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Geospatial Visualization

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#Choropleth
#Proportional Symbols

Choropleth

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Description

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Map

Color-codes named regions on a geographical map in proportion to associated numeric data.

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Features

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  • Choose to linearly, logarithmically, or exponentially scale each individual dimension of numeric data.
  • Map legends for each dimension of annotation show how the extrema of the data are represented as colors or circle sizes.

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Examples

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Implementation Details

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Expects a table with:

  • A text attribute that describes that datum's region name (for example, "India" or "Indiana").
  • A numeric attribute that will determine that region's color.

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Usage Hints

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  • Not suitable if your data that contain small countries. For example, Singapore is too small a geographic region to be visible on the map when the region is colored. We recommend the user select the circle Geomap if data on smaller geographic regions is important to analysis.
  • Requires that each country be identified using its name from the list Country names recognized by Geo Maps.
  • Requires that each U.S. state be identified using its name from the list U.S. state names recognized by Geo Maps.

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Description

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Produce maps of nations in the world or of the United States which are annotated according to any numeric data with colored regions or with circles of various sizes and colors.

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Features

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  • Draw circles at any coordinates with size and color reflecting up to three associated dimensions of numeric data.
  • Choose to linearly, logarithmically, or exponentially scale each individual dimension of numeric data.
  • Map legends for each dimension of annotation show how the extrema of the data are represented as colors or circle sizes.

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Examples

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Image Removed
Download PDF

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Implementation Details

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Expects a table with numeric attributes that:

  • Describe that datum's longitude in degrees (from -180 to +180).
  • Describe that datum's latitude in degrees (from -90 to +90).
  • Determine the size of the circle at that coordinate.
  • Determine the color of the circle at that coordinate.

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Usage Hints

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  • If you have region names but not latitude and longitude data in your table, you can still easily produce a circle-annotated map using the Geocoder algorithm, which will find the coordinate data for each region name and add it to the table.
  • There is no perfect map projection -- the choice depends on your application. We recommend:
    • Albers equal-area conic if preserving area is important.
    • Lambert conformal conic if preserving angles (or shapes) is important.
    • Mercator if presenting a familiar and fairly standardized projection is important.
  • The color-region Geomap is not suitable if your data that contain small countries. For example, Singapore is too small a geographic region to be visible on the map when the region is colored. We recommend the user select the circle Geomap if data on smaller geographic regions is important to analysis.
  • The color-region Geomap requires that each country be identified using its name from the list Country names recognized by Geo Maps.
  • The color-region Geomap requires that each U.S. state be identified using its name from the list U.S. state names recognized by Geo Maps.

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See Also

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Proportional Symbol Map

Maps geospatial coordinates as circles that can be size- and color-coded in proportion to associated numeric data.

Geospatial Network Layout with Base Map

Overlaying a network on a geographical map

Examples

See these sections of the Sci2 tutorial:

Incoming Links
spacesSCI2TUTORIAL