Guided Notes
Topographic Maps
Map scale
Straight line distance
Curved line distance
Rules of Isolines
Contour Lines
Hachured Lines
Possible elevations
Slope & Gradient
Direction of River Flow
Topographic Profiles
© K. Coder 2015
2) How do you determine distance
between points using a map?
To determine distance between two locations on the
map use the map scale.
• Map scale: the part of the map (usually at the
bottom) that gives you distance in miles and/or
kilometers
• If the map scale is in kilometers, the contour lines
are elevations in meters.
• If the map scale is in miles, the contour lines are
elevations in feet.
2) How do you determine distance
between points using a map?
There are two ways of determining distance:
• Straight line distance: determining the
distance of a straight line drawn between
two locations
• Curved line distance: determining the
distance along a curved feature (road,
tracks, trails, rivers)
2) How do you determine distance
between points using a map?
Straight Line Distance:
To determine the distance between
locations on a map, you will need a piece
of scrap paper.
1. Place the scrap paper on the straight
line between the two locations. You may
have to use your imagination sometimes if
the line is not drawn for you!
2. Make a mark on the edge of the scrap
paper at the two locations.
3. Move the scrap paper to the map scale
so that one of the marks is lined up with
zero.
4. The other mark indicates the distance.
2) How do you determine distance
between points using a map?
Example: Determine the straight line distance
between the given points using the map below.
Points
Distance
1) A and B
__________
4 km
2) How do you determine distance
between points using a map?
Example: Determine the straight line distance
between the given points using the map below.
Points
2) B and C
Distance
__________
3.2 km
2) How do you determine distance
between points using a map?
Curved Line Distance:
To determine the distance between locations on a map, you will need
a piece of scrap paper.
1. Place the scrap paper on the straight line nearest your starting
point. Mark the location of your starting point on the edge of the scrap
paper.
2. Make a mark on the edge of the scrap paper where the first
straight line distance ends. Make a mark on the map at this exact
location.
3. Pivot your paper so that it lines up with the next straight line of the
feature. Make a mark where this straight-line distance ends.
4. Continue this until you have reached your ending point.
5. Move the scrap paper to the map scale so that the starting point
mark is lined up with zero
6. The ending point mark indicates the distance of the entire curved
line.
2) How do you determine distance
between points using a map?
2) How do you determine distance
between points using a map?
Example: Determine the
length of the Green River from
Point A to Point F on the map
above.
= 4km + 4km + 2.5km
= 10.5 km
4
0
04
4
2.5 4
© K. Coder 2015
✓ Review – Measuring Distances:
1. Using ESRT page 3 and a piece of scrap
paper, determine the straight-line distance
between the following two cities in both miles
and kilometers. Note: each city is located at the
point near the name of the city.
Cities
Elmira & Binghamton
Syracuse & Oswego
Ithaca & Utica
Kilometers
Miles
✓ Checkpoint – Measuring Distances:
2. A hiker is using the map below to plan his
hike. What is the approximate distance along
the trail between point C and D? Label your
answer with the correct units.
0
3
3) How do we map fields?
• Isolines: a line that connects equal values
in a field
3) How do we map fields?
In Earth Science, we will spend a lot of time looking at three
specific types of field maps:
• Elevation: contour lines connect equal elevations
• Temperature: isotherms connect equal temperatures
• Pressure: isobars connect equal pressures
• Other field maps we will see show snowfall, rainfall, volcanic
ash, earthquake magnitudes, odor fluctuations, pollution
concentrations
Isotherms on a Weather Map
© K. Coder 2015
Isobars on a Weather Map
4) How do we draw and read isolines?
1. All points on any
one isoline have the
same measured
value.
4) How do we draw and read isolines?
2. All of the values
on 1 side of the
isoline are higher
than the values of
the isoline. All values
on the other side of
the isoline are lower
in value than the
isoline.
4) How do we draw and read isolines?
3. All isolines extend
to the edge of a map
unless they make a
complete circle.
4) How do we draw and read isolines?
4. Isolines can never
cross or touch each
other.
4) How do we draw and read isolines?
5. Isolines tend to
have gentle curves
rather than sharp
angles.
✓ Checkpoint – Reading Isolines
Students in a class were told to draw the 22 and 24 value
isoline on the maps provided. Some of the students made
errors. Each map below is incorrect for one reason. Using the
rules of isolines, explain why the map is incorrect.
✓ Review – Drawing Isolines
Using a pencil, draw isolines with an interval of 1.
Work neatly and carefully.
5) How is elevation shown on a map?
• Topographic (contour) map: a map that
shows changes in the elevation of Earth’s
surfaces
© K. Coder 2015
5) How is elevation shown on a map?
o Contour line: an isoline used on a topographic map
to connect locations that have the same elevation
(see lines on the bottom of this page).
Contour line
© K. Coder 2015
5) How is elevation shown on a map?
Figure 1.
3-dimensional landform
from our perspective
2-dimensional topographic
map of this landform
(viewed from above)
▪ All elevations are measured above sea
level, which has a value of zero.
5) How is elevation shown on a map?
Figure 1.
This
landform
must be in
the ocean!
3-dimensional landform
from our perspective
2-dimensional topographic
map of this landform
(viewed from above)
• The contour line that borders the ocean
always has an elevation of zero feet or
meters. (This does not apply to lakes and
ponds.)
