Page 27 - ebook_soil engineering practical workbook_15112021

2.7 The following steps for measuring the face right observation.
i. Loosen the upper clamp and the telescope clamp. Rotate the theodolite

circle in a clockwise direction and make sure the vertical circle on the

right of the observer. Bisect the station A.
ii. Tighten the upper clamp screw. Point A should be brought into exact
coincidence with the point of intersection of the horizontal and vertical

cross-hairs by using the vertical circle clamp and tangent screw. The value
o
of horizontal angle can be obtained by deducting 180 00’ 00”.
iii. Loosen the upper clamp and set the telescope to bisect station C. Fix the
upper clamp and bisect C exactly by using the upper slow motion. Record

the C reading.

2.8 Project : Training of temporary adjustment and measuring horizontal angle

measurement

 Station 1,2, 3 and 4 is the station points fixed on the ground by a pegs.

Set a the theodolite over the peg at station 2 and level it accurately.
 Station 1 and 2 is the station fixed on the ground by a three ranging

rods and plumb.
 Repeat the process to measure the horizontal angles for station 1, 2,3

and 4. The distance for each station to be measured by using a tape.
 The average horizontal angle is then obtained by taking the average of

two angles obtained with face left and face right.
 Usually four repetitions of face left and four repetitions of face right

should be taken
 Record the readings and the mean angle should be calculated.

Station 1
Station 4

Station 2 Station 3

Figure : Closed Traverse

19 | Soil Engineering Practical Workbook