Topographic Maps
Topographic Maps
A topographic map of part of Ithaca
Topographic Maps
• Maps of an elevation field
• Show elevation by contour lines
• Also show other natural and
man-made features by using
symbols
HOW TO READ
TOPOGRAPHIC MAPS
1. Contour lines – lines the connect points of
equal elevation
• Contour Lines close together – Steep slope
• Contour Lines far apart – Gentle slope
2. Contour Interval
 The contour interval on this map is 20?
What do you think is a contour interval?
Contour Interval
Change in elevation in between two
consecutive contour lines
Usually listed in key or legend
If you are at sea level, your elevation is 0.
The contour line for the coastline is 0.
3. Index Contour Line
• The Index Contour lines on the map below
are the 700 and 800 lines
Why do you think they are darker?
Index Contour Lines
• Every 4th or 5th line that is thicker or bolder
• Line is labeled with the elevation
• Helps to read the map
Index contour lines
are placed every 50
units on this map
 What is the spacing
of Index Contours on
this map?
 What is the contour
interval?
4. Hills
• How is a hill depicted on a topographic
map?
Hills
• Closed contours in a circle or elliptical
(oval) shape
• “Bulls eye”
5. Depressions
• The opposite of a hill is a depression
which is a low point in the ground. They
are represented by hachure lines.
Describe what a
hachure line looks
like.
Feathered line or
a line with hash marks
5. Hachured Lines
• Does the elevation go up or down when
you see the hachured lines? down
• The first depression line is going to the
same elevation as the closest contour
________
line
6. Benchmark - EXACT Elevation
Indicated by a BM or X on a
topographic map
• What is the exact elevation of the
benchmark on this map?
2919 feet
7.
Streams always flow Downhill –
from higher elevation to lower
elevation
Can a stream flow
northward? Yes
N
What direction is this stream flowing?
South
N
Describe what the contour lines look
like when they are crossing a stream?
Contour lines point in the opposite
direction the stream is flowing!
Streams always
flow in the
opposite direction
the V or U is
pointing.
8. Maximum Elevation of a Hill
Steps to follow:
1. Count up the contour lines using the
contour interval.
2. Pretend that there is one more contour
line at the top of the hill (imaginary line).
3. Subtract 1
• How is the highest possible elevation?
Highest contour line = 40
Pretend one more so
that would be 50
Subtract 1
50 – 1 =
Maximum elevation of hill is 49
9. Minimum Elevation of a
Depression
Steps to follow:
1. Count down the contour lines using the
contour interval.
2. Pretend that there is one more contour
line at the bottom of the depression
(imaginary line).
3. add 1
Map Scales
• The relationship between distance as
measured on a map and the actual distance
on Earth’s surface
Types of Map Scales
a. Verbal Scale – 1 inch = 20 miles
b. Bar Scale
One Mile
Types of Map Scales
c. Ratio Scale -
One of any unit on this map represents
24,000 of the same unit on Earth’ s surface.
Ex, one inch would equal 24,000 inches on
the Earth
• Maps often give you more than one way to
measure distance
Represents parts of
one mile, ex: one tenth
of a mile
Represents one
mile on the map
One kilometer