Darker cells mean a higher score for this topic on that metric.
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Quick answers
When should I pick Choropleth story maps?
When the story is: regional comparisons, civics assignments, territory KPIs.
When should I avoid Choropleth story maps?
Skip it in cases like: raw counts without normalizing by population or area.
Who invented or popularised it?
Baron Charles Dupin (1826); modern TopoJSON + D3 geo pipelines
What does it encode?
color of administrative regions mapped to a quantitative rate
Is it OK in ads?
Yes if one claim is visible at a glance in Meta, Google and retail print; otherwise link to a full figure.
Will a teacher accept it?
Yes for lab reports and poster boards if axes, units and a source line are present.
Choropleth story maps encodes values as color of administrative regions mapped to a quantitative rate. Baron Charles Dupin (1826); modern TopoJSON + D3 geo pipelines.
In reports, ads and assignments it fits regional comparisons, civics assignments, territory KPIs. Skip it when raw counts without normalizing by population or area.
Software
- TopoJSON — Compact topology for boundary files - BSD-3-Clause. · BSD-3-Clause · github.com/topojson/topojson
- d3-geo — Projections and path generators for maps. · ISC · github.com/d3/d3-geo
- Leaflet — Lightweight interactive maps when you need pan/zoom. · BSD-2-Clause · github.com/Leaflet/Leaflet
- d3-scale-chromatic — Sequential and diverging fills that beat rainbow maps. · ISC · github.com/d3/d3-scale-chromatic
- ColorBrewer — Cartographic palettes designed for choropleths. · Apache-2.0 · github.com/axismaps/colorbrewer
Exports
- Exports 1 — SVG
- Exports 2 — PDF
- Exports 3 — EMF/SVG into slides (no screenshots)
- Exports 4 — SVG for web, PDF for print
Accessibility
- Accessibility 1 — Never hue alone. Stack pattern, label and position.
- Accessibility 2 — 4.5:1 for text, 3:1 for large marks.
- Accessibility 3 — Short alt text on the chart; numbers also as an HTML table.
- Accessibility 4 — Motion only as emphasis. Honour prefers-reduced-motion.
Choropleth story maps: honour color of administrative regions mapped to a quantitative rate, and switch when raw counts without normalizing by population or area.