chapter 3 up to booking method.pdf
- 1. CHAPTER THREE VERTICAL DISTANCEMEASUREMENT( LEVELING) 1 Content :- Introduction Definitions of Basic Terms Principle of leveling The Leveling Instrument Booking Methods of Leveling and Reduction of Levels Types of Leveling Errors in leveling Engineering application of leveling
- 2. 3.1 Introduction Leveling is a method of surveying used for determination of the difference of elevations or Levels of various points on the surface of the earth. The elevation of a point is its vertical distance above or below a reference level, called datum. The most commonly used datum is the mean sea Level (M.S.L) 2
- 3. Leveling is an important for many engineering works and construction projects. Leveling is needed for the design of highways, railways, and canals e.t.c and for locating the gradient lines. 3
- 4. Definitions of Basic Terms Vertical line: is a line from the surface of the earth to the earth's center. Horizontal line: is a straight line perpendicular to a vertical line. Mean sea level (MSL): The average height of the sea's surface for all stages of the tide over a specified Vertical control: A series of benchmarks or other points of known elevation established throughout an area, Reduced level (RL): The RL of a point is its height above or below a reference datum. 4
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- 6. 3.2 Definitions of Basic Terms 1.Station.The station is the point where the staff is held for taking reading (observation) from a leveling instrument. 2. Bench mark (BM): -is a permanent or semi permanent point of known elevation that provides beginning point for determining the elevation of other points. 3.Height of the instrument. (H.I). It is the elevation of the line of sight with respect to the datum. The elevation of the line of sight of the telescope 6
- 7. 4.Backsight (BS) - It is the reading taken on a staff held at point of known elevation or at the point whose elevation has already been determined. The reading taken after setting the instrument set up(the first reading) 5.Foresight (FS) - The last sight taken before the instrument is moved 7 Definitions of Basic Terms …
- 8. 6.Intermediate sight (IS) - It is the reading taken on a staff held at point whose elevations is required, Any sighting that is not a back sight or fore sight 7. Line of Collimation – Imaginary line that passes through leveling instrument at Cross-Hairs . 8.Turning point. (T.P.) :-For leveling over a long distance, the instrument has to be set up a number of times. • A turning point is the point selected on the route before shifting the instrument. 8 Definitions of Basic Terms …
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- 10. 9. Balancing of sight. To reduce the effect of instrumental and other errors, the distance of the point where a back sight is taken and the distance of the point where a fore sight is taken, as measured from the instrument station, should be approximately equal. 10
- 11. 2.Steps in leveling 1. When the leveling instrument has been properly leveled, the bubble tube axis and the line of sight are horizontal and the vertical axis of the instrument is truly vertical. 2. In practice, the leveling instrument is set up at a convenient position, and the one staff is kept at a point of known elevation. 3. The reading is taken on the staff and the level of the line of sight is determined. 11
- 12. 4. Now the 2nd staff is kept on the point of the unknown elevation and a reading is taken. 5. The level of the point is determined from the level of the line of sight already computed and from the 2nd staff reading. 12
- 13. 2.Principle of direct leveling 13
- 14. The Leveling Instrument The Level dumpy levels, tilting levels, and automatic levels Has a set of cross-hairs Can be turned through 360° horizontally Consist of a high-powered telescope Attached to a spirit or bubble level that keeps the line of sight of the telescope horizontal 14
- 15. The Tripod:- A fully adjustable 3-legged stand on which the level sits. 15
- 16. The Staff A measuring stick, usually 4m tall, and clearly marked in divisions of 10mm. 16
- 17. Reading the E Staff • Each “E” is 50mm • Each Part of the E is 10mm • Millimeters are interpolated • Staff is read to the millimeter 17
- 18. Bubble Keep the staff upright Any tilt will disturb your readings 18
- 19. Methods of booking and reduction of Levels (1)Height of Instrument (HI) method :- The desired elevation of a point is found by:- I. adding BS in to given benchmark to find height of instrument II. subtracting FS from height of instrument Or RL of a point = ( RLBM +BS) – FS) = HI – FS 19
- 20. Computation of Elevations Booking Methods 1.Height of Instrument (HI) method 20
- 21. 1.Height of Instrument (HI) method station BS IS FS HI Elevation Remar k A EleA a b B T.P c C 21 S1 S2 S3 S4 S5 56 S7 H.IA=EleA+S1 Ha=H.IA-S2 Hb=H.IA-S3 HB=H.IA-S4 Hc=H.IB-S7 H.IB=EleB+S5 Hc=H.IB-S6 Σ B.S. Σ F.S. Check: Σ B.S. – Σ F.S. = Last R.L. – First R.L.
