A topographic map tells you where things
are and how to get to them, whether
you're hiking, biking, hunting, fishing, or
just interested in the world around you.
These maps describe the shape of the
land. They define and locate natural and
manmade features like woodlands, waterways,
important buildings, and bridges.
They show the distance between any two
places, and they also show the direction
from one point to another.
Distances and directions take a bit of figuring,
but the topography and features of
the land are easy to determine. The topography
is shown by contours. These are
imaginary lines that follow the ground
surface at a constant elevation; they are
usually printed in brown, in two thicknesses.
The heavier lines are called index
contours, and they are usually marked
with numbers that give the height in feet
or meters. The contour interval, a set difference
in elevation between the brown
lines, varies from map to map; its value is
given in the margin of each map. Contour
lines that are close together represent
Natural and manmade features are represented
by colored areas and by a set of
standard symbols on all U.S . Geological
Survey (USGS) topographic maps.
Woodlands, for instance, are shown in a
green tint; waterways, in blue. Buildings
may be shown on the map as black
squares or outlines. Recent changes in an
area may be shown by a purple overprint.
A road may be printed in red or black
solid or dashed lines, depending on its
size and surface. A list of symbols is
available from the Earth Science
Information Center (ESIC).