Drawing features to show quantities

Quantity attributes are always numeric. The numbers represent counts, amounts, rates, or measures.

 

Quantity Type

Layer Name

Attribute

Attribute Values

Count

 

Cities

Population
  • 1,009
  • 29,577
  • 134,528

Amount

 

Sales territories

Revenue (dollars)
  • 1,492.95
  • 3,056.28
  • 4,918.18

Rate

 

Counties

Literacy rate (percent)
  • 52
  • 66
  • 82

Measurement

 

Wells

Depth (meters)
  • 124.3985
  • 298.663
  • 527.08

 

Feature quantities are typically represented on a map by creating groups of features with similar values (classes) and assigning a different symbol to each class. However, even though the symbols are different, they usually change gradually from one class to another, forming a series. Graduated size and graduated color are the two most common ways to symbolize quantities.

Drawing features using symbols in a graduated series permits map readers to visualize geographic distribution patterns in quantity data. For example, if a map is drawn with colors ranging from yellow to orange to red, red areas can quickly be interpreted to represent greater values than yellow ones. Likewise, it is intuitive that smaller symbols represent smaller quantities than larger symbols.

 

Map of western European country population

 

The countries in this map are displayed with graduated shades of green. The darker the shade, the greater the country's population

 

When choosing graduated colors, it is important to be aware of common color associations that people make. People will easily understand a temperature map drawn with blue symbols for cold and orange for warm; the same map symbolized the opposite way would be frequently misinterpreted.