5) How is elevation shown on a map?
▪ Contour lines that are in the shape of circles
indicate a hill or mountain peak. (see Figure 1)
Figure 1.
3-dimensional landform
from our perspective
2-dimensional topographic
map of this landform
(viewed from above)
5) How is elevation shown on a map?
o Index lines: isolines that have their value
labeled on them (frequently darker than the
other isolines).
Contour line
Index line
© K. Coder 2015
6) How do you determine values of
contour lines on a topographic map?
• Contour interval: this is the difference in
value between isolines that are next to
each other.
o The contour interval on a map will never
change.
6) How do you determine values of
contour lines on a topographic map?
• Procedure for determining
contour interval of a map:
1. Find the difference in value
between index lines (subtract
smaller # from larger #).
• Example: What is the
contour interval on
the map below?
20 meters
______________
2. Divide difference between
index lines by the number of
spaces between the contour
lines that are between the index
lines.
80
40
80 – 40 meters = 40 meters
40 meters / 2 spaces = 20 meters
Lake
Elevations in meters
✓ Review – Contour Interval:
Use the topographic map below to answer
questions
7) How can you determine possible
elevations between contour lines?
• Possible elevations: locations in between
contour lines can be estimated.
o Elevations can be any value between the
contour values (but cannot be equal to either
of the contour values.
7) How can you determine possible
elevations between contour lines?
o Example: What are the possible elevations,
in feet, of point X on the topographic map
Any value from 21 to 39 feet
below? ___________________________
40
Lake
20
X
8) How are depressions (or ditches) shows on contour
maps?
• Hachured lines ( | | | | | | ): contour lines
that indicate a depression in the ground.
290
290
8) How are depressions (or ditches) shows on contour
maps?
• Rules for reading
hachured lines:
Contour line it is
between
1. The outer most Contour interval = 10
290
hachured line is
equal in elevation to
the lower of the
contour lines it is in
between.
2. The elevation of any
inner hachured line
is equal to a
decrease in
elevation by the
contour interval.
Outer most
hachured line
Next
hachured
line
290
8) How are depressions (or ditches)
shows on contour maps?
• Example: On the map below, what is the
40 meters
elevation of point E? __________
Hachured lines
© K. Coder 2015
✓ Review – Possible Elevations & Hachured Lines:
1. Use the topographic map below to answer
the following questions. Elevations are in feet.
9) How are changes in slope shown on a
topographic map?
• Slope: how quickly the elevation of the
land changes
© K. Coder 2015
9) How are changes in slope shown on a
topographic map?
1. The more closely spaced the contour
lines are, the steeper the slope of the
land.
2. The more widely spaced the contour line
are, the more gentle the slope.
Gentle slope
Steep slope
10) How can the steepness of a slope be
calculated?
• Gradient: how rapidly a “field value”
changes over a particular distance.
• Field values: the value of what you are
measuring that you plot on a map
▪ On a topographic map, the field values are
elevations.
10) How can the steepness of a slope be
calculated?
• Equation for gradient (found on ESRT
front cover)
Use isolines on map
Use map scale
10) How can the steepness of a slope be
calculated?
• Example Problem: Point A and point B are
locations 0.24 mile apart on a ski slope in
northern New York. Point A has an elevation
of 1,560 feet and point B has an elevation of
1,800 feet. What is the gradient between
these points? Show your work.
Gradient = change in field value
distance
= 1800 – 1560 feet
0.24 miles
=
240 feet
0.24 miles
= 1000 feet/mile
✓ Checkpoint – Gradient:
1. Determine the gradient between point B and D on
the map below. Show your work.
11) How can the direction of river flow be
determined using a topographic map?
River Flow Direction:
1. Rivers always flow downhill (from high elevation
to low elevation).
11) How can the direction of river flow be
determined using a topographic map?
River Flow Direction:
2. Rivers always flow towards the ocean.
© K. Coder 2015
11) How can the direction of river flow be
determined using a topographic map?
River Flow Direction:
3. Rivers always flow in the opposite
direction from which contour lines bend
when they cross the river.
Notice how the contour lines bend when they cross the river.
They point “upstream”, meaning the opposite way the river is
flowing.
Mt Marcy
So…. In which
general direction
is this river
flowing?
South/
Southwest!
© K. Coder 2015
11) How can the direction of river flow be
determined using a topographic map?
River Flow Direction:
3. Rivers always flow in the opposite
direction from which contour lines bend
when they cross the river.
Example: Which direction is the
Hammer Stream flowing?
__________________________
Hammer stream flows
southeast
________________________
✓ Review– River Flow:
Base your answers to questions 1 and 2 on the
topographic map below.
__________________________________
12) What do features on a topographic
map look like in real life?
• Profile: shows the side view of an Earth
surface
12) What do features on a topographic
map look like in real life?
• Example: Construct a profile for the
topographic map below.
40
60
80
80
© K. Coder 2015
100
100
0
20
40
20
60
100
0
B
20
40
60
80
100
0
A
40
80
20
40
60
80
100
20
60
0
0
A
40
60
80
20
10
0
0
B
Hilltop
has to
curve
above the
100 m
line, but
does not
hit the 120
line.