Instrument required
Theodolite
Diagram
Procedure
- Settle the instrument at station ‘O’ and it was levelled accurately with reference to the altitude bubble.
- The zero of vertical vernier was exactly set to zero using vertical circle clamping screw and corresponding slow motion screw.
- The bubble of altitude level was brought at the centre. Thus the line of collimation become horizontal with respective the zero reading on the vernier.
- The vertical clamp screw was loosen and telescope was sighted in vertical plane to ‘P’. The accurate by section was obtained with the help of vertical circle tangent screw.
- The reading on both the vernier ( C and D ) where taken the mean of reading ‘C’ and ‘D’ required vertical angle.
- The face was change and another value of angle was obtained. Same procedure are required to obtained.
- The average vertical angle was obtained by taking mean of two values obtained with two faces.
