons (sometimes referred to as Thiessen polygons) and multiplicatively weighted Voronoi polygons – for estimating boundaries between villages in an agricultural landscape in West Africa. The benefits and limitations of each approach are discussed, and their accuracy assessed using 98 independently collected GPS coordinates of village boundaries. We present a novel method for generating and optimising weights for multiplicatively weighted Voronoi polygons using survey data of village sizes from a subset of villages. By using both spatial information and survey data from villages, we show that multiplicatively weighted Voronoi polygons outperform other methods of predicting village boundaries, and increase the correlation coefficient between surveyed village area and mapped areas from 0.18 to 0.68 compared with more commonly used unweighted Voronoi polygons. Our method of weighting Voronoi polygons can be implemented with data and software commonly available to researchers and non-governmental organisations.  相似文献   

5.
Fire history studies have traditionally emphasized temporal rather than spatial properties of paleo‐fire regimes. In this study we compare four methods of mapping paleo‐fires in central Washington from binary point data: indicator kriging, inverse distance weighting, Thiessen polygons, and an expert approach. We evaluate the results of each mapping method using a test (validation) dataset and receiver operating characteristic plots. Interpolation methods perform well, but results vary with fire size and spatial pattern of points. Though all methods involve some subjectivity, automated interpolation methods perform well, are replicable, and can be applied across varying landscapes.  相似文献   

6.
Location siting is an important part of service provision, with much potential to impact operational efficiency, safety, security, system reliability, etc. A class of location models seeks to optimize coverage of demand for service that is continuously distributed across space. Decision-making and planning contexts include police/fire resource allocation for a community, siting cellular towers to support cell phone signal transmission, locating emergency warning sirens to alert the public of severe weather and other related dangers, and many others as well. When facilities can be sited anywhere in continuous space to provide coverage to an entire region, this is a very computationally challenging problem to solve because potential demand for service is everywhere and there are an infinite number of potential facility sites to consider. This article develops a new parallel solution approach for this location coverage optimization problem through an iterative bounding scheme on multi-core architectures. The developed approach is applied to site emergency warning sirens in Dublin, Ohio, and fire stations in Elk Grove, California. Results demonstrate the effectiveness and efficiency of the proposed approach, enabling real-time analysis and planning. This work illustrates that the integration of cyberinfrastructure can significantly improve computational efficiency in solving challenging spatial optimization problems, fitting the themes of this special issue: cyberinfrastructure, GIS, and spatial optimization.  相似文献   

7.
An algorithm was developed for converting radar data from matrix format into polygons that can be easily visualized, processed, and analyzed using Geographic Information Systems. Spatial operators can be used to overlap radar polygons with land surface features represented by points, lines, and polygons to meet the demands of severe weather identification and tracking and risk recognition. Application and testing of the algorithm demonstrate that the converted radar polygons are suitable for use in weather modification, risk assessments of flash floods in urban areas, and the identification of lightning activity for lightning risk recognition, all of which are essential in real-time severe weather monitoring and warning.  相似文献   

8.
Visibility computation on terrain models is an important research topic with many applications in Geographical Information Systems. A multi‐visibility map is the subdivision of the domain of a terrain into regions that, according to different criteria, encodes the visibility with respect to a set of view elements. We present an approach for visualising approximated multi‐visibility maps of a triangulated terrain corresponding to a set of view elements by using graphics hardware. Our method supports heterogeneous sets of view elements containing points, segments, polygonal chains and polygons and works for weak and strong visibility. Moreover, we are also able to efficiently solve approximated point and polygonal region multi‐visibility queries. To illustrate the usefulness of our approach we present results obtained with an implementation of the proposed algorithms.  相似文献   

9.
中国省级人口增长率及其空间关联分析   总被引：38，自引：0，他引：38  
分析了1982－1990年和1990－1998年2个时期的人口增长率，并用空间统计分析方法研究了2个时期人口增长率的空间关联关系。1982－1990年中国可分为北部人口低增长、中西部高人口增长率、中东部低人口增长率和南部高人口增长率等4个区域，1990－1998年中国可分为北部低人口增长率和南部高人口增长率2个区域，2个时期的空间聚类虽然不完全相同，但它们有共同的特点，南部和西部的人口增长率都比较高，北部地区的人口增长率都比较低，但它们有共同的特点，南部和西部的人口增长率都比较高，北部地区的人口增长率都比较低。最后对实证研究的结果进行了分析。  相似文献   

10.
Public service systems, such as emergency health care, police or fire brigades, are critical for day-to-day functioning of the society. To design and operate these systems efficiently much data needs to be collected and properly utilised. Here, we use the OpenStreetMap (OSM) data to model the demand points (DPs), which approximate the geographical location of customers, and the road network, which is used to access or distribute services. We consider all inhabitants as customers, and therefore to estimate the demand, we use the available population grids. People are changing their location in the course of the day and thus the demand for services is changing accordingly. In this paper, we investigate how the used demand estimate affects the optimal design of a public service system. We calculate and compare efficient designs corresponding to two demand models, a night-time demand model when the majority of inhabitants rest at home and the demand model derived from the 24-hour average of the population density. We propose a simple measure to quantify the differences between population grids and we estimate how the size of differences affects the optimal structure of a public service system. Our analyses reveal that the efficiency of the service system is not only dependent on the placement strategy, but an inappropriate demand model has significant effects when designing a system as well as when evaluating its efficiency.  相似文献   

