Date post: | 18-Dec-2015 |
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What is a topographic map?
• A topographic map is a map that shows changes and shape in the elevation of land.
Contour lines• A line on a map representing a
corresponding imaginary line on the ground that has the same elevation along its entire length.
Contour Interval
• Difference in elevation of succeeding contour lines; determined by relief.
• Contour interval can be calculated by finding the difference in elevation between 2 contour lines.
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Contour Interval• Difference in elevation of succeeding contour lines,
determined by relief—the difference in elevation between any 2 points.
• The contour interval will be given at the bottom of the map.
Rules for Contour Lines2. Contour lines bend upstream or cross a valley (points in
direction opposite to the flow of the stream) are called “V”-Shaped. – If the stream flows through the valley the “V” will point
upstream, or within the direction opposite to the flow of the stream.
“V” Points• When you walk straight across a stream, you walk downhill
to the stream, and uphill away from the stream.
• In order to cross a stream and stay at the same elevation, you would have to walk upstream to cross over.
Rules for Contour Lines
3. A contour line of one elevation never crosses or divides a contour line of another elevation.– Each contour line is one elevation!!
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Rules for Contour Lines4. Contour lines form closed loops around hilltops.
Depressions are encircled by contour lines with hachure marks. (short lines within the depression that point toward lower elevations.)
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Hilltops
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Depressions
Hill or Depression???
To decide if you are looking at a hill or a depression,a. Read the elevation numbersb. Look for hachures
1. Short lines drawn inside a depression2. They point toward lower elevations
Rules for Contour Lines
5. Contours are widely spaced on gentle slopes and closely spaced on steep slopes. – Lines close together = STEEP SLOPE– Lines far apart = GENTLE SLOPE
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Gentle Slope
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Steep Slope