Geography Reference
In-Depth Information
When gray tones are used in cartography, the general rule of thumb is “the darker the gray
tone, the greater the value of whatever is being mapped.” Accordingly, and as seen in Figure
5-3c, the lightest shade indicates the lowest-lying land, while deeper shades signify progress-
ively higher elevations.
While spot heights and contour lines identify the precise elevations of precise locations, shadings
refer to a range of elevations over an area. Thus, the lightest gray tone on Figure 5-3b signifies land
that is anywhere between sea level and 100 feet above sea level.
But that's just this one map. On a different map, the same gray tones may mean something
very different. Similarly, a light brown color may signify a particular elevation on one map,
butaverydifferentelevationonadifferentmap.Remember:Alwayscheckthelegendtomake
sure of the meaning of particular shades.
Using Symbols to Tell the Story
As highlighted by the discussion of topography, maps commonly show things by means of point, line,
and/or area symbols. Each category, in turn, may display either qualitative or quantitative informa-
tion. That is, each can simply show where something is located, or how much of something exists at
a particular location or over a particular area.
Point symbols
Point symbols are used to locate discreet phenomena on Earth's surface. Most fall within one or more
of the following categories.
Nominal icons
are tiny likenesses or symbols they name (hence, nominal) and indicate the
locations of particular landscape features. Thus a tiny black dot (•) may be used to symbolize
a residence while a cross (†) may be used to locate a cemetery. Whatever the symbol, the car-
tographer must explain its meaning in the map's legend.
