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  2013年   24篇
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1.
One of the most fundamental steps in map creation is the transformation of information from the surface of a globe onto a flat map. Mapmakers have developed and used hundreds of different map projections over the past 2,000 years, yet there is no perfect choice because every map projection uniquely alters some aspect of space during the transformation process. Detailed information about the type, amount, and distribution of distortion is essential for choosing the best projection for a particular map or data set. The distortion inherent in projections can be measured and symbolized much like any other map variable. Methods for symbolizing map projection distortion are reviewed, with each method described and illustrated in graphical form. The symbolization methods are collected under ten separate headings organized from simple to more complex in terms of interpretation. Most of these methods are highly effective at communicating distortion, yet they are rarely used beyond textbooks and technical documentation. Map projections and the distortions they carry need to be better understood by spatial data developers, distributors, and users. Map distortion should be carried along with map data as confidence layers, and the easily accessible distortion displays should be available to help in the selection of map projections. There is a suitably wide array of symbolization methods to match any need from basic education to research.  相似文献   
2.
The discovery, interpretation, and presentation of multivariate spatial patterns are important for scientific understanding of complex geographic problems. This research integrates computational, visual, and cartographic methods together to detect and visualize multivariate spatial patterns. The integrated approach is able to: (1) perform multivariate analysis, dimensional reduction, and data reduction (summarizing a large number of input data items in a moderate number of clusters) with the Self-Organizing Map (SOM); (2) encode the SOM result with a systematically designed color scheme; (3) visualize the multivariate patterns with a modified Parallel Coordinate Plot (PCP) display and a geographic map (GeoMap); and (4) support human interactions to explore and examine patterns. The research shows that such "mixed initiative" methods (computational and visual) can mitigate each other's weakness and collaboratively discover complex patterns in large geographic datasets, in an effective and efficient way.  相似文献   
3.
Over the last three decades analytical cartography has grown from Tobler's concept of "solving cartographic problems" into a broader and deeper scientific specialization that includes the development and expansion of analytical/mathematical spatial theory and model building. In many instances Tobler himself has led the way to these new insights and developments. Fundamental concepts begin with Tobler's cartographic transformations; Nyerges' deep and surface structure and data levels; and Moellering's real and virtual maps; the sampling theorem; and concepts of spatial primitives and objects. This list can be expanded to include additional analytical concepts such as spatial frequencies, spatial surface neighborhood operators, information theory, fractals, Fourier theory, topological network theory, and analytical visualization, to name a few. This base of analytical theory can be employed to analyze and/or develop such things as spatial surfaces, terrain analysis, spatial data schemas, spatial data structures, spatial query languages, spatial overlay and partitioning, shape analysis, surface generalization, cartographic generalization, and analytical visualization. More analytical uses of theory, strategies of analysis, and implementations are being developed and continue to multiply as the field continues to grow and mature. A primary goal is to expand the mathematical/analytical theory of spatial data analysis, and theory building and analytical visualization as analytical cartography takes its place in the geographic information sciences. The research future for this area appears very bright indeed.  相似文献   
4.
The most straightforward approaches to temporal mapping cannot effectively illustrate all potentially significant aspects of spatio-temporal patterns across many regions and times. This paper introduces an alternative approach, bicomponent trend mapping, which employs a combination of principal component analysis and bivariate choropleth mapping to illustrate two distinct dimensions of long-term trend variations. The approach also employs a bicomponent trend matrix, a graphic that illustrates an array of typical trend types corresponding to different combinations of scores on two principal components. This matrix is useful not only as a legend for bicomponent trend maps but also as a general means of visualizing principal components. To demonstrate and assess the new approach, the paper focuses on the task of illustrating population trends from 1950 to 2000 in census tracts throughout major U.S. urban cores. In a single static display, bicomponent trend mapping is not able to depict as wide a variety of trend properties as some other multivariate mapping approaches, but it can make relationships among trend classes easier to interpret, and it offers some unique flexibility in classification that could be particularly useful in an interactive data exploration environment.  相似文献   
5.
The GeoJabber concept, protocol, and working prototype software introduced here enable same-time, different-place collaborative geovisualization. The key problem this work addresses is how to turn geovisual software states into persistent textual representations that can be shared between users. In the current implementation, GeoJabber leverages three key Open Source technologies: the GeoViz Toolkit, the Jabber protocol, and XStream. GeoJabber is the first project to support same-time different-place geovisualization tool state sharing. As part of this effort, this paper presents a typology of sharable geovisualization software states, rooted in the concepts of data, display, and category.  相似文献   
6.
Virtual environments and related technology generate interest and excitement. Their power is strengthened with empirical evidence of their utility for scientific inquiry and decision-making. This paper reports on a study to evaluate the effectiveness of virtual environment (VE) presentations about issues typical of those facing decision makers in a rapidly growing urban area. The presentations consisted of the explanation and visualization of two phenomena—groundwater overdraft and the urban heat island. The virtual environment utilized in this study, Arizona State University's Decision Theater, is purported to help policy makers and the larger community visualize complex model output and make decisions about scientific issues. To begin to assess these claims, we carried out a user test during which a group of research participants were given two surveys, one before the presentations, to determine a priori understanding, and a second afterwards, with the same questions. This methodology allowed us to carry out within-subjects tests concerning contrasting phenomena, in order to assess two primary hypotheses: (1) knowledge and perceptions of environmental phenomena will change after the viewing, and (2) understanding will vary based on the phenomena in the presentations. Our analysis shows at least some level of support for the hypotheses, with evidence that the virtual environment positively influenced understanding, and that there may be important differences in insight generation based on characteristics of the phenomena represented. Finally, we outline critical areas of future research to further knowledge about the impact of visual VE settings on understanding and decision making.  相似文献   
7.
