共查询到20条相似文献，搜索用时 15 毫秒
1.
Oliver Gunther Philippe Picouet Jean-Marc Saglio Michel Scholl Vincent Oria 《International journal of geographical information science》2013,27(7):639-655
Spatial joins are join operations that involve spatial data types and operators. Spatial access methods are often used to speed up the computation of spatial joins. This paper addresses the issue of benchmarking spatial join operations. For this purpose, we first present a WWW-based benchmark generator to produce sets of rectangles. Using a Web browser, experimenters can specify the number of rectangles in a sample, as well as the statistical distributions of their sizes, shapes, and locations. Second, using the generator and a well-defined set of statistical models we define several tests to compare the performance of three spatial join algorithms: nested loop, scan-and-index, and synchronized tree traversal. We also added two real-life data sets from the Sequoia 2000 storage benchmark. Our results show that the relative performance of the different techniques mainly depends on the selectivity factor of the join predicate. All of the statistical models and algorithms are available on the Web, which allows for easy verification and modification of our experiments. 相似文献
2.
Jing Gao James E. Burt A-Xing Zhu 《International journal of geographical information science》2013,27(10):1959-1978
Raster-based slope estimation is routine in GIS. Like many other terrain attributes, the slope at a location is determined from elevations of surrounding cells. This spatial extent – ‘neighborhood size’ – is often treated as the ‘spatial scale’ of the calculation. In fact, neighborhood size and spatial scale are two connected yet different concepts, but few studies have investigated the relationship between them. The distinction is important because neighborhood size is under user control whereas spatial scale is merely implicit in the computational method. This article attempts to clarify and provide a more precise meaning of the two terms by considering slope operators from the standpoint of the frequency (or wavenumber) domain. This article derives analytical expressions for the amplitude response functions of four popular slope estimators. These are used to characterize the individual methods and also to show that the neighborhood size and spatial scale of a slope calculation are not numerically the same. In fact, because there is no single spatial scale that can be unambiguously associated with a given neighborhood size, neighborhood size cannot be an adequate indicator of spatial scale. Furthermore, this article shows that different indices of ‘scale’ yield different impressions about the action of a slope estimator and its response to changing neighborhood size. Therefore, it is necessary to examine the amplitude response function when investigating the spatial scale. The article also provides guidance for GIS practitioners when selecting a slope estimation method. 相似文献
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Haosheng Huang Yan Li Georg Gartner 《International journal of geographical information science》2013,27(10):1561-1574
XML/GML/SVG-based approaches are promising for building Web-based geographic information systems (WebGIS). However, current XML/GML/SVG-based WebGISs are lacking in spatial analysis. Some of them are designed for web mapping only. Others adopt a server-side solution for spatial analysis, which suffers from the ‘bottleneck’ problem and results in a high network transmission load. Load-balancing spatial analysis between server side and browser side can be used to solve the above problems. This article focuses on one of the key building blocks of load-balancing spatial analysis, that is, SVG-based spatial analysis which enables spatial querying and analysis directly on SVG (on the browser side). After analyzing the workflow of spatial analysis, we identify and focus on two key issues in providing spatial analysis on SVG: SVG-based spatial information representation and SVG-based spatial extended structured query language (SSESQL). For the first issue, a theoretical foundation is set up to develop an SVG-based spatial information representation model. Some spatial operators are designed and integrated into an SSESQL to support spatial querying on SVG. Finally, we design and implement two case studies. The results of these case studies show that the proposed method is feasible and operable in supporting spatial analysis directly on SVG on the browser side. The proposed method can be easily incorporated with some existing methods (e.g., GML-based spatial analysis on the server side) to provide load-balancing spatial analysis (load balancing between server side and browser side) in XML/GML/SVG-based WebGIS. As a result, users can access high-performance spatial analysis simply via a web browser (such as Internet Explorer and Firefox). 相似文献
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Farhana Jabeen Alvaro A.A. Fernandes 《International journal of geographical information science》2013,27(4):815-844
