Ad. sur. repetition method (gtu) (1)

Measurement of Horizontal Angle in Advance Surveying

General method
Repetition method

1. Measurement of Horizontal Angle in Advance Surveying By Abhishek Sir ‹#› Rocket Education

2. Methods to measure Horizontal Angle There are three methods to measure horizontal angle by theodolite : General Method Repetition Method Reiteration Method ‹#›

3. General Method Let angle PQR is to measured Set up the instrument at the stations Q. Centre it and level up accurately. Release both clamp screws. Make the instrument Zero-Zero. Make the vertical circle at the left side. Take the reading on both A and B vernier. It must be 0,0’0’’ and 180’0’0’’. Now loose the lower clamp screw and turn the telescope towards P. P Q R ‹#›

4. General Method Bisection point P accurately by using lower tangent screw. Check the reading on verniers A and B. The reading on A will be 0’ and on B will be 180’. Now tight lower clamp screw and loose upper clamp screw. Turn the telescope clockwise until the line of sight is on the signal at R. Tighten the upper clamp screw. By turning the upper clamp screw, bisect the signal R exactly. Read both the verniers. The reading of the venire A give the value of the angle POR. The vernier B gives the value of angle PQR after deducting 180’. ‹#›

5. 2. Repetition Method This method is used to measure a horizontal angle very accurately. By this method, the angle is measured two or more times and the value is added mechanically. The horizontal is equal to the accumulated value divided by the number of repetitions made. Set up the instrument at the stations Q. Centre it and level up accurately. Release both clamp screws. Make the instrument Zero-Zero. Make the vertical circle at the left side. Take the reading on both A and B vernier. It must be 0,0’0’’ and 180’0’0’’. Now loose the lower clamp screw and turn the telescope towards P. ‹#›

6. 2. Repetition Method Bisection point P accurately by using lower tangent screw. Check the reading on verniers A and B. The reading on A will be 0’ and on B will be 180’. Now tight lower clamp screw and loose upper clamp screw. Turn the telescope clockwise until the line of sight is on the signal at R. Tighten the upper clamp screw. By turning the upper clamp screw, bisect the signal R exactly. Read both the verniers. Now, tight the upper clamp screw and loose the lower clamp screw. Rotate the telescope towards the P side with clockwise direction and bisection point P accurately by using lower tangent screw. ‹#›

7. 2. Repetition Method Now repeat steps 7 to 10 two times and the final reading in virner is almost thrice the angle. Divide the angle by three and you will get your final angle. Change the face of the instrument right face. The telescope will be in the inverted condition . Repeat the steps 2 to 9 and determine the angle with right face. Determine the average value of the angle obtained with the right face and left face and final angle PQR. ‹#›

8. ‹#› Thank You