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cartogram

 
Dictionary: car·to·gram   (kär'tə-grăm') pronunciation
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n.
A presentation of statistical data in geographical distribution on a map.

[French cartogramme : carte, map (from Old French, card , from Latin charta, carta, paper made from papyrus; see card1) + -gramme, a record (from Late Latin gramma, something written; see -gram).]


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Statistics Dictionary: cartogram
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A distorted map in which regions are drawn not to an areal scale but to some other scale such as population. Some cartograms attempt to retain the shape of the geographical region they represent; others, such as the rectangular cartogram illustrated opposite, use a single shape to represent all regions of equal importance.




Rectangular cartogram. The diagram shows variation in turnout (the proportion of the electorate who actually cast their votes) in the British constituencies in the 1992 general election. Each constituency is represented by a rectangle whose area indicates the physical size of the constituency. The big conurbations (Greater London, Birmingham, Manchester, etc.) are indicated as outlined regions. Somewhat paradoxically, turnout is lower in city centres than in the rural constituencies.



Casement plot. The relation between the time intervals before and after eruptions of *Old Faithful, shown separately for different lengths of the intervening eruption.


Geography Dictionary: cartogram
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Broadly defined as a map using statistical symbols, a more specialist usage defines a cartogram as a type of map transformation based on a scale other than a true scale. For example, a voting map of Britain may show the size of counties in relation to the numbers of voters in each electoral unit, or an economic cartogram of the world may show countries drawn in proportion to their per capita GNP. Certain ‘rules’ are followed, as far as possible: the shapes of the countries and regions involved are preserved, although often stylized, and they are positioned in the correct geographical locations with respect to each other. Obviously, distortions occur, but the trick is to preserve the original shapes and positions enough to make the units recognizable; computers have helped in this, but the best examples are still produced by hand.

Veterinary Dictionary: cartogram
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A map showing the distribution of a population by area.

Wikipedia: Cartogram
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Area cartogram of the United States, with each county rescaled in proportion to its population. Colors refer to the results of the 2004 U.S. presidential election popular vote.
Cartogram showing Open Europe estimate of total European Union net budget expenditure in euros for the whole period 2007-2013 per capita, based on Eurostat 2007 population estimates (Luxembourg not shown).

Net contributors      -5000 to -1000 euro per capita      -1000 to -500 euro per capita      -500 to 0 euro per capita
Net recipients
     0 to 500 euro per capita      500 to 1000 euro per capita      1000 to 5000 euro per capita      5000 to 10000 euro per capita      10000 euro plus per capita      n/a

A cartogram is a map in which some thematic mapping variable – such as travel time or Gross National Product – is substituted for land area. The geometry or space of the map is distorted in order to convey the information of this alternate variable. There are two main types of cartograms: area and distance cartograms.

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Area cartograms

An area cartogram is sometimes referred to as a value-by-area map or an isodemographic map, the latter particularly for a population cartogram, which illustrates the relative sizes of the populations of the countries of the world by scaling the area of each country in proportion to its population; the shape and relative location of each country is retained to as large an extent as possible, but inevitably a large amount of distortion results. Other synonyms in use are anamorphic map and density-equalizing map.[1][2] The German word for cartogram is Kartenanamorphote, not Kartogramm.[3]

Distance cartogram

A distance cartogram may also be called a central-point cartogram. This form is typically used to show relative travel times and directions from vertices in a network.

One of the first cartographers to generate cartograms with the aid of computer visualization was Waldo Tobler of UC Santa Barbara in the 1960s. Prior to Tobler's work, cartograms were created by hand (as they occasionally still are). A number of software packages generate cartograms. Two examples of computer-generated cartograms are shown on the right.

See also

Further reading

  • Campbell, John. Map Use and Analysis. New York: McGraw-Hill, 2001.
  • Gillard, Quentin. "Places in the News: The Use of Cartograms in Introductory Geography Courses." Journal of Geography. 78 (1979): 114-115.
  • Tobler, Waldo. "Thirty-Five Years of Computer Cartograms." Annals of the Association of American Geographers. 94 (2004): 58-73.
  • Vescovo, Victor. "The Atlas of World Statistics." Dallas: Caladan Press, 2005.

External links

Search Wikimedia Commons Wikimedia Commons has media related to: Cartograms

References

  1. ^ Gallery of Data Visualization - Bright Ideas
  2. ^ UNEP GRID Ardenal: Anamorphic Maps
  3. ^ Kartogramm at the German Wikipedia.
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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Statistics Dictionary. A Dictionary of Statistics. Second edition revised. Copyright © Oxford University Press, 2008. All rights reserved.  Read more
Geography Dictionary. A Dictionary of Geography. Copyright © Susan Mayhew 1992, 1997, 2004. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Cartogram".  Read more