Showing papers on "Choropleth map published in 2004"
TL;DR: In this article, the spatial prediction of point values from areal data of the same attribute is addressed within the general geostatistical framework of change of support; the term support refers to the domain informed by each datum or unknown value.
Abstract: The spatial prediction of point values from areal data of the same attribute is addressed within the general geostatistical framework of change of support; the term support refers to the domain informed by each datum or unknown value. It is demonstrated that the proposed geostatistical framework can explicitly and consistently account for the support differences between the available areal data and the sought-after point predictions. In particular, it is proved that appropriate modeling of all area-to-area and area-to-point covariances required by the geostatistical framework yields coherent (mass-preserving or pycnophylactic) predictions. In other words, the areal average (or areal total) of point predictions within any arbitrary area informed by an areal-average (or areal-total) datum is equal to that particular datum. In addition, the proposed geostatistical framework offers the unique advantage of providing a measure of the reliability (standard error) of each point prediction. It is also demonstrated that several existing approaches for area-to-point interpolation can be viewed within this geostatistical framework. More precisely, it is shown that (i) the choropleth map case corresponds to the geostatistical solution under the assumption of spatial independence at the point support level; (ii) several forms of kernel smoothing can be regarded as alternative (albeit sometimes incoherent) implementations of the geostatistical approach; and (iii) Tobler’s smooth pycnophylactic interpolation, on a quasi-infinite domain without non-negativity constraints, corresponds to the geostatistical solution when the semivariogram model adopted at the point support level is identified to the free-space Green’s functions (linear in 1-D or logarithmic in 2-D) of Poisson’s partial differential equation. In lieu of a formal case study, several 1-D examples are given to illustrate pertinent concepts.
318 citations
01 Mar 2004-Cartographica: The International Journal for Geographic Information and Geovisualization
TL;DR: This paper takes up the challenge of "reconstructing gis" by examining gis and governmental rationality by identifying similar shifts between the choropleth and the dasymetric map.
Abstract: This paper takes up the challenge of "reconstructing gis" by examining gis and governmental rationality. As an aspect of government, mapping is a vital source of geographic knowledge that informs political decision-making. Of particular importance to geographic governance and management are population distributions such as health, wealth, education, density, or criminality. Yet how these distributions have been mapped has shifted and been contested historically. Whereas in the early nineteenth century populations merely filled in pre-existing political areas, by the early twentieth century populations were understood as themselves defining areas and boundaries. Today, gis has returned to the earlier unproblematic politics of space. I explain these shifts by identifying similar shifts between the choropleth and the dasymetric map. Although commonly used, the choropleth is inadequate and misleading. I discuss the possible reasons for these shifts by re-emphasizing mapping as an aspect of geographic governance.
76 citations
Proceedings Article•
1 Jul 2004TL;DR: This work presents an Auditory Information Seeking Principle (AISP) (gist, navigate, filter, and details-on-demand) modeled after the visual information seeking mantra and proposes that data sonification designs should conform to this principle.
Abstract: We present an Auditory Information Seeking Principle (AISP) (gist, navigate, filter, and details-on-demand) modeled after the visual information seeking mantra [1]. We propose that data sonification designs should conform to this principle. We also present some design challenges imposed by human auditory perception characteristics. To improve blind access to georeferenced statistical data, we developed two preliminary sonifications adhering to the above AISP, an enhanced table and a spatial choropleth map. Our pilot study shows people can recognize geographic data distribution patterns on a real map with 51 geographic regions, in both designs. The study also shows evidence that AISP conforms to people’s information seeking strategies. Future work is discussed, including the improvement of the choropleth map design.
67 citations
TL;DR: In this paper, the authors show how dasymetric mapping can estimate the spatial distribution of aggregate level residential burglary within political boundaries in Massachusetts based on land use and housing data.
Abstract: With availability of crime data to the public via sources such as the Uniform Crime Reports, and increasing geographic information system (GIS) capabilities for mapping crime, macro-level studies of crime have advanced knowledge of how crime is distributed over large areas. Choropleth mapping, commonly used in macro-level studies, visually displays data by assigning the number of crimes or crime rate to the corresponding spatial unit and using different shades or textures for each value or classified values creating a thematic map. However, crime incidents or crime rates are not dispersed evenly within spatial units, and choropleth mapping masks the underlying nuances of the distribution. Artificial boundaries, along with variations in the size of the unit of analysis, can further distort the true distribution of crime. Dasymetric mapping provides a methodology for refining the distribution of crime within a spatial unit. It does so by using additional data, such as land use and census data, to provide a realistic estimate of how crime may be distributed within the units of analysis. Dasymetric mapping is also useful in creating density maps to reveal clusters of crime normally masked with choropleth maps. This paper will show how dasymetric mapping can estimate the spatial distribution of aggregate level residential burglary within political boundaries in Massachusetts based on land use and housing data.