Existing sensor network query processors (SNQPs) have demonstrated that in-network processing is an effective and efficient means of interacting with wireless sensor networks (WSNs) for data collection tasks. Inspired by these findings, this article investigates the question as to whether spatial analysis over WSNs can be built upon established distributed query processing techniques, but, here, emphasis is on the spatial aspects of sensed data, which are not adequately addressed in the existing SNQPs. By spatial analysis, we mean the ability to detect topological relationships between spatially referenced entities (e.g. whether mist intersects a vineyard or is disjoint from it) and to derive representations grounded on such relationships (e.g. the geometrical extent of that part of a vineyard that is covered by mist). To support the efficient representation, querying and manipulation of spatial data, we use an algebraic approach. We revisit a previously proposed centralized spatial algebra comprising a set of spatial data types and a comprehensive collection of operations. We have redefined and re-conceptualized the algebra for distributed evaluation and shown that it can be efficiently implemented for in-network execution. This article provides rigorous, formal definitions of the spatial data types, points, lines and regions, together with spatial-valued and topological operations over them. The article shows how the algebra can be used to characterize complex and expressive topological relationships between spatial entities and spatial phenomena that, due to their dynamic, evolving nature, cannot be represented a priori. 相似文献
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Abstract Spatial join indices are join indices constructed for spatial objects. Similar to join indices in relational database systems, spatial join indices improve efficiency of spatial join operations. In this paper, a spatial-information-associated join indexing mechanism is developed to speed up spatial queries, especially, spatial range queries. Three distance-associated join index structures: basic, ring-structured and hierarchical, are developed and studied. Such join indexing structures can be further extended to include orientation information for flexible applications, which leads to zone-structured and other spatial-information-associated join indices. Our performance study and analysis show that spatial-information-associated join indices substantially improve the performance of spatial queries and that different structures are best suited for different applications. 相似文献
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P2P环境中的全局空间数据目录研究 总被引：10，自引：1，他引：9
P2P计算通过大量自治的节点协作共享资源与计算,为空间数据和空间操作的分布提供了新的分布式计算模式。分布在不同Peer上的空间数据库节点通过P2P协作构成一个超级全局空间数据库,全局空间数据目录是P2P环境下快速定位空间数据资源和空间计算节点的关键技术。Peer数据库节点的数据模式、元数据、资源状态参数等抽象为一系列关键词集合。全局目录基于Peer空间数据库节点的外包矩形进行动态聚类并建立P2P环境下的空间索引,支持Peer空间数据库节点的动态加入和退出,支持复杂空间查询和关键词查询。该文给出了全局空间数据目录的组织模型、P2P空间数据索引及空间资源发现算法。 相似文献
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Hot crime areas are always targeted for police patrol to deter crimes. While much research has studied the distribution patterns of hot crime areas, research on the spatial distribution of crime within hot crime areas remains limited. Using burglary records in a large Chinese city, the ‘hottest’ place with the highest crime density was located using two spatial temporal kernel density estimation methods. The results indicated that the majority of crime within hot crime areas was concentrated within a small area distant from the hot area's center. These results provide a micro view of crime distribution within hot crime areas. Our analysis indicates that the results will not be affected by the methods adopted in identification of hot areas. This research is expected to improve the efficiency of police patrols. 相似文献
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The concept of‘Beautiful China'is a new goal of ecological construction in the new era of socialism and aims to meet the needs of people as they strive for a better life.National land spatial planning is one major component of the Chinese state's overall planning for various spatial types.The concept of‘Beautiful China'is thus a leading goal of Chinese development in the second centenary.The background of this concept aims for‘ecological beauty'as well as the combined beauty of‘economy-politics-culture-society-ecology.'The construction of‘Beautiful China'therefore necessitates a differentiated evaluation index system that is built on the basis of local conditions.This concept is intimately related to land spatial planning and the idea of Beautiful China guides an important direction for this planning which itself provides an important mechanism and spatial guarantee for construction.The establishment of land spatial planning nevertheless needs to strengthen further discussion of the regional system of human-land relationship,point axis system,main functional division,sustainable development,resources and environmental carrying capacity as well as new urbanization,and the rural multi-system.The aim of this paper is to summarize current thinking in land spatial planning,scientifically analyze the natural geographical conditions,the socioeconomic development,the interrelationship of the land space,plan the goal,vision and path of land space,encourage the public to participate in and carry out dynamic evaluation,build an intelligent system platform for land and spatial planning to realize the goal of‘Beautiful China'from a geographical perspective.And they can also present key ideas relating to the compilation and implementation of land spatial planning. 相似文献
