topographic maps. a topographic map of part of ithaca

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  • Slide 1
  • Topographic Maps
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  • A topographic map of part of Ithaca
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  • Topographic Maps Maps of an elevation field Show elevation by contour lines Also show other natural and man-made features by using symbols
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  • 1. Contour lines lines the connect points of equal elevation
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  • Contour Lines close together Contour Lines far apart Steep slope Gentle slope
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  • 2. Contour Interval The contour interval on this map is 20? What do you think is a contour interval?
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  • Contour Interval Change in elevation in between two consecutive contour lines Usually listed in key or legend
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  • If you are at sea level, your elevation is 0. The contour line for the coastline is 0.
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  • 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?
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  • Index Contour Lines Every 4 th or 5 th line that is thicker or bolder Line is labeled with the elevation Helps to read the map
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  • Index contour lines are placed every 50 units on this map
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  • What is the spacing of Index Contours on this map? What is the contour interval?
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  • 4. Hills How is a hill depicted on a topographic map?
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  • Hills Closed contours in a circle or elliptical (oval) shape Bulls eye
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  • 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
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  • 5. Hachured Lines Does the elevation go up or down when you see the hachured lines? The first depression line is going to the ________ elevation as the closest contour line down same
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  • 6. Benchmark - EXACT Elevation Indicated by a BM or X on a topographic map
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  • What is the exact elevation of the benchmark on this map? 2919 feet
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  • 7. Streams always flow Downhill from higher elevation to lower elevation Can a stream flow northward? Yes
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  • What direction is this stream flowing? South N
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  • Describe what the contour lines look like when they are crossing a stream? Contour lines point in the opposite direction the stream is flowing! N
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  • Streams always flow in the opposite direction the V or U is pointing.
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  • 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
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  • 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
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  • 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
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  • Map Scales The relationship between distance as measured on a map and the actual distance on Earths surface
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  • Types of Map Scales a.Verbal Scale 1 inch = 20 miles b.Bar Scale One Mile
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  • 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
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  • Maps often give you more than one way to measure distance Represents one mile on the map Represents parts of one mile, ex: one tenth of a mile One kilometer
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