1. Levelling – Height Measurement
BE1S204
David Harper

2. Introduction to today’s lecture
Benchmarks
Height Plane Collimation (HPC) Levelling
Rise and Fall Levelling
Worked examples

3. Bench marks
Published height

4. Bench marks (cont.)
Published height

5. Principles of Levelling

6. Principles of Levelling (cont.)
Bench Mark (known Datum)

7. Principles of Levelling (cont.)

8. Principles of Levelling (cont.)

9. Principles of Levelling – Staff readings
A typical section through a staff – Note, first 1 m is black numbering, second 1 m is red, third 1 m is black etc. Staff is graduated every 1 cm, you must estimate the millimetre readings. UK staves have 0 m reading at the bottom whereas European staves have 0m at the top. Bar-coded staves are used with electronic digital instruments only.

10. Principles of Levelling – Staff readings (cont.)

11. Principles of Levelling – Staff readings (cont.)

12. Principles of Levelling – Staff readings’ answers (cont.)

13. Principles of Levelling – Booking Rules
Start and finish on “known” point. Usually TBM or OSBM or OBM.
TBM = Site Datum (Temporary Bench Mark)
OSBM = Ordnance Survey Bench Mark
OBM = Ordnance Bench Mark
Back sight = 1st Staff Reading.
Foresight = Last Staff Reading.
Intermediate = All other staff readings.

14. Principles of Levelling – Calculation Rules
Backsight + Reduced Level = HPC (Height Plane Collimation).
HPC – Intermediate Level = Reduced Level
HPC – Foresight = Reduced Level
Check
Sum of Backsights st Reduced Level
Difference
Sum of Foresights Last Reduced Level

15. Levelling – Methods of Booking – Height of Collimation
(2.085)

16. Levelling – Methods of Booking – Height of Collimation (cont.)

17. Levelling – Methods of Booking – Rise and Fall

18. Levelling – Methods of Booking – Rise and Fall (cont.)

19. Levelling – Change Points (CP)
Why do we use Change Points?
3 main reasons:
Obstructions – there is an obstruction preventing surveyor viewing staff with level, therefore necessary to implement a CP.
Gradients / height difference in ground preventing efficient use of equipment.
Distance (maximum for accuracy 80 – 100 m).

20. Levelling Equipment and Lasers (cont.)

21. Levelling Equipment and Lasers – Tribrach Mounted Level

22. Levelling Equipment and Lasers – Tribrach Mounted Level (cont.)

23. Levelling Equipment and Lasers – Tribrach Mounted Level (cont.)

24. Levelling Equipment and Lasers – Tribrach Mounted Level (cont.)

25. Levelling Equipment and Lasers

26. Levelling Equipment and Lasers

27. Levelling Equipment and Lasers

28. Levelling Equipment and Lasers

29. Levelling Equipment and Lasers

30. Levelling Equipment and Lasers
Carrying Handle – makes it easy to carry this lightweight (15 lbs) laser. Self levelling means no pre-levelling
Laser Beam – it only turns on when the laser is level, thus avoids mistakes
Early Warning System – shuts off laser beam if laser is knocked off level. Turns it back on only when laser has automatically re-levelled itself.
Laser Window – ensure that the laser is completely sealed and waterproof because of this precision optical glass
Rotor Control – lets you point laser beam at a target for rapid height adjustment during set up. Controls spinning speed of laser beam.
Electrical Connections –completely waterproof & operate all day on a lightweight battery. Yellow pilot light shows when power is on & warns when battery is low.
Self Levelling Controls – green light lets you know laser has self levelled itself.
Vertical Accessory Bullseye Level – use if for rough adjustment when setting up for line or plumb. Laser self plumbs electronically.
Housing- rugged castings and extrusions protect self levelling system by enclosing it completely to ensure tough reliability.
Base - has 3 legs for fast set up on any solid surface. Mounting ring lets you mount laser on any standard tripod.

31. Levelling Equipment and Lasers – Cowley and Water Levels

32. Levelling Equipment and Lasers – Cowley and Water Levels (cont.)

33. Levelling Equipment and Lasers – Cowley and Water Levels (cont.)

34. Water Level

35. Levelling Equipment and Lasers – Cowley and Water Levels (cont.)

36. Levelling Equipment and Lasers – Checking the Level

37. Levelling Equipment and Lasers – expected accuracy

38. Levelling: Mistakes and Checks

39. Points to remember when levelling
move

40. Height Plane Collimation (HPC) Levelling exercise

41. HPC Levelling Exercise – No. 2

42. HPC Levelling Exercise – No. 3

43. Rise & Fall Levelling Exercise – No. 1

44. Rise & Fall Levelling Exercise – No. 2

45. Rise & Fall Levelling Exercise – No. 3

46. Summary of today’s lecture
Benchmarks
Height Plane Collimation (HPC) Levelling
Rise and Fall Levelling
Worked examples