Read thematic maps
The idea
Thematic maps emphasize a variable such as rainfall or population. Read the title, legend, units, date, and geographic boundaries. Total counts and rates answer different questions. Color intensity may reflect a chosen classification rather than a natural boundary.
Worked example
A large region may have many residents but low population density. A map of total population cannot be read as if it shows people per square kilometer.
Another application
A region with 100,000 people across 1,000 square kilometers has density 100 people per square kilometer. A region with 50,000 people across 100 square kilometers has density 500: fewer people but higher density.
A common misunderstanding
A shaded map can exaggerate or minimize differences through its category breaks. Always examine the legend and denominator.
Try it yourself
Compare a map of population totals with a density map. Explain one place where they convey different impressions and why.
Check your understanding
Are population and population density the same measure?
Reveal the explained answer
No. Density divides population by area.