1 / 28

Distance Measurement

Distance Measurement. Three Types of Distances. Vertical Horizontal Slope. Techniques of Distance Measurement. Pacing Electronic distance measurement (EDM) Fiberglass tapes Steel tapes. Techniques of Distance Measurement. Pacing

rdubose
Download Presentation

Distance Measurement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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 564.22 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 471.37m to station 4+37.25m with an elevation of 476.77m. What is the slope of grade line?

  20. Example 3: A measurements was recorded as 171.278 m with a 30m-tape that was only 29.996 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

  24. Example 4: A 30-m tape is used with a 100-N force, insteda 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. Homework 1 1) It is required to layout a rectangular building 250 m wide and 345 m long. If the steel tape use is 100.02 m (Under standard condition) what distance should be laid out?

  26. Homework 1 2) A distance of 177.50 m was measured along 3% slope. Compute the horizontal distance

  27. Homework 1 3) A 30 m steel tape known to be 30.004 m (under standard conditions) was used to record a measurement of 202.020 m. What is the corrected distance?

  28. Homework 1 4) The slope distance between two points 29.705 m and the difference in elevation between the points is 3.658 m. compute the horizontal distance.

More Related