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## PowerPoint Slideshow about ' Topographic Maps' - zaide

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### Rules of Topographic Mapping!!

What are topographic maps?

- A topographic map is a flat map that can be used to show elevation.
- People use different kinds of maps to find out different kinds of information.

Curved loops called contour lines

- A mountain, for example, on a topographic map is drawn as a series of curved loops, one loop inside the other.
- Each loop is called a contour line.
- And each contour line passes throughareas of equal elevation.

- In Figure 1 a mountain is drawn as it might appear on a topographic map. Notice that the first curved line has a number 50, which in this case means an elevation of 50meters.

- The intervals between each contour line on the contour map in Figure 1 are 5 meters.So each line represents an elevation of 5 meters above the line just outside of it.
- In this case, there are 3more contour lines inside the 50 meter line. So the elevation of the peak of this mountain is 0ver 65 meters.

60

55

- Sometimes the contour lines have smallerlines extending inward. In Figure 2, these lines indicate that the elevation is decreasing, notincreasing. The second example in Figure 2, then, shows an area that has an elevation at its center of 35 meters.

40

45

Rules of Topographic Mapping!!

- A contour line connects the points of equal elevation.
- Counter lines that are close together represent steepslopes; those that are far apart represent gentleslopes.

gentle slopes

Steep slopes

Rules of Topographic Mapping!!

- Contour lines NEVER cross or join contour lines of different elevations.
- Closed contour lines represent hills.
- Contour lines form V’s when they crossstreams. The V’s always point upstream.

Rules of Topographic Mapping!!

- Hachures on contour lines indicate the elevation is decreasing. This is called a depression.
- The elevation at the first hachured contour line is the same as the adjacent, lower regular contour line.

- A topographic map shows the height or elevation of land areas. Look at picture 1. This is a mountainous island. Imagine that someone has painted lines on the mountains, and that each line is 500 feet higher than the line before.

Let’s look further

- The lines are called contour lines. They show the shape of the island. The contour lines above would make the topographic map shown here.
- The distance between the contour lines is known as the contour interval.
- The contour interval of this map is 500 feet. Notice that there are two peaks of the mountain.
- On the right side, the lines are closer together, indicating that the right side of the mountain as a steep slope.

Steep slope

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