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1.
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   

2.
《The Journal of geography》2012,111(5):206-213
Abstract

The concept of scale is fundamental to geography, yet the definitions for “scale” and related spatial terms can be confusing to those working in other spatial science disciplines. This is particularly true in the emerging multidisciplinary world of integrated remote sensing and geographic information systems, or IGIS's, where data of different types and at various spatial and temporal scales are combined to support complex space-time data analyses. Without a basic lexicon of accepted scale terms, working within an IGIS can breed confusion in the interpretation of data and the models that result from an IGIS construct. This paper provides some terminologies of scale that can be used as a framework for a multidisciplinary lexicon of accepted scaling terms and describes their relationships to an IGIS. It also illustrates how scaling terms can be potentially misunder stood when applied to geographic techniques that are used in disciplines related to geography.  相似文献   

3.
ABSTRACT

Spatial point tracks are of concern for an increasing number of analysts studying spatial behaviour patterns and environmental effects. Take an epidemiologist studying the behaviour of cyclists and how their health is affected by the city’s air quality. The accuracy of such analyses critically depends on the positional accuracy of the tracked points. This poses a serious privacy risk. Tracks easily reveal a person’s identity since the places visited function as fingerprints. Current obfuscation-based privacy protection methods, however, mostly rely on point quality reduction, such as spatial cloaking, grid masking or random noise, and thus render an obfuscated track less useful for exposure assessment. We introduce simulated crowding as a point quality preserving obfuscation principle that is based on adding fake points. We suggest two crowding strategies based on extending and masking a track to defend against inference attacks. We test them across various attack strategies and compare them to state-of-the-art obfuscation techniques both in terms of information loss and attack resilience. Results indicate that simulated crowding provides high resilience against home attacks under constantly low information loss.  相似文献   

4.
Abstract.

A formal, yet practical, GeoRelational Data Model (GRDM) is presented for the logical database design phase of the development of spatial information systems. Geographic applications are viewed in the context of information systems development. The generic needs of modelling spatial data are analyzed; it is concluded that they are not served satisfactorily by existing data models, so specifications of modelling tools for spatial application design are given. GRDM provides a set of representational constructs (relations and layers for the logical schema; virtual layers, object classes and spatial constraints for the user views) on top of well-established models. It constitutes part of a full, easily automated application design methodology. Extensive examples demonstrate the relevance, and ease-of-use of the platform-independent GRDM.  相似文献   

5.
《The Journal of geography》2012,111(6):243-250
Abstract

Teaching students to gain a spatial perspective is one of the most difficult yet important components of geographic education. This paper presents a series of activities designed to develop a more comprehensive understanding of spatial concepts among students in introductory geography courses. The activities and content are most appropriate for high school or university undergraduate students. An evaluation of these activities demonstrates that they enhance the student's spatial perspective and their understanding of the role of spatial concepts in geography.  相似文献   

6.
《The Journal of geography》2012,111(3):141-142
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7.
Abstract

A raster/quadtree geographical information system (GIS) was established For a 932 ha natural area in central Missouri. The GIS contained map layers depicting vegetative cover from 1939 to 1982, soils, topographic aspect and distance from a forest seed source. Discriminant function analysis was used to quantify and describe ecological succession on the area during this period. The calibration of discriminant functions is discussed, as are the statistical and spatial validations of the model. It was concluded that this approach provides a useful technique to examine long-term temporal phenomena in a spatial context.  相似文献   

8.

Rather than seeing the oceans as an expansive void, researchers using acoustic technologies can detect the heterogeneity of biological resources and view the marine environment as a three-dimensional landscape. Underwater remote sensing, using acoustics, provides high resolution maps of the spatial distribution of organisms in aquatic ecosystems. Analyzing the spatial pattern of species distribution within the water column and the impact of that organization on ecological processes bridges the fields of fisheries and spatial analysis. Tools and concepts familiar to geographers, such as remote sensing, GIS, and landscape ecology, contribute to the investigation of large lake and marine ecosystems.  相似文献   

9.
Abstract

Large spatial interpolation problems present significant computational challenges even for the fastest workstations. In this paper we demonstrate how parallel processing can be used to reduce computation times to levels that are suitable for interactive interpolation analyses of large spatial databases. Though the approach developed in this paper can be used with a wide variety of interpolation algorithms, we specifically contrast the results obtained from a global ‘brute force’ inverse–distance weighted interpolation algorithm with those obtained using a much more efficient local approach. The parallel versions of both implementations are superior to their sequential counterparts. However, the local version of the parallel algorithm provides the best overall performance.  相似文献   