11.
区域城镇空间格局的识别方法及案例分析   总被引：2，自引：1，他引：1  
通过分析城镇之间的空间关系,探讨了区域城镇空间格局的定量化识别方法。该方法包含3个步骤：一是通过人口、产业或交通优势度的分析,识别具有较大发展潜力的城市、城镇或城镇集聚区（空间节点）。二是以空间节点之间的交通联系及其未来发展变化情况为依据,利用多维尺度分析方法展现城镇之间的空间关系（空间联系）。三是确定城镇空间影响范围,进而确定城镇空间体系的整体架构（空间圈域）。以广西西江流域7个地级市为例,运用该方法,分析了2000年以来广西西江黄金水道及区域性综合交通体系的建设对区域城镇体系产生的影响,对未来城镇空间格局的变化进行了预测。  相似文献   

12.
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   

13.
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14.
The paper discusses an approach known as ‘distance‐decayed visibility’, implemented using GIS, to the composition of 3D scenes for static forest landscape visualization. The distance‐decay concept is employed to model a spatial interaction in terms of visibility between any observation points and vegetations visible from those points. The vegetation visibility is measured in level of detail where high visibility uses high level of detail and vice versa. The interaction is modelled mathematically using an exponential decay function. The point distribution of projected models on a 3D scene is calculated in GIS to assign an appropriate value of ‘visibility decay constant’ to relate the distance from the observation point to the vegetations with the level of detail of the vegetations in the function. The advantages of the technique as measured against the quantitative benchmarks of rendering time and the number of polygons computed are addressed. Although the forest landscape of the study area consists of a large number of vegetation models, the technique helps to model the relation of vegetation visibility and viewing distance so realistically that the technique yields the visual quality of the result 3D scene visually and statistically comparable to the finest resolution scene.  相似文献   

15.
A spatial modeling technique is proposed to represent boundary uncertainty or gradation on area-class maps using a simple polygon tessellation with designated zones of indeterminacy or transition zones. The transition zone can be conceptualized as a dual of the epsilon band, but is more flexible and allows for a wide range of polygonal configurations, including polygons with sinuous boundaries, spurs, three-way transition zones, and null polygons. The model is specified using the medial axis to capture the general shape characteristics of a transition zone. Graph theoretic representation of an extended version of the medial axis captures key junctions in both shape and classification and is used to identify well-formed transition zones that can be logically and unambiguously handled by the model. A multivariate classification surface is specified by first defining degrees or probabilities of membership at every point on the medial axis and transition zone boundary. Degrees or probabilities of membership at all other points are defined by linear interpolation. The technique is illustrated with an example of a complex transition zone, and a simple isoline representation that can be derived from the model is presented. The proposed modeling technique promises to facilitate expert characterization of soil formations, ecological systems, and other types of areal units where gradation and/or boundary uncertainty are prevalent.  相似文献   

16.
Many landscape features are represented as polygons in GIS. This paper characterizes polygon shapes with the multiplicatively weighted Voronoi (MW‐Voronoi) diagram and improves its understanding. The MW‐Voronoi diagram's composition is implemented with topological overlay, growth simulation, and vertex calculation methods. The decomposition is done by reversing a polygon to MW‐Voronoi point pairs by segment. It is a new approach to record, characterize, and compare polygons with form and process. The implementation also serves as a geographic education and visualization tool. Applications of the methods are presented with precipitation, fire polygon, and population change data.  相似文献   

17.
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18.
中国数字地貌分层分类体系的结构和内容研究(英文)   总被引：9，自引：2，他引：7  
This paper presents the structure and contents of a standardized layered classification system of digital geomorphology for China.This digital classification method combines landforms characteristics of morphology with genesis.A total of 15 categories of exogenic and endogenic forces are divided into two broad categories:morpho-genetic and morpho-structural landforms.Polygon patches are used to manage the morpho-genetic types,and solitary points,lines and polygons are used to manage the morpho-structural types.The classification method of digital morpho-genetic types can be divided into seven layers,i.e.basic morphology and altitude,genesis,sub-genesis,morphology,micro-morphology,slope and aspect,material and lithology.The method proposes combinations of matrix forms based on layered indicators.The attributes of every landform types are obtained from all or some of the seven layers.For the 15 forces categories,some classification indicators and calculation methods are presented for the basic morphology,the morphologic and sub-morphologic landforms of the morpho-genetic types.The solitary polygon,linear and point types of morpho-structural landforms are presented respectively.The layered classification method can meet the demands of scale-span geomorphologic mapping for the national primary scales from 1:500,000 to 1:1,000,000.The layers serve as classification indicators,and therefore can be added and reduced according to mapping demands,providing flexible expandability.  相似文献   

19.
Several algorithms have been proposed to generate a polygonal ‘footprint’ to characterize the shape of a set of points in the plane. One widely used type of footprint is the χ-shape. Based on the Delaunay triangulation (DT), χ-shapes guaranteed to be simple (Jordan) polygons. This paper presents for the first time an incremental χ-shape algorithm, capable of processing point data streams. Our incremental χ-shape algorithm allows both insertion and deletion operations, and can handle streaming individual points and multiple point sets. The experimental results demonstrated that the incremental algorithm is significantly more efficient than the existing, batch χ-shape algorithm for processing a wide variety of point data streams.  相似文献   

20.
简单要素模型下多边形叠置分析算法   总被引：1，自引：0，他引：1  
现有的矢量空间叠置分析多采用拓扑模型,要求建立完整的数据拓扑关系。该文采用简单要素模型,以多边形叠置交运算为例,介绍简单要素模型下空间叠置分析的具体实现,着重讨论多边形交运算的交替搜索算法,在线段求交中对连续出入点、重交点等特殊数据进行处理。在实际应用中,该算法可较好解决大规模复杂数据层的叠置交运算,比同规模的拓扑叠置运算效率高。  相似文献   

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