Multivariate map

A bivariate map or multivariate map is a type of thematic map that displays two or more variables on a single map by combining different sets of symbols. Each of the variables is represented using a standard thematic map technique, such as choropleth, cartogram, or proportional symbols. They may be the same type or different types, and they may be on separate layers of the map, or they may be combined into a single multivariate symbol. The typical objective of a multivariate map is to visualize any statistical or geographic relationship between the variables. It has potential to reveal relationships between variables more effectively than a side-by-side comparison of the corresponding univariate maps, but also has the danger of Cognitive overload when the symbols and patterns are too complex to easily understand. The first multivariate maps appeared in the early Industrial era (1830-1860), at the same time that thematic maps in general were starting to appear. An 1838 booklet of maps produced by Henry Drury Harness for a report on Irish railroads included one that simultaneously showed city populations as proportional symbols and railroad traffic volume as a Flow map. Charles Joseph Minard became a master at creating visualizations that combined multiple variables during the 1850s and 1860s, often mixing choropleth, flow lines, proportional symbols, and statistical charts to tell complex stories visually. Multivariate thematic maps found a resurgence starting in the middle of the 20th Century, coinciding with the scientific turn in geography. George F. Jenks introduced the bivariate dot density map in 1953. The first modern bivariate choropleth maps were published by the U.S. Census Bureau in the 1970s. Their often complex patterns of multiple colors has drawn acclaim and criticism ever since, but has also led to research to discover effective design techniques. Starting in the 1980s, computer software, including the Geographic information system (GIS) facilitated the design and production of multivariate maps.

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Concepts associés (2)

Multivariate map

Cartogramme

vignette|Cartogramme de surface représentant la répartition de la population dans les états membres de l'UE (mars 2008). vignette|Cartogramme des listes en tête au premier tour par canton des élections régionales françaises de 2015. Un cartogramme est une carte pour laquelle une variable thématique, comme la population ou le PIB, remplace la surface des territoires représentés. La géométrie de l'espace de la carte est déformée afin de se conformer aux informations relatives à la variable représentée.