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Luc Anselin Sergio J. Rey Wenwen Li 《International journal of geographical information science》2014,28(11):2261-2280
Within a CyberGIS environment, the development of effective mechanisms to encode metadata for spatial analytical methods and to track the provenance of operations is a key requirement. Spatial weights are a fundamental element in a wide range of spatial analysis methods that deal with testing for and estimating models with spatial autocorrelation. They form the link between the data structure in a GIS and the spatial analysis methods. Over time, the number of formats for spatial weights implemented in software has proliferated, without any standard or easy interoperability. In this paper, we propose a flexible format that provides a way to ensure interoperability within a cyberinfrastructure environment. We illustrate the format with an application of a spatial weights web service, which is part of an evolving spatial analytical workbench. We describe an approach to embed provenance in spatial weights structures and illustrate the performance of the web service by means of a number of small experiments. 相似文献
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The damage of dwelling houses constitutes the primary cause of casualties and asset loss in seismic disasters that occurred in Chinese rural areas. The structure of houses is crucial for assessing the vulnerability of rural houses. However, at present, available data on rural housing structure are incomplete and their spatial scales are inconsistent. This paper estimated the amount and ratio of rural houses in five structures, namely ’wood’, ’brick’, ’mixed’, ’reinforced concrete’, and ’other’, for 2380 counties across China. With the percent-age sampling census data in 2005, four accuracy levels were specified. Then, a set of down-scaling models were established, where the impact of climate, economic development level and ethnic minority cultural factors on rural housing structure, as well as the spatial autocorrelation of neighboring spatial units were considered. Based on the estimation results, a database of county-level rural housing structure was established, based on which the vul-nerability of rural houses in different areas was clarified. 相似文献
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Chen Zhong Stefan Müller Arisona Xianfeng Huang Michael Batty Gerhard Schmitt 《International journal of geographical information science》2014,28(11):2178-2199
Urban spatial structure in large cities is becoming ever more complex as populations grow in size, engage in more travel, and have increasing amounts of disposable income that enable them to live more diverse lifestyles. These trends have prominent and visible effects on urban activity, and cities are becoming more polycentric in their structure as new clusters and hotspots emerge and coalesce in a wider sea of urban development. Here, we apply recent methods in network science and their generalization to spatial analysis to identify the spatial structure of city hubs, centers, and borders, which are essential elements in understanding urban interactions. We use a ‘big’ data set for Singapore from the automatic smart card fare collection system, which is available for sample periods in 2010, 2011, and 2012 to show how the changing roles and influences of local areas in the overall spatial structure of urban movement can be efficiently monitored from daily transportation.
In essence, we first construct a weighted directed graph from these travel records. Each node in the graph denotes an urban area, edges denote the possibility of travel between any two areas, and the weight of edges denotes the volume of travel, which is the number of trips made. We then make use of (a) the graph properties to obtain an overall view of travel demand, (b) graph centralities for detecting urban centers and hubs, and (c) graph community structures for uncovering socioeconomic clusters defined as neighborhoods and their borders. Finally, results of this network analysis are projected back onto geographical space to reveal the spatial structure of urban movements. The revealed community structure shows a clear subdivision into different areas that separate the population’s activity space into smaller neighborhoods. The generated borders are different from existing administrative ones. By comparing the results from 3 years of data, we find that Singapore, even from such a short time series, is developing rapidly towards a polycentric urban form, where new subcenters and communities are emerging largely in line with the city’s master plan.
To summarize, our approach yields important insights into urban phenomena generated by human movements. It represents a quantitative approach to urban analysis, which explicitly identifies ongoing urban transformations. 相似文献