10.
PurposeTo examine the impact of public bus system on spatial burglary pattern in a Chinese urban context, as well as the spatial variation of this impact.MethodsLocal Moran's I, boxplot-based classification, geo-visualization, Chi-square test, and correlation analysis are used to explore the spatial coupling relationships between bus stops and burglary. Guided by routine activity approach, negative binomial regressions are performed for the developed and developing parts of the DP peninsula, as well as the whole peninsula based on proxies of potential offenders, guardians, targets, and spatial dependence.ResultsStatistically positive correlations are observed between burglary count and bus stop service capability. However, net of other factors, one more unidirectional bus route is expected to reduce burglary by nearly 2 percent for the whole area, and 4 percent for the developed area, while no statistically significant relationship is found for the developing area.ConclusionsThe bus-burglary relationships differ between the developed and developing urban areas. For the former, although burglaries concentrate around bus stops with higher service capability, the increase of bus service capability has a net impact of slightly depressing the occurrence of burglaries. Four possible mechanisms explaining this negative bus-burglary relationship in the DP peninsula are presented.  相似文献   

11.
Abstract

During the 1980s techniques for analysis of geographical patterns have been refined to the point that they may be applied to data from many fields. Quantitative spatial analysis and existing functions available in geographical information systems (GIS) enable computerized implementations of these spatial analysis methods. This paper describes the application of quantitative spatial analysis and GIS functions to analysis of language data, using the extensive files of the Linguistic Atlas of the Middle and South Atlantic States (LAMSAS). A brief review of recent development of using quantitative and statistical methods for analysing linguistic data is also included.  相似文献   

12.
《The Journal of geography》2012,111(5):208-219
ABSTRACT

Geography textbooks contain chapter or review questions that may engage students in spatial thinking. This research used Jo and Bednarz’s (2009) Taxonomy of Spatial Thinking to evaluate the percentage of spatial thinking questions in four university-level world geography course textbooks. The results from this study were then compared to the findings in Jo and Bednarz’s (2009) analysis of high school geography textbooks. Thirty-five percent of university level textbook questions are related to spatial thinking compared to twenty-four percent in high school geography textbooks. The results provide information useful to stakeholders, such as teachers, administrators, and textbook writers and may help these stakeholders to consciously incorporate the three components of spatial thinking as defined by the National Research Council (2006). A simplified taxonomy for identifying spatial-thinking concepts in textbook review questions is also suggested.  相似文献   

13.
Abstract

A neglected aspect of facility location problems is the geometric representation of the facilities sited and clients served. Point objects represent these entities in most facility location problems. This can cause solution error and limit the range of potential solutions. The increasing capabilities of geographical information systems (GIS) to represent, store and manipulate spatial entities provides a substantial but unrealized potential for more sophisticated geometric representation in facility location problems. This paper provides a framework for realizing this potential. Specifically, this paper: (i) synthesizes existing formulations; (ii) develops a unified mathematical framework; (iii) identifies feasible computational strategies that can be implemented within a GIS framework, and; (iv) discusses potential GIS-based solution algorithms.  相似文献   

14.
Abstract

Progress in technical database management systems offers alternative strategies for the design and implementation of databases for geographical information systems. Desirable extensions in the user data types and database management are reviewed. A prototype geographical database tool-kit, SIRO-DBMS, which provides some spatial data types and spatial access methods as external attachments to a kernel relational database management system, is described. An ability to fragment a large set of entities into several relations while retaining the ability to search the full set as a logical unit is provided. Implementation of the geometric data types is based on mapping the types of data into a set of attributes of the atomic types supported by the kernel and specifying the relational designs for the set of atomic attributes.  相似文献   

15.

Spatial barriers to employment limit women's job opportunities, but their effects differ among racial/ethnic minority groups. This study evaluates the degree of spatial mismatch for minority women and men by comparing the commuting times of African American, Latino, and white workers in the New York metropolitan region. Using Public Use Microdata for 1980 and 1990, we perform a partial decomposition analysis to assess the role of spatial mismatch in lengthening commuting times for minority workers. The results show that African American men and women living in the center of the region have poorer spatial access to employment than their white counterparts. In the suburbs, African American women and Latinas suffer no spatial mismatch; rather, their longer commuting times reflect greater reliance on mass transit. Comparison with 1980 findings reveals little change in spatial mismatch over time despite significant economic and social restructuring in the 1980s. Spatial barriers still limit employment prospects for the majority of minority women living at the core of the region.  相似文献   

