74 THE GEOGRAPHIC
AND CARTOGRAPHIC FRAMEWORK
to visualize, the scale is often converted to words. Thus, 1/1,000,000 becomes 1 inch
represents about 16 miles or 1 centimeter represents 10 kilometers; 1/24,000 becomes
1 inch represents 2,000 feet or 1 centimeter represents 240 meters. This is called a
verbal scale or a
word scale, in which the figures may be rounded off. For example,
1:1,000,000 is actually 1 inch represents 15.782828 miles but would be rounded to
either “about 15 3/4 miles” or “about 16 miles.” Because verbal scales are often used
as
a rough estimate, such rounding doesn’t usually present a problem.
A third way of expressing scale is visually or graphically. A line is drawn at the
same scale as the map and divided into units. Thus, for a 1:24,000 map, a one-inch
line represents 2,000 feet and 1/2 inch represents 1,000 feet. This kind of scale is
called a
graphic scale,
bar scale, or
linear scale.
The terms “large scale” and “small scale” are often used and frequently con-
fused. A large-scale map shows a small area in great detail; a small-scale map shows
a large area but with little detail. Thus, a world map shown on an atlas page is a
small-scale map and a city map appearing in the same atlas is a large-scale map. The
terms large scale and small scale are relative terms; there is no specific dividing point
for large and small scales, although some map series such as USGS topographic maps
will have set scales for large, medium, and small scales
for the series. The larger the
denominator of the RF, the smaller the scale. The scale 1:1,000,000 is smaller than
the scale 1:500,000. This is the same as any fraction: 1/6 of a pie is smaller than 1/4
of a pie. Figures 5.2a, 5.2b, and 5.2c show the same general area at three different
scales. Note
the size of the area shown, and the amount of detail.
