Accessibility in Map Design

Last updated on 2026-04-12 | Edit this page

Overview

Questions

  • Why is accessibility important in cartography?
  • How do different types of color vision deficiency affect map reading?
  • How can we design maps that are readable for colorblind users?
  • What role do hue, saturation, and value play in accessible design?
  • Which color palettes work best in QGIS for accessible maps?

Objectives

  • Understand why accessibility matters in map design
  • Recognize major types of color vision deficiency (CVD)
  • Apply color-safe cartographic principles
  • Select accessible color palettes in QGIS
  • Test maps for readability across audiences

Why Accessibility Matters in Maps

Maps are communication tools.
If part of your audience cannot interpret your colors, your map fails to communicate effectively.

Accessible maps: - Reach wider audiences - Improve readability for everyone - Reduce misunderstanding and bias - Support inclusive science communication

Callout

Key Idea

Accessibility is not optional — it is part of good cartographic design.

Understanding Color Vision Deficiency (Colorblindness)

Color vision deficiency affects how some people distinguish colors.

Approximately: - ~8% of men - ~0.5% of women

experience some form of color vision deficiency.

Common Types of Colorblindness

1. Deuteranopia (Green-Blind)

Most common form.

People may confuse: - Green ↔︎ Red - Green ↔︎ Brown

2. Protanopia (Red-Blind)

Reduced sensitivity to red light.

People may confuse: - Red ↔︎ Green - Red appears darker

3. Tritanopia (Blue-Blind)

Rare.

People may confuse: - Blue ↔︎ Green - Yellow ↔︎ Violet

4. Achromatopsia (Monochromacy)

Very rare.

Little or no color perception.

Maps may appear nearly grayscale.

Discussion

Challenge

Why might a red-green choropleth map fail for many users?

Common Mapping Problems for Colorblind Users

Poor design choices include: - Red vs green comparisons - Similar lightness values - Too many hues with low contrast - Relying only on color to encode meaning

Example bad pairing: ❌ Red and green categories on same map

The Solution: Use Hue, Saturation, and Value Wisely

Hue

The color family (red, blue, green)

Avoid: - Red-green combinations - Blue-purple confusion in tritanopia

Saturation

Intensity or purity of color

Use: - Moderate saturation - Avoid oversaturated bright colors

Value (Lightness)

Most important for accessibility.

If colors differ in brightness, they remain distinguishable even if hue is unclear.

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Best Practice

When in doubt, vary lightness more than hue.

Designing Accessible Maps

Use More Than Color

Combine color with: - Patterns - Labels - Symbols - Line styles

Example: Instead of only red vs green, use: - Blue circles - Orange squares

These palettes work well across most users.

Sequential Data:

Best choices: - Blues - Viridis - Cividis - YlGnBu

Diverging Data:

Best choices: - Blue–Orange - Purple–Green (carefully tested)

Categorical Data:

Best choices: - ColorBrewer Set2 - Dark2 - Tableau palettes

Callout

Avoid Rainbow Palettes

Rainbow color ramps create misleading emphasis and poor accessibility.

Best QGIS Palettes for Accessibility

In QGIS, use built-in ramps such as:

Excellent Choices:

  • Viridis
  • Cividis
  • Plasma
  • Inferno
  • Blues
  • ColorBrewer Safe

Avoid:

  • Rainbow
  • Red-Green diverging ramps
  • Neon saturated ramps

How to Apply Accessible Palettes in QGIS

Step 1: Open Symbology

Right-click layer → Properties → Symbology

Step 2: Choose Color Ramp

Select: - Viridis - Cividis - Blues

Step 3: Preview Contrast

Check: - Are adjacent classes clearly distinguishable? - Do values differ in brightness?

Testing Your Map for Accessibility

Always test your design.

Tools:

  • QGIS Preview Modes
  • Color Oracle
  • Coblis Color Blindness Simulator

Ask:

Can someone distinguish categories without relying only on hue?

Accessibility Beyond Colorblindness

Remember: Accessibility also includes: - Readable font sizes - Clear legends - Sufficient contrast - Screen-reader compatible web maps

Example: Good vs Bad Design

Bad:

❌ Red-green choropleth with equal brightness

Good:

✅ Blue-orange palette with strong value contrast

Accessibility Checklist for Maps

Before publishing:

Final Takeaways

Accessible maps are: - Clearer - More inclusive - More professional

Good cartography means designing for all users.

Discussion
  • Have you seen maps that were difficult to read because of color?
  • How can accessibility improve scientific communication?