# Topographic maps TeacherWeb by benbenzhou

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```									Maps as Models of the Earth
TOPOGRAPHIC MAPS
Topographic Maps
• One of the most widely used maps is called a
topographic map, which shows the surface
features of Earth.

• topography the size and shape of
the land surface features of a region

• elevation the height of an object above sea
level
Elevation on Topographic
Maps
• On topographic maps, elevation is shown by
using contour lines.
• contour line a line that connects points of
equal elevation on a map
• The difference in elevation between one
contour line and the next is called the contour
interval. The contour interval is selected
based on the relief of the area being mapped.
Elevation on Topographic
Maps
• relief the difference between the
highest and lowest elevations in a given
area
• Every fifth contour line is darker than
the four lines one either side of it. This
index contour makes reading elevation
easier.
Landforms on Topographic
Maps
• The spacing and direction of contour lines
indicate the shapes of the landforms
represented on a topographic map.
• Closely spaced contour lines indicate that the
slope is steep.
• Widely spaced contour lines indicate that the
land is relatively level.
Landforms on Topographic
Maps, continued
• A contour line that bends to form a V shape
indicates a valley. The bend in the V points
toward the higher end of the valley; this V
points upstream, or in the direction from
which the water flows, if there is a stream.
• Contour lines that form closed loops indicate
a hilltop or a depression. Closed loops that
have short straight lines perpendicular to the
inside of the loop indicate a depression.
Topographic Maps,
continued
The diagram shows how topographic maps
represent landforms.
Topographic Map Symbols
Topographic Map Symbols
• Symbols are used to show certain features on
topographic maps.

• Symbol color indicates the type of feature.
Constructed features, such as buildings, are
shown in black. Highways are shown in red.
Bodies of water are colored blue, and
forested areas are colored green.
Index Contour, Contour
Interval, and Relief
Contour Lines
• Topographic maps use contour lines to
indicate the shape and elevation of these
landscape features because it is difficult, as
we have already discovered, to show three-
dimensional objects, like hills and valleys, on
a two-dimensional surface, like a map.
• Contour lines are lines that connect
the location of equal levels of
elevation.
Contour Lines cont…
• If you are looking at a hill that is
symmetrical, the contours will be almost
round and become smaller and smaller
towards the center of the hill as
elevation increases
Contour Lines cont…
• If you are showing a hill with two peaks,
your contour lines may look like this:
Contour Interval and Relief
• Contour Interval is the difference in
elevation between one contour line and the
next.
• Relief is the difference in elevation between
the highest and lowest points of the area
being mapped. Relief is used to determine
the contour interval of a map.
Contour Intervals
• When terrain is flat, such as in prairie
regions, contour intervals can have
small values or increments, such as
one or two meters so
that even slight
changes in the elevation of the
landscape can be detected.
Contour Intervals and
Distance
• In mountainous or very hilly regions, such as
the Rocky Mountains that border Alberta and
British Columbia or the Laurentian Mountains
in Quebec, contour intervals usually
represent a greater vertical distance, such as
fifty meters, so that the map isn't
completely covered in contour
interval lines.
The Rocky Mountains
Contour Intervals
• Contour intervals that are closer together mean
that there is a greater change in elevation over a
shorter distance.

Mount Rainier located in Mount Rainier National
Park, Washington, and its contour lines
Contour Lines

• Contour lines showing a steep and
shallow gradient
Slope
• Another way of defining the change in elevation
over a distance is to describe the slope.
• Topographic maps are useful tools in
determining just how steep the land is, or how
"fast" it rises or falls. Slope can be expressed in
three ways: as a fraction, or ratio, referred to
as a gradient; as a percentage, rise divided by
the run multiplied by 100; and, as an angle
expressed in degrees from the horizontal.
Spacing of Contour Lines
• The spacing of contour lines indicate
slope. Contour lines that are close
together show a steep slope. Contour
lines that are far apart show a gentle
slope.
Index Counter
• An index contour is a darker, heavier
line that is usually every fifth line and
that is labeled by elevation.
Reading a Topographic Map

• Topographic maps use symbols to
represent parts of the Earth’s surface.
Colors are also used to represent
features.
• Cities and towns are pink, bodies of
water are blue, and wooded areas are
green
Golden Rules
• Contour lines never cross. All points
along a contour line represent one
elevation
Golden Rules cont…
• The spacing of contour lines depends
on slope characteristics. Contour lines
that are close together show a steep
slope.
Golden Rules cont…
• Contour lines that cross a valley or
stream are V shaped. The V points
toward the area of highest elevation. If
a stream or river flows through the
valley, the V points upstream.
Golden Rules cont…
• The tops of hills, mountains, and
depressions are shown by closed
circles. Depressions are marked with
short, straight lines inside the circle that
point down slope to the depression.
Topographic Map
Breakdown of Areas of
Woodland
Breakdown of topographic
features including Contour Lines
Breakdown of features that are added from
aerial photographs and other sources, but
are not field checked.

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