The paper reports on an experimental study aimed at assessing the usability of five different interactive tools for exploratory analysis of geographically referenced data implemented in CommonGIS. Usability was assessed in terms of tool learnability, memorability, and user satisfaction. The study provided valuable data concerning the usability of each individual tool; we also derived some conclusions relevant to geovisualization techniques in general. We found that users were, in principle, able to understand and adopt the new ideas of map interactivity and manipulability. However, these ideas needed to be appropriately introduced; people could hardly grasp them just from the appearance of the maps and controls. An introductory demonstration was sufficient to understand the purposes of the interactive tools, and a short training session enabled people to use them. The importance of educating users is a particular challenge for geovisualization tools that are intended to be accessed over the Internet.  相似文献   
8.
An area cartogram is a transformed map on which areas of regions are proportional to statistical data values; it is considered to be a powerful tool for the visual representation of statistical data. A circle cartogram is a type of area cartograms, on which regions are represented by circles. Its first construction algorithm is proposed by Dorling in 1996, based on the following requirements to construct visually elegant cartograms: 1) maintain the similarity of configurations between circles and regions, 2) express the contiguity of regions on cartograms if possible, and 3) avoid overlap of circles. The algorithm is widely used for its easiness to use and its ability to express a spatial distribution of data; however, the relative positions of circles on cartograms sometimes greatly differ from the geographical maps, since the algorithm does not consider the first requirements explicitly. In this paper, it is first pointed out that the construction problem of circle cartograms resembles that of distance cartograms, and the only difference is the existence of third requirement. Then a new construction method for circle cartograms is proposed based on the distance cartogram construction method; the proposed method is formulated as non-linear minimization with inequality constraint conditions. Finally its applicability is confirmed using dataset, including the comparison with the result of previous algorithm.  相似文献   
9.
The quality of dynamic map symbols plays an important role in the representation of spatial-temporal changes. This paper reports an investigation into the quality of dynamic symbols. To assess the quality of such symbols, a set of traffic flow data is used for the production of different kinds of dynamic maps, with focus on four variables, i.e. size, color, frame rate and display format. Two quantitative measures are used for analysis, i.e. deviation and response time. A set of traffic data is used for the production of dynamic maps for evaluation. The experimental results show that the size is more efficient and more effective than color for dynamic maps with the same frame rate and display format. The most efficient and effective color class number is 10 on the large format display such as 1024 × 768 pixels. And the most efficient and effective size class number is 15 on large format display such as 1024 × 768 pixels. The effective frame rate for dynamic map animation is smaller than that of the general animation on the Internet or Quick Time and AVI format video. The most efficient and most effective frame rate is 3 frames per second in the color expression and 6 frames per second in the size expression. In sum, the effective and efficient value of color, size and frame rate on large format display is less than the value on the small format display. These results suggest the frame rate should be reduced on the small format display. It is hoped that the results from this study will be of help in the design of effective and efficient dynamic map symbols for geographical information visualization.  相似文献   
10.
A hybrid system that integrates two-dimensional (2D) GIS and three-dimensional (3D) visualization has been developed to provide unique solutions to application domains where traditional 2D GIS and 3D visualization cannot alone provide a solution. In this paper, we focus on three key issues in realizing such an integrated system, including large-scale terrain rendering, 2D and 3D combination display (for example, rendering 2D GIS layers in 3D space), expanding traditional 2D GIS analysis functions into a 3D environment, and visualizing 3D geographical data. A generic framework is developed to integrate 3D visualization with various types of 2D GIS, such as commercial GIS software, open source GIS software and spatial databases. A prototype 2D and 3D hybrid system that seamlessly integrates 2D GIS (developed with ArcEngine) and 3D rendering engine (developed with DirectX) is then developed based on the framework. In this hybrid system, 2D and 3D data are viewed within the same scene. Multiple 2D GIS layers are overlaid on the base terrain using a Level of Detail (LOD) model. Advanced query functions, data accessing, data management and spatial analysis, which are executed in the traditional 2D GIS, are provided to users in a 3D environment by continuously transforming information between the 2D GIS subsystem and the 3D subsystem. The 3D data are organized and displayed by Keyhole Markup Language (KML) and textured 3D models in the COLLAborative Design Activity (COLLADA) format. The prototype demonstrates that this hybrid system has effectively addressed the three key issues identified above and that it can seamlessly integrate 2D GIS and 3D visualization. The hybrid system has great potential to be employed in many application domains, such as urban planning, landscape design and environmental decision making, among others, to enhance the 3D design capability and facilitate public participation in the planning, design and decision-making process.  相似文献   
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