Topographic
Maps
TOPOGRAPHIC
MAPS
What are topographic maps?
• Topographic mapsmaps that show
changes in elevation
of Earth’s surface
• Elevation- distance
above sea level.
• Also show mountains,
rivers, forests and
bridges
Contour Lines
• Contour lines- connects points of equal
elevation.
One Island….Two Views
One Island…Two Views
Identify the Elevation
What is a contour interval?
• Contour interval- the difference in
elevation between two side by side
contour lines
What is the
difference in
elevation
between
these two
lines?
What are index contours?
• Index Contours- contour lines that have
marked elevations.
• Can use them to find the contour interval
Index
Contours
Finding the Contour Interval
1. Find the index contours.
2. Determine the elevation
difference between the two
index contours
800 m – 700m = 100 m
3. Count the number of spaces
between the 2 index
contours.
5
4. Divide the elevation
difference between the 2
index contours by the
number of spaces.
100 m / 5 = 20 m.
Scale
• Scale is the
relationship
between
horizontal
distance on the
map and distance
on the ground.
Three types of scale
Three types of scale
Three types of scale
Do Worksheet 1-6
CONTOUR MAPPING RULES
1. A contour line represents a single equal
elevation, all points on the contour line have the
same elevation.
2. Contour lines do not cross other contour lines.
3. Where one closed contour line surrounds
another, the inner contour line represents the
higher elevation.
Which line has
the higher
elevation?
4. Every 5th contour line is darker and has the
elevation marked. These are index contours.
What is slope?
• Slope- change in
elevation over a given
horizontal distance
• Formula for slope
Slope = change in elevation
horizontal distance
Which hill has a steep slope?
Gentle slope?
5a. On a contour map, closely spaced lines
indicate a steep slope.
5b. Widely spaced lines indicate a gentle slope
5c. Uniformly spaced lines indicate a uniform
(constant) slope.
Notice that the contour lines for each are the same distance apart in
each picture. There is the same change in elevation for each given
distance.
Comparing Slope
6. A contour line that closes within the limits of a
map indicates a hill, ridge or plateau.
6a. Highest possible elevation of a hill is just below
the value of the next contour line that would be
drawn.
The last contour line drawn is 220 m. The next line would be 240
m. Since there is no 240 m line, the hill cannot be higher than
239 m.
7. Depressions are shown by small marks
(hachures) pointing inward off the contour line.
Elevation of the depression would be
less than 140 m.
8. Where a contour line crosses a stream or valley,
the contour bends to form a “V” to point upstream.
Exit Card
Without looking at your notes, write two
things you learned today.
Write one question you have about
topographic maps. It can be something
that confused you or something you’d like
more information about.