1. Linear Measurement
NG1H703 & BE1S204
David Harper

2. Introduction to today’s lecture
Linear measurement – equipment
Calculations – triangles
Slope Correction
Overcoming obstacles to linear measurement
Worked examples

3. Linear measurement - equipment
Steel tape measure -30 metres -complete with tension handle.
Note – the tension handle applies a constant tension to the tape and thus virtually eliminates any error due to the tape being allowed to sag.

4. Linear measurement – equipment (cont.)
Ranging Rods – brightly coloured rods approx. 2.0 m long used for the establishment of straight lines, especially when the distance to be measured exceed the length of the tape.

5. Linear measurement – equipment (cont.)
Station or Reference Pegs – usually softwood 50mm square and at least 500mm long.

6. Linear measurement – equipment (cont.)
0/60

7. Linear measurement – equipment (cont.)
Sundries:
Claw hammer
Nails
Pocket spirit level
Chalk
String line
Bag- large enough to hold all items except ranging rods and station pegs
Stands for supporting ranging rods on firm ground

8. Calculations - triangles

9. Calculations – triangles (cont.)

10. Calculations – triangles (cont.)

11. Calculations – triangles (cont.)

12. Calculations – triangles (cont.)

13. Calculations – triangles (cont.)

14. Calculations – triangles (cont.) – Pythagoras’ Theorem

15. Calculations – triangles (cont.) – Pythagoras’ Theorem

16. Calculations – triangles (cont.) – Pythagoras’ Theorem

17. Calculations – triangles (cont.) – Pythagoras’ Theorem

18. Calculations – triangles (cont.) – Pythagoras’ Theorem

19. Calculations – triangles (cont.) – Pythagoras & Isosceles triangle
If the base AC is bisected at B, then lines AB = BC and the line extended through D then the angle DBC = DBA = 900

20. Calculations – triangles (cont.) – Equilateral triangles

21. Calculations – triangles (cont.)X
N.B. The acronym S.O.H.C.A.H.T.O.A.

22. Calculations – triangles (cont.) – Similar triangles

23. Calculations – triangles (cont.) – Slope Correction
or d² = s² - h²

24. Calculations – Slope Correction (Cont.)d C h

25. Calculations – Slope Correction (cont.) – Step Chaining

26. Calculations – Slope Correction (cont.) – Step Chaining (cont.)

27. Overcoming obstacles to linear measurement

28. Overcoming obstacles to linear measurement

29. Overcoming an obstacle which obstructs measurement

30. Overcoming an obstacle which obstructs measurement (cont.)

31. Overcoming an obstacle which obstructs measurement (cont.)

32. Overcoming an obstacle which obstructs measurement (cont.)X

33. Overcoming an obstacle which cannot be measured around

34. Overcoming an obstacle which cannot be measured around (cont.)
=XD1

35. Measurement: Mistakes and Checks

36. Measurement: Mistakes and Checks (cont.)if

37. Worked examples – Measurement of a straight line

38. Worked examples – Measurement of a straight line (cont.)

39. Worked examples – Measurement around an obstacle

40. Worked examples – Measurement around an obstacle (cont.)

41. Worked examples – Measurement around an obstacle (cont.)

42. Worked examples – Measurement around an obstacle (cont.)

43. Summary of today’s lecture
Linear measurement – equipment
Calculations – triangles
Slope Correction
Overcoming obstacles to linear measurement
Worked examples