TACHYMETRY

1. TACHYMETRY LESSON 5 Variable angle Tangential system

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

3. Principles The Tangential System of Tachymetry b s = the staff intercept AB V = the vertical component XY, the height of the centre hair reading above (or below) the instrument axis  ,b= vertical angle (variable) H = the horizontal distance required. hi = instrument height

4. Publication formula AY = H tan θ BY = H tan b AY –BY = s = H ( tan θ – tan b) H = s tan θ – tan b Horizontal distance

5. Where S = staff intercept H = horizontal distance V = vertical distance  = zenith angle ( > b) hi = the height of instrument (always positive) h = the centre hair reading ( @ b) RL= Reduced level

6. Work procedure EXAMPLE RESULT PRACTICAL 3 - TACHEOMETRY BOOKING FORM (The Tangential System )

7. Practical 3 • GIVEN THE TBM (Temporary bench mark) – Stn A & B • DETERMINING THE NUMBER OF STATIONS • READING VERTICAL ANGLE BELONG THE SITUATION • TRAVERSE METHOD • TAKE TOPOGRAPHY ITEMS (Tree, Building, Pedestrian)

8. Sketches topography B Tree 1 H = Va = Sa= Vb = Sb= B b2 H = Va = Sa= Vb = Sb= E Tree 2 H = Va = Sa= Vb = Sb= B E A b1 H = Va = Sa= Vb = Sb= A P2 H = Va = Sa= Vb = Sb= A P4 H = Va = Sa= Vb = Sb= b2 b4 A P6 H = Va = Sa= Vb = Sb= A D P2 b1 b3 P1 C B3 H = Va = Sa= Vb = Sb= C P1 H = Va = Sa= Vb = Sb= C P3 H = Va = Sa= Vb = Sb= C P5 H = Va = Sa= Vb = Sb= C P3 Pedestrian P4 P6 P5

9. Example for field book - topography

10. EXAMPLE CALCULATION H = s = (3.50 – 1.50) = 13.94 m tan θ – tan b tan +13 – tan+5

11. JIKA ADA MASALAH AMALI, Thank You!