VISUAL VOCABULARY / 07

Map Atlas / Visual Map Vocabulary

Compare choropleths, proportional symbols, contour lines and flow maps using the same fictional region.

Original fictional boundaries and data, not real geography, statistics or transportation.

Choropleth versus symbols

Color encodes rates rather than totals.

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Compare

Proportional-symbol map

Region A: 12 / 100 = 12%

Data and units — A:12/100=12%, B:24/400=6%, C:34/200=17%, D:48/600=8% · Legend: 6%, 10%, 15% · contour interval:20 · flow volumes:5, 15, 9

Appearance and name

Choropleth map

Appearance and name: Shade each region by a normalized rate.
Difference: Color encodes rates rather than totals.
When to use: Compare rates across regions.
Limits: State the denominator and breaks; a color boundary is not a physical jump.

Creation brief

Choropleth map. Shade each region by a normalized rate. Compare rates across regions. State the denominator and breaks; a color boundary is not a physical jump.

Proportional-symbol map

Appearance and name: Size circles by quantity using area.
Difference: Circle area represents totals; use color to compare rates.
When to use: Compare counts and totals.
Limits: Circle area, not radius, corresponds to quantity.

Creation brief

Proportional-symbol map. Size circles by quantity using area. Compare counts and totals. Circle area, not radius, corresponds to quantity.

Contour map

Appearance and name: Connect equal elevations with contours.
Difference: Contours describe continuous elevation, not regional statistics.
When to use: Read slopes and terrain.
Limits: Label the contour interval; not a routing map.

Creation brief

Contour map. Connect equal elevations with contours. Read slopes and terrain. Label the contour interval; not a routing map.

Flow map

Appearance and name: Show movement between places with direction and line width.
Difference: Flows connect origins and destinations rather than just locating quantities.
When to use: Show directional movements and relative volumes.
Limits: Width reflects an illustrative volume, not travel time or actual roads.

Creation brief

Flow map. Show movement between places with direction and line width. Show directional movements and relative volumes. Width reflects an illustrative volume, not travel time or actual roads.

Coverage

Compare	Not yet included
Choropleth map	Dot-density
Proportional-symbol map	Cartogram
Contour map	Hillshade
Flow map	Network routing

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