NOTES Topographic Maps 2 - NYS Earth Science · topographic map? 1. The more closely spaced the contour lines are, the steeper the slope of the land. 2. The more widely spaced the

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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

Guided Notes Topographic Maps

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.


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)


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 Distance

2) B and C __________3.2 km


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.

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Example: Determine the length of the Green River from Point A to Point F on the map above.

= 10.5 km

0 40 4 44 4 2.5

= 4km + 4km + 2.5km

✓ 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 Kilometers Miles

Elmira & Binghamton

Syracuse & Oswego

Ithaca & Utica

✓ 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 33

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

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Isotherms on a Weather Map

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.


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.


3. All isolines extend to the edge of a map unless they make a complete circle.


4. Isolines can never cross or touch each other.


5. Isolines tend to have gentle curves rather than sharp angles.

✓ Checkpoint – Reading IsolinesStudents 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 IsolinesUsing a pencil, draw isolines with an interval of 1. Work neatly and carefully.

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5) How is elevation shown on a map?

• Topographic (contour) map: a map that shows changes in the elevation of Earth’s surfaces

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Contour line

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).


▪All elevations are measured above sea level, which has a value of zero.

Figure 1. 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.)



This landform

must be in the ocean!


▪ Contour lines that are in the shape of circles indicate a hill or mountain peak. (see Figure 1)



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o Index lines: isolines that have their value labeled on them (frequently darker than the other isolines).

Contour line

Index line

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 #). 2. Divide difference between index lines by the number of spaces between the contour lines that are between the index lines.

• Example: What is the contour interval on the map below? ______________

80

Lake40

20 meters

80 – 40 meters = 40 meters

40 meters / 2 spaces = 20 metersElevations 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 below? ___________________________ Any value from 21 to 39 feet

Lake20

40X

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:

1. The outer most

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.

290

290

Outer most hachured line

Contour line it is between

Next hachured

lineContour interval = 10

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8) How are depressions (or ditches) shows on contour maps?

• Example: On the map below, what is the elevation of point E? __________ 40 meters

Hachured lines

✓ Review – Possible Elevations & Hachured Lines:  

1. Use the topographic map below to answer the following questions. Elevations are in feet.

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9) How are changes in slope shown on a topographic map?

• Slope: how quickly the elevation of the land changes

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.


• Equation for gradient (found on ESRT front cover)

Use isolines on map

Use map scale


• 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).



3. Rivers always flow in the opposite direction from which contour lines bend when they cross the river.

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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!

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.

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604020 80 80 60 40 20 01001000

0 A

20 40 60 80 100 10080 60 40 20 0

B

0 A

20 40 60 80 100 10080 60 40 20 0

B

Hilltop has to curve above the 100 m line, but does not hit the 120 line.

Documents

NOTES Topographic Maps 2 - NYS Earth Science · topographic map? 1. The more closely spaced the contour lines are, the steeper the slope of the land. 2. The more widely spaced the