Theory

For measuring bearing a through compass or tabular compass is attached to the theodolite at the place provided for compass


Instrument required

1.      Theodolite

2.    Tripod

3.    Plumb bob

4.    Ranging rod
Diagram



Sr. no.
object
face
Reading on A
Reading on B
Differance
Angle
1
Ranging rod

72014’20”
25014’20”
18000’0”
72014’20”


Procedure

  • Set up theodolite over and level accurately.

  • Set the vernier A at 0-0 of horizontal angle.

  • Looses the lower clamp magnetic needle is than released to swing on the point of the compass. Locate the instrument about it outer axis until the magnetic needle roughly points to the north. Clamp the lower plate and by turning the lower tangent screw being the needle exactly against the mark on showing in fig.

  • Losses the upper clamp and direct the theodolite towards ‘B’ and bisect it exactly by using upper clamp and tangent screw. Read both vernier A and B.

  • Change the face and repeat the procedure. The average of the two values given the correct bearing.



To set up straight line

  • Set up the theodolite at ‘A’ and level it accurate bisect ‘B’ exactly and establish a point ‘C’ in the line beyond ‘B’

  • Shift the instrument to bisect ‘C’ and establish a point ‘O’ in the beyond ‘C’

  • Continuous the process until the loss point ‘P’ is marked.