1. Distance Measurement

2. Three Types of Distances
Vertical
Horizontal
Slope

3. Techniques of Distance Measurement
Pacing
Electronic distance measurement (EDM)
Fiberglass tapes
Steel tapes

4. Techniques of Distance Measurement
Pacing
is a useful method of approximate measure. Another important use for pacing is for a rough check for all key points in construction layouts.
Electronic distance measurement (EDM)
function by sending a light wave along the path to be measured from the instrument station, and then the instrument measures the difference between the transmitted light wave and the light wave as it is refelected back from the prism.

5. Principles of EDM

6. Steel Tape and Plumb bob

7. Steel Tape Graduations
Graduated throughout
Cut tape
Add tape

8. Steel Tape Graduations

9. Taping Steps
1- carries the tape forward , ensuring the tape is free of loops. 2- prepare ground surface for the mark 3- Applies proper tension after ensuring that the tape is straight. 4- place marks (wooden stakes, iron bars) 5- Take and record the measurements of distances

10. Taping Accessories Plumb bob
used to maintain the horizontal alignment.
Hand level
used to keep the steel tape horizontal when measuring.

11. Horizontal Taping Using a Plumb Bob at One End

12. Horizontal Taping Using Plumb Bobs at Both Ends of the Tape

13. Hand Level

14. Taping Correction Slope corrections
Survey distance can be measured either horizontally or on a slope. On the plan survey measurements have to be horizontal distances.
Sag corrections
The error in measurements due to sag can be eliminated by increasing the applied tension.

15. Systematic Taping Errors
Slope can be defined as a gradient or rate of grade. The gradient is expressed as a ratio of the vertical distance over the horizontal distance. This ratio when multiplied by 100 will give a percentage gradient.
Erroneous length
Temperature
Tension and Sag

16. Random Taping errors Slope (Estimating Horizontal) Temperature
Tension and sag
Alignment
Marking and Plumbing

17. Mistakes Taping Measuring from wrong marker
Reading the tape incorrectly or transporting figures
Recording the value incorrectly in the notes.
Making arithmetic mistakes in some of dimensions and error mistakes. how to avoid this mistake?

18. Example 1:
A road centerline gradient falls from station0+00 with an elevation of m to station 1+50 at rate -2.5% . What is the elevation at station 1+50?

19. Example 2:
A road run from a station 1+00 with an elevation of m to station m with an elevation of m. What is the slope of grade line?

20. Example 3:
A measurements was recorded as m with a 30m- tape that was only m under standard conditions. What is the corrected measurements?

21. Tension and Sag Correction
This tape is made with a metallic alloy known as invar, an alloy of nickel and steel that possesses a very low coefficient of expansion when submitted to thermal variations. This expansion invariance was essential in making accurate measurements

22. Tension and Sag Correction

23. Tension and Sag Correction
Unit
Description
Metric (SI) CP
Correction due to tension per tape length m Cs
Sag correction per tape length L
Length of tape under consideration Ps
Standard tension N
Typical standard tension
50 N P
Applied tension A
Cross sectional area m2 E
Average modulus of elasticity of steel tapes
20x1010 N/m2
Average modulus of elasticity of Invar tapes
14.5x1010 N/m2 w
Weight of tape per unit length
N/m W
Weight of tape

24. Example 4:
A 30-m tape is used with a 100-N force, instead of the standard tension of 50N. If the cross-sectional area of the tape is 0.02 cm2, what is the tension error per tape length?

25. Exercise
1) It is required to layout a rectangular building 250 m wide and 345 m long. If the steel tape use is m (Under standard condition) what distance should be laid out?

26. 2) A distance of 177. 50 m was measured along 3% slope
2) A distance of m was measured along 3% slope. Compute the horizontal distance

27. 3) A 30 m steel tape known to be 30
3) A 30 m steel tape known to be m (under standard conditions) was used to record a measurement of m. What is the corrected distance?

28. 4) The slope distance between two points 29
4) The slope distance between two points m and the difference in elevation between the points is m. compute the horizontal distance.