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# C ONTOURS PowerPoint PPT Presentation

10. 9. 8. 7. 6. 5. 4. 3. 2. 1. C ONTOURS. What are contours?. Imaginary lines Drawn on a map Connecting places Which are at equal elevation (height above sea level). How are contours drawn?. S. U. R. T. Q. E. P. G. D. F. B. M. A. C. L. I. J. H. O. K. N. 238.

C ONTOURS

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CONTOURS

What are contours?

• Imaginary lines

• Drawn on a map

• Connecting places

• Which are at equal elevation (height above sea level)

How are contours drawn?

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### Contour Interval

• The difference of elevation between two successive contours

• Contour interval on the toposheet is 20 meters.

INDEX CONTOURS

Every 5th contour, with height mentioned

Characteristics of Contours

• All places on the contour line lie at the same elevation

• Contours never intersect each other

• Contour interval (difference between two successive contour values) is uniform throughout the map

• All contour values are multiples of the contour interval

• Height of any place on map can be determined

Spacing between contours

• Widely spaced contours

• Gentle slope

• Closely packed contours

• Steep slope

• Overlapping contours

• Vertical slope

100m

100m

200m

100m

200m

100m

300m

200m

100m

300m

200m

100m

300m

200m

100m

### Any ideas?

Let’sadd contour lines for every 50 meters and see if that helps.

300m

200m

100m

We know that we are above 350m, but less than 400m.

350m

300m

250m

200m

150m

100m

50m

Let’s head down the hill, it’s getting late!

350m

300m

250m

200m

150m

100m

50m

Now what’s our elevation?

If you said somewhere between 200m and 250m you are right!

350m

300m

250m

200m

150m

100m

50m

Let’s try this again!

350m

300m

250m

200m

150m

100m

50m

What’s our elevation now?

If you said 50m or just under, you’re right!

350m

300m

250m

200m

150m

100m

50m

### Let’s now look at the same hill, but the way we might see it from an airplane!

Each color change represents a 50 meter increase.

Now, let’s try the same hike! Our elevation is 0 meters.

Now what is our elevation?

If you said more than 150 meters, but less than 200 meters your right!

Let’s go a little higher.

Think you know our elevation now?

More than 300meters

But less than 350meters

### If we were standing on the peak, what would be our elevation?

• More than 350 meters, less than 400 meters

Let’s head down hill.

Know our elevation?

More than 100 meters,

less than 150 meters

FORM LINES

Drawn where it is not possible to draw contours and there is a prominent relief feature which is lesser in height than the contour interval

### Types of slopes

Uniform Gentle Slope

Uniform Gentle Slope

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220

Uniform Steep Slope

Uniform Steep Slope

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Concave Slope

Concave Slope

240

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300

Convex Slope

Convex Slope

Features of Contour Diagrams

• Spacing gives idea of slope

• Shape of contours resembles shape of relief feature in ariel view

• It is possible to visualise the shape of the relief feature

VISUALISATION

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CONICAL HILL

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260

ASYMMETRICAL HILL

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260

CIRCULAR PLATEAU

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RIDGE

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V SHAPED VALLEY

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WATERFALL

### An Escarpment

CONTOURS: 45 D/7

9293: Ridge

9289: Ridge (uniform)

9390: Ridge (steep)

9489: Hill

7975: Conical hill

9284: Conical hill

9782: Escarpment