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Domen Smole Marjan Čeh Tomaž Podobnikar 《International journal of geographical information science》2013,27(11):1809-1827
In this article we analyze a well-known and extensively researched problem: how to find all datasets, on the one hand, and on the other hand only those that are of value to the user when dealing with a specific spatially oriented task. In analogy with existing approaches to a similar problem from other fields of human endeavor, we call this software solution ‘a spatial data recommendation service.’ In its final version, this service should be capable of matching requests created in the user's mind with the content of the existing datasets, while taking into account the user's preferences obtained from the user's previous use of the service. As a result, the service should recommend a list of datasets best suited to the user's needs. In this regard, we consider metadata, particularly natural language definitions of spatial entities, a crucial piece of the solution. To be able to use this information in the process of matching the user's request with the dataset content, this information must be semantically preprocessed. To automate this task we have applied a machine learning approach. With inductive logic programming (ILP) our system learns rules that identify and extract values for the five most frequent relations/properties found in Slovene natural language definitions of spatial entities. The initially established quality criterion for identifying and extracting information was met in three out of five examples. Therefore we conclude that ILP offers a promising approach to developing an information extraction component of a spatial data recommendation service. 相似文献
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空间认同:城市空间研究转向中的知识前沿、趋势与启发 总被引：3，自引：2，他引：1
中国城市化进程的快速发展,促使人们不断解构、调整和重构对城市空间的认同,这是城市化发展中不容忽视的新问题。以Web of Science（WoS）为数据源,对国外城市空间认同研究进行了分析和知识再现。研究发现：① 城市空间认同是人们对城市发展中社会经济认同、文化认同、集体认同、身份认同与情感认同的集合。作为重要的国民意识,城市空间认同主题是国外学者关注的重要领域,对该领域研究的本质上是对城市空间实践中人文主义空间诉求的知识表征;② 在2008~2017年的国外城市空间认同研究中,美国、英国、澳大利亚等国家具有明显优势,国际合作研究网络主要在美洲-欧洲、欧洲-澳洲,以及澳洲-欧美之间;国外城市空间认同研究高被引文献注重对“空间多中心性”“地方与连续性”“城市社区”“城市公民身份”“空间绅士化”“地方主义”等方面的讨论。③ 未来研究更加倾向在“认同”“空间”“城市”“地理”“政治”“地方”,以及“社区”等新主题方面。相比较而言,国内对城市空间认同的研究较为欠缺,随着中国城市空间实践不断推向纵深阶段,需要强化城市空间认同研究的“理论自觉”。 相似文献
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基于空间数据库的多媒体图形查询信息系统研究——以苏州河环境综合整治为例 总被引：5，自引：2，他引：5
本文介绍作者自行开发的GIS软件系统———基于空间数据库的多媒体图形查询信息系统的内容、结构和功能 ,以及在环境规划管理方面的应用。阐明了系统可满足决策管理层和公共信息发布层等不同层次的应用需求 ,对环境工程项目的规划管理可作为示范和借鉴。说明本系统除具有一般GIS系统所具有的功能外 ,还把现代多媒体技术和GIS空间数据库技术结合起来 ,实现了在空间数据基础上的多媒体信息查询 ,丰富了GIS中属性数据查询的内容 ,提高了地图的可视性。详细介绍了一种地理信息系统的空间分析方法———包含分析的算法和在本系统中的具体应用———按多边形区域进行空间相关性关系查询。 相似文献
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国土空间开发建设适宜性评价研究进展 总被引：8，自引：2，他引：6
国土空间开发建设适宜性是优化国土空间开发格局、合理布局建设空间的依据,包括国土空间开发适宜性和建设用地适宜性两个方面。本文首先探讨二者的概念与内涵,然后从评价目标与视角、评价尺度与单元等多个角度梳理国土空间开发建设适宜性案例研究现状;进而总结归纳国土空间开发建设适宜性的指标体系及评价方法。分析发现：国土空间开发建设适宜性指标体系早期以工程地质条件为主,但目前涉及要素日益多元化,涵盖地质地貌、生态、经济、社会各方面;并已形成多要素叠置综合评价、空间作用及其趋势模拟、基于生态位的适宜性评价及参与式综合评价四种适宜性评价方法。今后应借鉴地理学、社会学、空间经济学、生态学等多学科理论,构建完善的国土空间开发建设适宜性研究体系,加强基础理论研究;推动指标体系规范与统一,完善评估框架与技术方法,研发开放式评价系统;构建可与空间管制政策对接的适宜性分类体系,扩展适宜性评价的案例研究和应用范围;同时应促进宏观空间开发适宜性和微观建设适宜性的统一和整合,响应“多规融合”的实践需求。 相似文献
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提出了一种新的动态空间索引结构X-Lists,设计实现了X-Lists的动态插入、动态删除、查找等算法,并进行了算法实验。X-Lists是一种支持高维点查询和区域查询的广义表,实验表明,X-Lists在索引构建与区域查找方面性能明显优于现有R-Tree及其改进索引结构。 相似文献
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Hua Shu Ci Song Ting Ma Yunyan Du Zide Fan 《International journal of geographical information science》2019,33(7):1355-1376
Variation in the spatial heterogeneity of points reflects the evolutionary process or mechanism of geographical events. The key to depicting this variation is quantifying spatial heterogeneity. In this paper, the spatial heterogeneity of a point pattern is defined as the degree of aggregation-type deviation from complete spatial randomness. In such a case, a goodness-of-fit-type statistic based on the distribution of nearest-neighbor distances called the level of heterogeneity (LH*) is regarded as a standard measurement, and a normalized version called the normalized level of heterogeneity (NLH*) is proposed for datasets with different point numbers and study region areas. Considering the complex integration calculation of LH* and NLH*, simulation experiments are implemented to test the capability of some classic nearest-neighbor statistics in quantifying spatial heterogeneity. The results showed that except for the standard LH* statistic, only Clark and Evans’ statistic (A-w) and Byth and Ripley’s statistic (H-xw) are robust. Statistics NLH*, (A-w) and (H-xw) are validated by quantifying the spatial heterogeneity of two-dimensional crime events, three-dimensional earthquake events and four-dimensional origin-destination (OD) events. The results indicate that these statistics all have a reasonable explanation in quantifying spatial heterogeneity for real-world geographical events of different types and with different dimensions. Compared with NLH*, Clark and Evans’ (A-w) statistic and Byth and Ripley’s (H-xw) statistic are recommended from the perspective of accessibility. 相似文献