Choropleth map

Australian Census 2011 demographic map - Australia by SLA - BCP field 2715 Christianity Anglican Persons

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Countries by mean wealth per adult in 2018

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Choropleth Map

Choropleth-density

Choropleth map is a type of thematic map used for representing spatial data through various shading patterns or colors in predefined areas. These maps are commonly used to depict density, percentage, or average values of a particular geographic area, making them a valuable tool in geography, statistics, public health, and socio-economic analysis. The term "choropleth" comes from the Greek words "choro" meaning "area" or "region" and "pleth" meaning "a value", thus choropleth map translates to "a map of values over areas".

Overview

A choropleth map is distinguished by its use of color to represent the intensity or magnitude of a particular attribute, such as population density, poverty rate, or election results, across different regions. The geographic area is usually divided into predefined units like countries, states, counties, or districts. Each unit is then colored or shaded according to the data value it represents, allowing for easy visual comparison across regions.

Construction

The construction of a choropleth map involves several key steps:

1. Data Collection: Gathering accurate and relevant data for the attribute to be mapped.
2. Data Classification: Dividing the data into categories or classes. Common classification methods include equal intervals, quantiles, natural breaks (Jenks), and standard deviations.
3. Color Selection: Choosing a color scheme that effectively represents the range of data values. Sequential, diverging, and qualitative are the three main types of color schemes used.
4. Map Creation: Applying the color scheme to the geographic units based on their data classification.

Uses

Choropleth maps are widely used in various fields for different purposes:

• In public health, to show the distribution of health-related statistics such as disease incidence or vaccination rates.
• In economics, to illustrate economic indicators like GDP per capita or unemployment rates across different regions.
• In political science, to represent election results, showing which areas voted for which candidate or party.
• In environmental science, to display data on climate variables, pollution levels, or land use patterns.

Advantages and Limitations

Advantages:

• Choropleth maps are relatively easy to understand, making them accessible to a broad audience.
• They are effective for showing the geographical distribution of data and identifying patterns or trends across different regions.

Limitations:

• They can be misleading if the areas of the geographic units vary significantly, as larger areas may appear more important regardless of their actual value.
• The choice of classification method and color scheme can greatly influence the map's interpretation.
• They do not represent data at a point level and are not suitable for showing precise locations of phenomena.

See Also

• Thematic map
• Cartography
• Geographic information system (GIS)
• Data visualization