16.
David Lulka 《Urban geography》2013,34(8):1119-1143
Abstract

Nonhuman animals are part of the dynamism that typifies cities, yet prior research has obscured this condition by focusing upon a limited subset of animals and the privatized spaces that contain them. Consequently, previous research provides little guidance in developing a post-human conception of cities. This paper redresses this deficiency by redefining conceptions of “the public” and analyzing data from San Diego's Dead Animal Removal Program (DARP). Commensurate with modern political conceptions, “the public” is defined simultaneously as a spatial formation and (akin to democracies) a quantitative body of bodies. The DARP data indicate the pervasive presence of nonhuman animals in urban environments and the difficulties they face. As a nexus, the DARP illustrates how urban practices and bureaucratic systems reinstantiate “the public” in humanized form through the death and disposal of nonhumans. These hybrid relations challenge geographic methods.  相似文献   

17.
ABSTRACT

Big data have shifted spatial optimization from a purely computational-intensive problem to a data-intensive challenge. This is especially the case for spatiotemporal (ST) land use/land cover change (LUCC) research. In addition to greater variety, for example, from sensing platforms, big data offer datasets at higher spatial and temporal resolutions; these new offerings require new methods to optimize data handling and analysis. We propose a LUCC-based geospatial cyberinfrastructure (GCI) that optimizes big data handling and analysis, in this case with raster data. The GCI provides three levels of optimization. First, we employ spatial optimization with graph-based image segmentation. Second, we propose ST Atom Model to temporally optimize the image segments for LUCC. At last, the first two domain ST optimizations are supported by the computational optimization for big data analysis. The evaluation is conducted using DMTI (DMTI Spatial Inc.) Satellite StreetView imagery datasets acquired for the Greater Montreal area, Canada in 2006, 2009, and 2012 (534 GB, 60 cm spatial resolution, RGB image). Our LUCC-based GCI builds an optimization bridge among LUCC, ST modelling, and big data.  相似文献   

18.
This article provides new empirical evidence on the patterns of firm entry across sectors and space. Based on Pavitt’s four manufacturing industry categories—supplier-dominated, scale-intensive, specialized suppliers, and knowledge-based—we use China’s firm-level database, covering all manufacturing firms with sales above 5 million RMB from 1998 to 2008, to investigate the relation between spatial patterns of new entry firms and industrial structure change and firm heterogeneity. Based on our analysis, there are three key findings. First, industrial structure change plays an important role in influencing the sectoral pattern of new firm entry. Second, the transformation from a supplier-dominated industry to a scale-intensive industry from 1998 to 2008 in China has largely influenced spatial patterns of new entry firms (mainly spatial agglomeration and entry similarity between regions). Third, the heterogeneity of firms (mainly firm ownership, firm size, and technological relatedness) affected the location choice of new entry firms. Based on our findings, we conclude that the importance of industrial structure change and the heterogeneity of firms in revealing the spatial pattern of new entry firms should receive more attention. Key Words: China, firm entry, firm heterogeneity, industrial structure change, sectoral and spatial pattern.  相似文献   

19.
ABSTRACT

This paper describes an empirical case study of the Subiaco town centre in Western Australia. The research method employs geospatial mapping of archival and contemporary data sources to explore the town centre's changing spatial structure and high street morphology at the micro-scale over the past century. Once a thriving retail and business centre, Subiaco's (and possibly the state's), premier retail high street destination is now being compromised as the disruptive influence of online retailing gains further traction in the marketplace. Retail disruption provides the paper's conceptual foundation. Agents of disruption include the processes of creative destruction and innovation diffusion, which together with macro-economic factors help to explain the centre's evolution over time and space. The paper examines changes in the town centre's morphological character including residential gentrification, a growing dominance of fast food outlets, an overabundance of comparison stores and a more gendered offering in retail and personal services establishments. The paper also refers to the potential of the town centre to regain its past residential status as a means of fostering economic growth and renewal and suggests that this will only be achieved with radical intervention at the policy and planning level.  相似文献   

20.
Abstract

This paper reports on software to construct alternative weight matrices and to compute spatial autocorrelation statistics, namely the Moran coefficient and the Geary coefficient using Arc/Info’s data structure. As such it is an addition to recent efforts in linking GIS with exploratory spatial data analysis. The software is interfaced with Arc/Info via the Arc Macro Language (AML) so that it can be run in the ARC environment. This allows the user to perform exploratory analysis within GIS which may provide insights in subsequent spatial analysis and modelling.  相似文献   

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