What is a defining feature of an isoline map?

• A. It uses color shading to represent data.
• B. It uses dots to indicate occurrences.
• C. Lines that connect equal values.
• D. It shows data only at discrete locations with dots.

Answer: (C)

Isoline maps are defined by lines that connect points with the same value. These contour-like lines create a continuous surface showing how the data changes across space, so you can see gradual gradients rather than just isolated points. For example, contour lines on a topographic map connect places of equal elevation, and isotherms connect equal temperatures.

Color shading, as in a choropleth map, uses different colors to represent value ranges in areas rather than drawing lines to link equal values. Dots indicating occurrences describe a dot map, which marks individual events or points. Showing data only at discrete locations with dots also points to a dot or point map rather than a continuous surface.