5.2 Cartographic Design Principles

Key takeaways

• Cartographic design shares principles with graphic design, adapted to spatial constraints.
• Four principles dominate: hierarchy, balance, contrast, and simplicity.
• Great maps look inevitable but are the result of many small deliberate choices.

Introduction

A map is a designed artefact. It communicates under constraints — finite space, unalterable geography, a specific message. Cartographic design borrows liberally from graphic design but layers on spatial specifics. This lesson covers four principles you'll apply on every map you make.

1. Visual hierarchy

Every element on the page competes for attention. Hierarchy is the deliberate ordering of what should be seen first, second, third.

Tools:

• Size — bigger is louder.
• Contrast — high contrast draws the eye; low contrast recedes.
• Colour — saturated colours advance; muted colours recede.
• Typography weight — bold beats regular beats light.
• Position — top-left is prime real estate.

A well-designed map lets the reader absorb its message in under five seconds. If it takes longer, hierarchy is wrong.

2. Balance

Balance is visual weight distributed across the page. A title on the top-left, a legend on the bottom-right, and an inset on the bottom-left balance each other. A map with a heavy upper-left and empty lower-right feels off, even if you can't articulate why.

Balance doesn't mean symmetry — asymmetric layouts often feel more dynamic. But total visual weight should be approximately even across quadrants.

3. Contrast

Contrast is the difference between adjacent elements — in colour, value (lightness), size, or texture. Contrast makes features readable.

• Dark text on light background (or vice versa).
• Saturated data colour against muted base map.
• Bold borders around the main map frame.

Low-contrast maps feel washed out; high-contrast maps feel harsh. The goal is sufficient contrast to distinguish every element, no more.

4. Simplicity

"Perfection is achieved when there is nothing left to take away." Cartographers love this quote because cluttered maps are universal. Rules of thumb:

• Every element must earn its place.
• Round numbers on scale bars. "0–5 km" beats "0–4.73 km".
• Use 2–3 colours for most thematic maps; 5–7 maximum.
• Limit fonts to 1–2 families.
• Remove graticules at scales where they don't help.
• Never use 3D effects, drop shadows, bevels unless they serve the story.

Alignment

Align elements to invisible grid lines. Legend title aligns with map title. Scale bar aligns with legend. Source line aligns with page edge. Small alignment inconsistencies look unprofessional even when they're technically fine.

The repetition principle

Repeated visual patterns signal organisation. Repeating colours, fonts, line widths, and symbol shapes across similar elements helps the reader group and categorise. An inset map shares visual style with the main map so they're clearly related.

Proximity

Related elements belong together; unrelated elements apart. Put the legend close to the thing it labels, separated from unrelated elements. Put the data source line near the date — together they describe provenance.

Use of type (typography)

• Sans serif for modern, clean maps (Helvetica, Inter, Roboto).
• Serif for formal or historical maps (Minion, Caslon).
• Italic for water features, traditionally.
• Two families maximum. Pair them intentionally — e.g., a serif for titles, sans for labels.
• Never use Comic Sans, Papyrus, or Arial. That's not a joke.

Module 5.4 covers typography in maps in depth.

Use of colour

• Sequential ramps for ordered data (light → dark).
• Diverging ramps for data with a meaningful middle (below / above zero).
• Qualitative palettes for categories without order.
• Avoid rainbow ramps for ordered data — they're not perceptually uniform and alienate colour-blind readers.

Module 5.3 is a full lesson on colour.

Consistency across a map series

When producing multiple maps for the same report:

• Identical layouts (same title position, same scale bar size).
• Same colour ramp for the same variable.
• Same projection unless you have a reason to change.
• Same map scale where practical.

Inconsistent series force the reader to relearn the visual language with each map. Consistent series let them focus on the data.

The generosity principle

Design for a reader who's glancing, tired, or slightly drunk at a conference. If the map is still readable under those conditions, you've designed well.

Worked example: revising a map

A common exercise: take a flawed map and improve it. Typical revisions:

1. Shrink the title and reduce its font weight — it was dominating the map.
2. Mute the base map — it was competing with the thematic layer.
3. Switch from rainbow to viridis for the sequential colour ramp.
4. Simplify the legend — consolidate near-identical categories.
5. Align the scale bar and north arrow on a grid.
6. Make the data source line two pts larger so it's actually readable.
7. Add 10 mm margins on all sides to give the map room to breathe.

Seven small changes, enormous improvement.

You can do this revision exercise in Atlas as well as QGIS: duplicate a map, mute the base map, adjust the thematic layer, simplify the legend, and compare the two versions side by side. Browser-based tools are especially useful when you want quick feedback from non-GIS teammates before committing to a final layout.

Self-check exercises

1. Name four tools for establishing visual hierarchy on a map.

Size (larger draws more attention), contrast (high contrast emphasises, low recedes), colour (saturated advances, muted recedes), position (top-left is prime), and typographic weight (bold vs light). Each tool can be dialled up or down to rank elements by importance.

2. Why avoid the rainbow colour ramp for ordered data?

Rainbow ramps are not perceptually uniform — equal steps in the data don't correspond to equal steps in perception. They also fail for colour-blind readers (red/green confusion is common). Perceptually uniform ramps like viridis, magma, or the ColorBrewer sequential palettes produce more accurate readings.

3. You've been asked to design a 12-map report. What three visual choices should stay the same across all maps?

Colour ramp for the variable being mapped (same range, same classification breaks), projection and extent (to aid comparison), and layout template (title position, legend style, scale bar). Consistency across a series lets readers compare directly without re-learning the visual language each time.

Summary

• Hierarchy, balance, contrast, and simplicity are the four primary design principles.
• Align elements to an invisible grid; related elements stay near; repeat visual patterns.
• Typography and colour each deserve deliberate choices.
• Consistency across a map series is itself a design principle.

Further reading

• Tufte, E. — The Visual Display of Quantitative Information.
• Brewer, C. — Designing Better Maps.
• Kraak & Ormeling — Cartography: Visualization of Spatial Data.
• CartoCSS and Mapbox GL style specs for worked examples of cartographic rules in code.