C ONTOURS

1. 10 9 8 7 6 5 4 3 2 1

2. CONTOURS

3. What are contours? • Imaginary lines • Drawn on a map • Connecting places • Which are at equal elevation (height above sea level) How are contours drawn?

4. S U R T Q E P G D F B M A C L I J H O K N

5. 238 240 252 276 263 297 279 280 300 317 320 285 325 314 289 309 298 280 254 281 264

6. 238 240 240 252 276 260 260 263 280 297 300 279 280 .300 317 320 285 325 314 320 289 309 300 298 280 280 280 254 281 260 264

7. Contour Interval • The difference of elevation between two successive contours • Contour interval on the toposheet is 20 meters.

8. INDEX CONTOURS Every 5th contour, with height mentioned

9. 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

10. Spacing between contours • Widely spaced contours • Gentle slope • Closely packed contours • Steep slope • Overlapping contours • Vertical slope

12. Let’s take a walk up a hill!

13. We’re now at an elevation of 100 meters. 100m

14. Let’s keep going! 100m

15. Now we’re at 200m. 200m 100m

16. Shall we march on? 200m 100m

17. We’ve made it to 300m! 300m 200m 100m

18. On to the peak! 300m 200m 100m

19. We’re on the peak, but what’s our elevation? 300m 200m 100m

20. Any ideas? Let’sadd contour lines for every 50 meters and see if that helps. 300m 200m 100m

21. We know that we are above 350m, but less than 400m. 350m 300m 250m 200m 150m 100m 50m

22. Let’s head down the hill, it’s getting late! 350m 300m 250m 200m 150m 100m 50m

23. Now what’s our elevation? If you said somewhere between 200m and 250m you are right! 350m 300m 250m 200m 150m 100m 50m

24. Let’s try this again! 350m 300m 250m 200m 150m 100m 50m

25. What’s our elevation now? If you said 50m or just under, you’re right! 350m 300m 250m 200m 150m 100m 50m

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

27. Each color change represents a 50 meter increase.

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

29. Now what is our elevation?

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

31. Let’s go a little higher.

32. Think you know our elevation now? More than 300meters But less than 350meters

33. If we were standing on the peak, what would be our elevation? • More than 350 meters, less than 400 meters

34. Let’s head down hill.

35. Know our elevation?

36. More than 100 meters, less than 150 meters

39. 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

40. Types of slopes

41. Uniform Gentle Slope

42. Uniform Gentle Slope 320 280 240 260 300 220

43. Uniform Steep Slope

44. Uniform Steep Slope 320 260 300 240 220 200 180 280 160 140

45. Concave Slope

46. Concave Slope 240 220 320 260 280 300

47. Convex Slope

48. Convex Slope

49. 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

50. VISUALISATION