Dot distribution map
A thematic map using dots to show spatial distribution.
A dot distribution map (or dot density map or dot map) is a type of thematic map that uses point symbols to visualize the geographic distribution of a large number of related phenomena. It relies on a visual scatter to show spatial patterns, especially variances in density. The dots may represent actual locations of individual phenomena or be randomly placed in aggregation districts to represent a number of individuals.
- type
- Thematic map
- field
- Cartography, epidemiology, spatial analysis
Lore & Background
The idea of using dots to show relative density emerged during the Industrial era of England and France in the 1830s and 1840s, enabled by increasing statistical data. This map used the same technique practiced for two centuries: dots randomly spread across each district.
Reader's Guide
Dot distribution maps are significant for their ability to visualize spatial patterns and density intuitively. The technique has two main types: one-to-one maps showing individual occurrences, and one-to-many maps using representative dots from aggregate data. Geographic information systems have automated dot placement, though results are often less satisfactory than manual maps. Recent advancements include dasymetric mapping, scaling dot rates at different zoom levels, and temporal animation.
Did You Know?
- Dot maps are a type of unit visualization that rely on a visual scatter to show spatial patterns, especially variances in density.
- A hybrid technique emerged in early 20th century maps using representative dots in rural areas with proportional circles for major cities.
Frequently Asked Questions
What exactly is a dot distribution map?
It is a thematic cartographic technique that plots individual point symbols across a map to reveal how a particular phenomenon is spread geographically. Rather than shading whole regions, it depends on the visual clustering or scattering of dots to communicate density patterns.
What role does the dot distribution map play in cartography?
It provides a way to visualize the spatial spread of many individual events or people without resorting to choropleth shading. Dots can either mark true point locations or be distributed randomly within administrative districts to stand in for a count of occurrences.
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