- 22. • Let as done the next example 22
- 23. Elevation 100.00 BS 12.64 FS 3.11 Stn BM1 TP1 Elevn/R.L BS FS HI TP1 BM1 12.64 112.64 3.11 109.53 BS 10.88 10.88 120.41 FS 2.56 TP2 2.56 TP2 117.85 BS 9.72 9.72 127.57 BM2 FS 3.10 BM2 3.10 124.47 100.00 23 1. BS + Elevation = HI 2. HI - FS = New Elev 1.Height of Instrument (HI) method
- 24. Change in elevation: summation of the BS and the FS then subtract +33.24 -8.77 Change in elevation = 33.24 -8.77 = 24.47 Point BM1 TP1 Elevation BS FS HI 12.64 112.64 3.11 109.53 10.88 120.41 2.56 TP2 117.85 9.72 127.57 BM2 3.10 124.47 100.00 ΣΔh = BM2Elev – BM1elev = ΣBS – ΣFS 24
- 25. Computation of Elevations Example:-by Using The Following Figure A. Prepare The Field Book B. Fill The Staff Reading C. Calculate The Elevations Of Points TP1 And TP2? BS 1.27 FS 4.91 TP1 BM BS 2.33 FS 6.17 TP2 Elevation 356.68 25
- 26. 2.Rise and Fall Method Rise and fall (RF) method: – If 2nd red reading > first rod reading ⇒ fall If 2nd rod reading < first rod reading ⇒ rise Then RL of 2nd station = RL of first station - fall or RL of first station + rise 26
- 27. Rise and fall method Station B.S I.S F.S (+)Rise (-)Fall Elev Remarak A hA a b B c C 27 S1 S2 S3 S4 S5 S6 r1=S1 – S2 f2 = S3 – S4 f1=s2-s3 f3 = S5 – S6 r2=S6-S7 ha+=hA + r1 hb = ha – f1 hB = hb – f2 hc = hB – f3 hC = hc + r2 (b) For the rise and fall method Check:-Σ B.S. – Σ F.S. = Σ Rise – Σ Fall = Last R.L. – First R.L. S7 Σ B.S. Σ F.S Σ Rise Σ Fall
- 28. RISE AND FALL METHOD Station B.S I.S F.S Rise(+) Fall(-) Elev(R.L Remarke 1 2.390 31.517 BM 2 1.985 3 1.318 4 0.988 1.612 5 1.502 6 1.415 7 2.420 0.316 8 0.532 TBM Σ=5.798 Σ=2.46 0 Σ=4.146 Σ=0.808 28 NOTE:- (+) donates rise and (-) fall
- 29. RISE AND FALL METHOD Station B.S I.S F.S Rise(+) Fall(-) Elev(R.L Remarke 1 2.390 31.517 BM 2 1.985 0.405 31.922 3 1.318 0.667 32.589 4 0.988 1.612 0.294 32.295 5 1.502 0.514 31.781 6 1.415 0.087 31.868 7 2.420 0.316 1.099 32.967 8 0.532 1.888 34.855 TBM Σ=5.798 Σ=2.46 0 Σ=4.146 Σ=0.808 29 NOTE:- (+) donates rise and (-) fall