Editing Cartogram (section)

{{Short description|Map distorting size to show another value}}
{{Broader|Thematic map}}
{{Distinguish|Cartography}}
[[File:Global population cartogram.png|thumb|upright=1.35|Mosaic cartogram showing the distribution of the global population.
Each of the 15,266 pixels represents the home country of 500,000 people – cartogram by [[Max Roser]] for [[Our World in Data]]]]

A '''cartogram''' (also called a '''value-area map''' or an '''anamorphic map''', the latter common among German-speakers) is a [[thematic map]] of a set of features (countries, provinces, etc.), in which their geographic size is altered to be  [[Proportionality (mathematics)|directly proportional]] to a selected variable, such as travel time, [[population]], or [[gross national income]]. Geographic space itself is thus warped, sometimes extremely, in order to visualize the distribution of the variable. It is one of the most abstract types of [[map]]; in fact, some forms may more properly be called [[diagram]]s. They are primarily used to display emphasis and for analysis as [[Nomography|nomographs]].<ref name="tobler2004">{{Cite journal | last = Tobler | first = Waldo | title = Thirty-Five Years of Computer Cartograms | journal = Annals of the Association of American Geographers | volume = 94 | issue = 1 | pages = 58–73 | date = March 2022 | jstor = 3694068 | doi=10.1111/j.1467-8306.2004.09401004.x| citeseerx = 10.1.1.551.7290  | s2cid = 129840496 }}</ref>

Cartograms leverage the fact that size is the most intuitive [[visual variable]] for representing a total amount.<ref name="bertin">Jacque Bertin, ''Sémiologie Graphique. Les diagrammes, les réseaux, les cartes''. With Marc Barbut [et al.]. Paris : Gauthier-Villars. ''Semiology of Graphics'', English Edition, Translation by William J. Berg, University of Wisconsin Press, 1983.)</ref> In this, it is a strategy that is similar to [[proportional symbol map]]s, which scale point features, and many [[flow map]]s, which scale the weight of linear features. However, these two techniques only scale the [[map symbol]], not space itself; a map that stretches the length of linear features is considered a linear cartogram (although additional flow map techniques may be added). Once constructed, cartograms are often used as a base for other thematic mapping techniques to visualize additional variables, such as [[choropleth map]]ping.