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Maps & Spatial Thinking

Goal: Develop the mindset of a spatial analyst — looking at problems as questions about where, how far, what's nearby, and what's changing.

What you'll learn

  • The five spatial questions every GIS project answers
  • How to read a map critically
  • The map design vocabulary you need (scale, projection, legend, etc.)

The five spatial questions

Every GIS project boils down to one of these:

Question Example
Where is something? Where are the food deserts in Atlanta?
What is at a location? What is the land cover at this coordinate?
How far between two things? How far is each school from the nearest park?
What's near something? What businesses are within a 10-min drive?
What's changed? How has urban sprawl changed since 2000?

When someone asks you a vague question, your job is to rephrase it into one of these five forms. That single skill is most of the job.

Reading a map critically

A good map answers a question. A bad map confuses you. Train yourself to spot:

flowchart LR
    A[Title] --> B[What question does it answer?]
    C[Legend] --> D[What do the colors/symbols mean?]
    E[Scale bar] --> F[How big is this area?]
    G[North arrow] --> H[Orientation]
    I[Source] --> J[Who made it? When? With what data?]
    K[Projection] --> L[Why does it look that shape?]

The 6-element checklist

Every professional map should have:

  1. Title — what question is being answered
  2. Legend — what the symbols mean
  3. Scale bar — distance reference
  4. North arrow — orientation
  5. Source / date — credibility
  6. Projection note — accuracy reference

More on this in Cartography.

Scale matters

Zoom level changes everything.

  • At city scale, a road is a line.
  • At block scale, the same road is a polygon (it has width, sidewalks, lanes).
  • At state scale, the road may not even be visible.

A map's scale defines what level of detail is appropriate. Don't show census tracts on a national map. Don't show states on a neighborhood map.

Spatial autocorrelation (preview)

"Everything is related to everything else, but near things are more related than distant things." — Tobler's First Law of Geography

This is the philosophical foundation of GIS. Houses near a park are more similar in price than houses far apart. Crime clusters. Disease clusters. Wealth clusters.

We'll come back to this in Spatial Analysis.

Common map types

  • Reference map

    Shows where things are (e.g., a road map, topographic map). Goal: navigation.

  • Thematic map

    Shows a single variable (population, income, rainfall). Goal: understanding.

  • Choropleth map

    Polygons colored by value (a thematic map). The classic "income by county".

  • Heatmap / density

    Continuous surface from points (crime hotspots, accidents).

  • Dot map

    One dot = N units. Great for population.

  • Flow map

    Lines showing movement (migration, trade, traffic).

Practice

Map critique

Pick any map from a news article. Answer these:

  1. What question is this map trying to answer?
  2. Does it have all 6 essential elements?
  3. What's the data source?
  4. Is the color scheme appropriate?
  5. At this scale, would a different visualization (chart, table) be better?

If you can confidently answer those, you're already thinking like a GIS analyst.

Next up

→ Coordinate Systems & Projections — the most important topic in GIS.