Page 24 - ebook_soil engineering practical workbook_15112021

2.4 Safety Precautions

- Use the instrument properly and handle with care.

- Always make sure the instrument is clean after finished.

- Taking care of survey instruments and maintaining them in good
working condition.

2.5 Procedures

2.5.1 Setting up the Theodolite.

- Set tripod and instrument with optical plumb almost over the station.
- The theodolite is mounted on a tripod. First, extend the tripod legs,

splay them fully and push the ends firmly into the ground.
- Next look at the theodolite mounting platform. This should be

reasonably level and not too high nor too low for the users.
- Adjust the leg lengths until it is right then screw the theodolite onto the

platform.
- You may wish to set the theodolite up over a reference point on the

ground. In this case, you can use the sight on the front of the instrument
to view the point and adjust the theodolite’s position by slightly

unscrewing the mounting screw and moving the theodolite sideways.
Alternatively, you can ask a helper to push a nail or peg into the ground

under your guidance to fix a new reference point.

2.5.2 Levelling the Theodolite.

- There are 3 levelling screws at the base of the instrument. These should

be used with the round spirit level to obtain a coarse adjustment.
- When this is done, line the long spirit level with 2 of the levelling screws

and make the first fine adjustment.
- Then turn the theodolite through 90 degrees so the long spirit level is

pointing at the 3rd levelling screw and adjust that until it is level.

16 | Soil Engineering Practical Workbook