63 citations
TL;DR: In this paper, the use of the frequency histogram legend (FHL) as a substitute to traditional legends in both classed and unclassed choropleth maps is presented.
Abstract: This article presents the use of the frequency histogram legend (FHL) as a substitute to traditional legends in both classed and unclassed choropleth maps. Great variation in the size of mapping un...
22 citations
TL;DR: The tmap package is presented, a set of Stata programs designed to draw five kinds of thematic maps: choropleth, proportional symbol, deviation, dot, and label maps, intended to depict area data.
Abstract: Thematic maps illustrate the spatial distribution of one or more variables of interest within a given geographic unit. In a sense, a thematic map is the spatial analyst's equivalent to the scatterp...
19 citations
29 Jul 2004
10 citations
1 Nov 2004
TL;DR: A research programme which has designed a visualisation of attribute and choropleth spatial uncertainty using the Hexagonal or Rhombus (HoR) hierarchical spatial data structure is extended, which is termed – the trustree.
Abstract: Attribute and spatial uncertainty are defined and put into context for this research. This paper then extends on a research programme which has designed a visualisation of attribute and choropleth spatial uncertainty using the Hexagonal or Rhombus (HoR) hierarchical spatial data structure. Using the spatial data model in this fashion is termed – the trustree. To understand this progression, a brief explanation of this research programmes past history must be covered. The New Zealand 2001 census is used as an exemplarity dataset to express attribute uncertainty and choropleth boundary uncertainty (termed spatial uncertainty). An internet survey was conducted to test the usability of the trustree, which was used as a transparent tessellation overlay and a value-by-area (VBA) display within a population choropleth map. Two other visualisation of attribute uncertainty methods – blinking areas and adjacent value were also incorporated into the survey. Participants were required to rank, from 1 to 6, six grid cells which overlaid the uncertainty visualisations, in order from the most accurate to the most uncertain cell, respectively. These ranking results were correlated with the actual ranks, providing a metric of usability for each visualisation method. The blinking areas method was the most effective, followed by adjacent value, VBA trustree and the transparent HoR trustree. The time taken for a participant to rank each visualisation’s cells was collected – there is an 82% correlation between the time taken and the final usability results obtained.
2 citations
Journal Article•
TL;DR: In this article, the authors place the emphasis on data visualization with a topologically correct geography, the real purpose of mapping, rather than on the geography per se with a visually bias and often unhelpful data representation.
Abstract: With the advent of computer cartography and GIS there has been an increasing emphasis on map visualization, not only in terms of the use of color but also in terms of methods of data representation. Enough computer power is now available on the average PC to construct all but the most complex maps. Mapping is a way of visualizing the world and no map is without some sort of distortion. When mapping social phenomena however, there is ample reason to place the emphasis on data visualization with a topologically correct geography - the real purpose of mapping, rather than on the geography per se with a visually bias and often unhelpful data representation.
1 citations
1 Jan 2004
TL;DR: This chapter describes the various methods used by the registry, the definition of cancer entities, the basis for social class classification, the use of statistical procedures, the choice of high-risk criteria, the method of producing Poisson generated expected numbers, the choices of a mapping strategy, and the absence of formal cluster analysis.
Abstract: This chapter describes the various methods used by the registry, the definition of cancer entities, the basis for social class classification, the use of statistical procedures, the choice of high-risk criteria, the method of producing Poisson generated expected numbers, the choice of a mapping strategy, and the absence of formal cluster analysis used in this book. Estimates of the number of cases to be expected over the period in each census tract were obtained by applying all-race rates for the entire county to the population of each census tract by age, calculating the expected number of cases, and combining them to produce an indirectly age-adjusted total. That is directly compared to the observed number in the form of a standardized incidence ratio (SIR), roughly equivalent to a relative risk. Maps of health events can be divided into spot maps and area maps. Health event maps have more commonly employed area, or choropleth, maps, which are capable of showing differences between rates using different colors or shadings for the different areas, that is, different defined populations, according to the various levels of risk. Most of these maps are produced for the purpose of displaying patterns thought to correspond to specific patterns of exposure, or for the purpose of identifying autocorrelations between the rates of adjacent areas.
24 May 2004
TL;DR: Broad access to interactive mapping of region values, user-controlled dynamic sliders that encourage involvement, and annotation and alternative views that facilitate comparison and provide a gentle path toward sophisticated hypothesis generation about map patterns are provided.
Abstract: Dynamic condition choropleth maps (CCmaps) serves many purposes. CCmaps provides• broad access to interactive mapping of region values,• user-controlled dynamic sliders that encourage involvement, and• annotation and alternative views that facilitate comparison and provide a gentle path toward sophisticated hypothesis generation about map patterns.