Dot Density

Question 1

When to use dot density maps

Answer 1

visualize general spatial distribution
Use discrete or raw data
One-to-Many mapping

Question 2

When not to use dot density

Answer 2

1) attributes have small range or uniform distribution
2) attributes have extremely large range

Question 3

The effect of changing dot value and dot size

Answer 3

Small dot + Small value = more accurate
Large dots + large value = more crude
Balance of generalization and accuracy

Question 4

Counting down

Answer 4

rounding down in dot values
Remainders are not mapped
4,500 gets rounded to 4,000
Causes underestimation bias

Question 5

Proper dot placement

Answer 5

Dots should be placed at the approximate center of gravity of the elements they represent

Question 6

Areal mean

Answer 6

center of real distribution
like the center of the dots across a polygon rather than the center of the polygon

Question 7

Dot patter

Answer 7

should be irregular
try not to follow enumeration unit lines

Question 8

Legend element of a dot density map

Answer 8

Statement of unit value of dot
At least 3 squares illustrating different densities
Ancillary text clarifying randomization and enumeration unit

Question 9

Issues with dot density map

Answer 9

Not intended for exact measurement
Readers tend to overestimate values
“Accurate” representation of the distribution is subjective