Thematic Map
Definition
A thematic map emphasizes a specific subject—population density, income, land cover, disease rates—rather than general reference detail. Design choices include map type (choropleth, proportional symbol, dot density, isopleth), classification scheme (quantiles, natural breaks, equal interval), color ramps, and annotation. Good thematic maps consider data uncertainty, normalized denominators (per capita/area), and accessibility for color vision.
Application
Policy makers explore inequalities; NGOs communicate program reach; scientists share model outputs; and journalists explain complex stories quickly. Thematic maps are powerful when paired with concise explanations and sources.
FAQ
How do you choose a classification scheme responsibly?
Select a method that supports interpretation and avoids visual manipulation; test multiple schemes and disclose the choice to prevent cherry-picking.
When is a choropleth inappropriate and what alternatives exist?
Choropleths mislead when polygon sizes vary greatly or data represent counts. Use proportional symbols, dasymetric mapping, or hex-binning instead.
How should uncertainty be shown?
Use transparency, hatching, or side panels with confidence intervals so readers understand reliability alongside the theme.
What accessibility practices improve readability?
Color-blind-safe palettes, adequate contrast, descriptive legends, and avoiding red–green critical distinctions without cues.