Since maps are a greatly reduced version of the real-world, objects cannot be depicted in their true shape or size. Therefore, a set of symbols is devised to represent real-world objects. There are two major classes of symbols:
Replicative symbols are designed to look like their real-world counterparts; they represent tangible objects, such as coastlines, trees, railroads, and houses. Abstract symbols usually take the form of geometric shapes, such as circles, squares, and triangles. They are traditionally used to represent amounts that vary from place to place, such as population density, amount of rainfall, and so forth. (Dent, 1985).
Both replicative and abstract symbols are composed of one or more of the following annotation elements:
These basic elements can be combined to create three different types of replicative symbols:
- plan—formed after the basic outline of the object it represents. For example, the symbol for a house might be a square, because most houses are rectangular.
- profile—formed like the profile of an object. Profile symbols generally represent vertical objects, such as trees, windmills, oil wells, and so forth.
- function—formed after the activity that a symbol represents. For example, on a map of a state park, a symbol of a tent would indicate the location of a camping area.
Symbols can have different sizes, colors, and patterns to indicate different meanings within a map. The use of size, color, and pattern generally shows qualitative or quantitative differences among areas marked. For example, if a circle is used to show cities and towns, larger circles would be used to show areas with higher population. A specific color could be used to indicate county seats. Since symbols are not drawn to scale, their placement is crucial to effective communication.
Use Symbol gallery and the symbol library to place symbols in maps.