In applications where the geographic distribution of nongeographic data must be displayed, other graphic elements should be added to a map for that purpose.
Additional Information:
A display for radioactive control, for example, might superimpose plume tracks on a background of geographic coordinates, with supplementary annotation and/or coding to indicate track identification, speed, heading, altitude, etc. Alphanumeric characters might be added to a map to show data, but those will not aid a direct visual comparison across areas in the same way that graphic symbols can do. Moreover, alphanumeric data may be confused with labels and other kinds of annotation. For example, a symbol might be displayed in different sizes to indicate a particular measure in different localities, or small stacked bars might be superimposed on the different areas of a map to indicate the local distribution of some data measure.