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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. - PowerPoint PPT Presentation
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CONTOURSCONTOURS
What are contours?
• Imaginary lines• Drawn on a map• Connecting places• Which are at equal elevation (height above
sea level) How are contours drawn?
How are contours drawn?
A
J
E
F D
C
B
T
P
H
L
S
O
R
N
Q
I
M
K
G
U
325
298
297
317 300
314
320
276
279
280
289
238
254
252
264
263
309
285
281
280
240
325
298
297
317 .300
314
320
276
279
280
289
238
254
252
264
263
309
285
281
280
240
320
240
260
280
300
280
280
260
260
300
Contour IntervalContour Interval
• The difference of elevation between two successive contours
• Contour interval on the toposheet is 20 meters.
INDEX CONTOURSEvery 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
Let’s take a walk up a hill!
We’re now at an elevation of 100 meters.
100m
Let’s keep going!
100m
Now we’re at 200m.
100m
200m
Shall we march on?
100m
200m
We’ve made it to 300m!
100m
200m
300m
On to the peak!
100m
200m
300m
We’re on the peak, but what’s our elevation?
100m
200m
300m
Any ideas?
100m
200m
300m
Let’s add contour lines for every 50 meters and see if that helps.
100m
200m
300m
We know that we are above 350m, but less than 400m.
50m
150m
250m
350m
100m
200m
300m
Let’s head down the hill, it’s getting late!
50m
150m
250m
350m
100m
200m
300m
Now what’s our elevation?
50m
150m
250m
350m
If you said somewhere between 200m and 250m you are right!
100m
200m
300m
Let’s try this again!
50m
150m
250m
350m
100m
200m
300m
What’s our elevation now?
50m
150m
250m
350m
If you said 50m or just under, you’re right!
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
320 300
280
260
240 220
Uniform Steep Slope
Uniform Steep Slope
320300280
260240220
200
180
160
140
Concave Slope
Concave Slope
320 300280
260240 220
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
CONICAL HILL
320
300
280
260
ASYMMETRICAL HILL
320300
280
260
CIRCULAR PLATEAU
320300280
260
RIDGE
320300
280 260
SADDLE
320300
280 260320
V SHAPED VALLEY
320
340
300
280260
240
220200
180
WATERFALL
320
340
300
280260
240
220
200
An Escarpment
CONTOURS: 45 D/7 9293: Ridge9289: Ridge (uniform)9390: Ridge (steep)9489: Hill7975: Conical hill9284: Conical hill9782: Escarpment9689: Saddle/ col9783: Col/ Saddle
45 D/101907: Cliff( very steep)2012: V shaped valley