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TACHYMETRY

TACHYMETRY. LESSON 2 The stadia system Incline Sights With the Staff Vertical. Contents. 1. PRINCIPLES. 2. CALCULATION. 3. PRACTICAL 2. 4. WORK PROCEDURE. Principles. Incline Sight With The Staff Vertical. dH. h i. s = the staff intercept AB

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TACHYMETRY

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  1. TACHYMETRY LESSON 2 The stadia system Incline Sights With the Staff Vertical

  2. Contents 1 PRINCIPLES 2 CALCULATION 3 PRACTICAL 2 4 WORK PROCEDURE

  3. Principles Incline Sight With The Staff Vertical dH hi s = the staff intercept AB h = the length of the centre hair reading from the staff base V = the vertical component XY, the height of the centre hair reading above (or below) the instrument axis D = the length of the line of sight IX H = the horizontal distance required. hi = instrument height

  4. Publication formula To obtain Slope distance; So, D = Ks + C = K(A’B’) + C But, A’B = ABCos atau sCos  So D = KABCos  + C D = Ks.Cos  + C To obtain Horizontal Distanceand Vertical Distance; H = DCos  = Ks.Cos2 + C.Cos  V = Dsin = Ks.Cos.Sin  + C.Sin = ½ (Ks.Sin 2) + C.Sin  DeterminationFirstReducedLevelStation; RLstn= RLTBM – hi V – h DeterminationDifferenceHeight; dH = hi  V – h The reduced level of the instrument position I plus the difference in height equal the reduced level of the staff position S. Therefore: R.L.s = R.L.I + hi ± V – h

  5. Cycle Diagram Where D = Distance K & C = constant (if not given assume K = 100 & C = 0) S = staff intercept H = horizontal distance V = vertical distance  = zenith angle (positive for angles of the elevation, negative for angles of the depression) hi = the height of instrument (always positive) h = the centre hair reading (always negative)

  6. Work procedure - EXAMPLE RESULT PRACTICAL 2 - TACHEOMETRY BOOKING FORM (The stadia system Incline Sights With The Staff Vertical) Text Text Text Text Text

  7. GIVEN THE TBM (Temporary bench mark) – Stn A & B • READING VERTICAL ANGLE BELONG THE SITUATION • TRAVERSE METHOD • TAKE TOPOGRAPHY ITEMS (Tree, Building) Refer the plan AB H = V = S upper= S middle= S lower = BA H = V = S upper= S middle= S lower = B E ED H = V = S upper= S middle= S lower = DE H = V = S upper= S middle= S lower = BE H = V = S upper= S middle= S lower = EB H = V = S upper= S middle= S lower = A D AC H = V = S upper= S middle= S lower = CA H = V = S upper= S middle= S lower = CD H = V = S upper= S middle= S lower = DC H = V = S upper= S middle= S lower = C

  8. Practical 2 E Tree 2 H = V = S upper= S middle= S lower = D Tree 1 H = V = S upper= S middle= S lower = B E A Building 1 H = V = S upper= S middle= S lower = A Building 2 H = V = S upper= S middle= S lower = A D C Tree 3 H = V = S upper= S middle= S lower = C Building 3 H = V = S upper= S middle= S lower = C Building 4 H = V = S upper= S middle= S lower = C b2 b4 b1 b3

  9. Calculation – example for field book

  10. Diagram TRAVERSE READING TOPOGRAPHY READING CORRECTION

  11. EXAMPLE CALCULATION H = Ks.Cos2 + C.Cos  = 100 (2.025 -1.000) . (Cos+80)2 + (0.Cos +80) = 100 (2.025 -1.000) . (Cos+80)2 + 0 = V=½ (Ks.Sin 2) + C.Sin  = (½ (100 .(2.025 -1.000) .Sin (2 . +80)) + (0.Sin +80) = (½ (100 .(2.025 -1.000) .Sin (2 . +80)) + 0 = 14.126 m dH = hi  V – h = 1.25 + 14.126 - 1.515 = 13.861m RLA = RLTBM – hi V – h = RLTBM – dH = 50 – 13.861 = 36.139 m

  12. Thank You !

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