C ONTOURS

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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.

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Presentation Transcript
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1

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

240

252

276

263

297

279

280

300

317

320

285

325

314

289

309

298

280

254

281

264

238

240

240

252

276

260

260

263

280

297

300

279

280

.300

317

320

285

325

314

320

289

309

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298

280

280

280

254

281

260

264

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
On to the peak!

300m

200m

100m

Any ideas?

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

300m

200m

100m

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

Think you know our elevation now?

More than 300meters

But less than 350meters

• More than 350 meters, less than 400 meters
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

Uniform Gentle Slope

320

280

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260

300

220

Uniform Steep Slope

320

260

300

240

220

200

180

280

160

140

Concave Slope

240

220

320

260

280

300

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
320

300

280

260

CONICAL HILL

320

300

280

260

ASYMMETRICAL HILL

320

300

280

260

CIRCULAR PLATEAU

260

320

280

300

RIDGE

260

320

280

320

300

240

220

300

260

200

280

340

280

260

240

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220

200

300

180

V SHAPED VALLEY

340

280

260

240

320

220

300

200

WATERFALL

CONTOURS: 45 D/7

9293: Ridge

9289: Ridge (uniform)

9390: Ridge (steep)

9489: Hill

7975: Conical hill

9284: Conical hill

9782: Escarpment