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

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

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### 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 -

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

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

- Has a scale of 1:24,000
- (one inch represents 2,000 ft.)

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

- 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

- 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

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

Spot Elevations

- Elevations of road forks, hilltops, lake surfaces, and other points of interest.
- Marked with small crosses “+”
- spot elevations

Understanding Symbols

- Contour lines that form circles indicate hills or mountains
- Depression contours indicate a depression in the landscape

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

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

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