Maps classified by value ranges provide a visual hierarchy of geographic phenomena through variations in color intensity. Typically, this is achieved using a graduated color ramp, ranging from white, which represents the lowest values, to darker shades, which represent the highest values for the phenomenon being analyzed.
Population by Microregion
Figure 1 presents population data by microregion. The darker colors indicate areas with larger populations.
Figure 1 – Population by Microregion
Depending on the map scale, however, the representation shown in Figure 1 may not be the most appropriate choice. Very small polygons may become difficult to visualize, while larger polygons tend to attract more attention and may create the impression that the values are higher or that the phenomenon is more significant simply because of their larger geographic area.
Population Represented with Proportional Symbols
A more suitable alternative in many cases is to represent population using proportional symbols, as illustrated in Figure 2.
Figure 2 – Population Represented with Proportional Symbols
Proportional symbol maps allow users to compare values more effectively because the size of the symbol reflects the magnitude of the phenomenon, reducing the visual bias caused by differences in polygon area.
When choosing a mapping technique, it is important to consider the nature of the data, the geographic scale, and the message that the map is intended to communicate.