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Objectives: -Explain how topographic maps use contour lines to show elevation PowerPoint PPT Presentation


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Chapter 3 Section 3 Topographic Maps (note to teacher: have topographic map ready and don’t close it until lecture is over). Objectives: -Explain how topographic maps use contour lines to show elevation -Describe topographic map symbols

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Objectives: -Explain how topographic maps use contour lines to show elevation

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Objectives explain how topographic maps use contour lines to show elevation

Chapter 3 Section 3Topographic Maps (note to teacher: have topographic map ready and don’t close it until lecture is over)

Objectives:

-Explain how topographic maps use contour lines to show elevation

-Describe topographic map symbols

-Demonstrate how to use topographic maps to determine the shape of the land, the flow of rivers, and distance


Topography

Topography -

  • The natural and human-made surface features of an area.


Topographic maps

Topographic Maps

  • Common type is the 7.5 minute map commonly called a quadrangle, that spans 7.5 minutes of latitude and 7.5 minutes of longitude

  • Topographic Map of Sedona


7 5 minute map

7.5 Minute Map

  • Has a scale of 1:24,000

    • (one inch represents 2,000 ft.)


Topographic maps con t

Topographic Maps Con’t

  • Contour lines – narrow brown lines that indicate elevation

  • Topo

  • Contour Interval – The difference in elevation between consecutive contour lines.

  • contour interval 40


Calculating contour interval

Calculating Contour Interval

  • Subtract 2 adjacent bold contour lines and divide by the number of lines

  • 200-100=100

  • 5 contour lines

  • 100/5=20

  • C.I. = 20 ft


Slope

Slope

  • The distance between one contour line and the next indicates steepness.

  • Contour lines that are close together = steep

  • Contour lines with space between them = gradual

  • Rise/Run = average slope


Green represents vegetation blue represents water

Green represents vegetation Blue represents water


Bench marks

Bench Marks

  • The exact location where elevation is known and noted on a brass or aluminum plate which is permanently set into the ground

  • On a map it is noted with “BM” next to a X with the elevation given.

  • benchmark


Army corps of engineers bench marks

Army Corps of Engineers Bench Marks


Usgs bench mark

USGS Bench Mark


Geodetic bench mark

Geodetic Bench Mark


Spot elevations

Spot Elevations

  • Elevations of road forks, hilltops, lake surfaces, and other points of interest.

  • Marked with small crosses “+”

  • spot elevations


Understanding symbols

Understanding Symbols

  • Contour lines that form circles indicate hills or mountains

  • Depression contours indicate a depression in the landscape


Other features

Other features

  • Contour lines that cross a river from an arrow which points toward the source

  • Human made features are depicted in black

  • Thickly settled regions are pink


Magnetic declination

Magnetic Declination

  • The angle by which a compass needle will vary from true north


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