Adjustment of Theodolite
Theodolite is a precision instrument used for measuring horizontal and vertical angles. For accurate results, it is necessary to properly adjust the instrument before taking observations. Adjustments of a theodolite are classified into temporary adjustments and permanent adjustments. In ITI Draughtsman Civil, understanding these adjustments is essential for correct surveying work.
1. Temporary Adjustments
Temporary adjustments are made at every station before taking readings. These adjustments prepare the instrument for use.
(a) Setting Up
- Fix the theodolite on the tripod stand.
- Spread the tripod legs firmly on the ground.
(b) Centering
- Place the instrument exactly over the station point.
- Use plumb bob or optical plummet.
(c) Levelling
- Use levelling screws to center the bubble.
- Ensure the instrument is perfectly horizontal.
(d) Focusing
- Adjust eyepiece to make crosshairs clear.
- Focus the objective lens for a sharp image.
2. Permanent Adjustments
Permanent adjustments are made occasionally to maintain the accuracy of the instrument. These ensure the correct relationship between fundamental lines.
Main Permanent Adjustments
(a) Plate Level Adjustment
- Ensures plate level axis is perpendicular to vertical axis.
(b) Collimation Adjustment
- Ensures line of collimation is perpendicular to horizontal axis.
(c) Horizontal Axis Adjustment
- Ensures horizontal axis is perpendicular to vertical axis.
(d) Telescope Level Adjustment
- Ensures line of sight is horizontal when bubble is centered.
3. Importance of Adjustments
- Ensures accurate measurement of angles.
- Maintains proper functioning of the instrument.
- Reduces errors in surveying.
- Improves reliability of data.
4. Precautions
- Always perform temporary adjustments before use.
- Handle the instrument carefully.
- Check leveling and centering properly.
- Avoid disturbances during observation.
Role of Draughtsman Civil
A Draughtsman Civil uses theodolite data for preparing layouts and construction drawings. Proper adjustment ensures accurate data collection and precise plotting.
Conclusion
Adjustments of theodolite are essential for accurate surveying. Temporary adjustments are done at every setup, while permanent adjustments maintain long-term accuracy.
For ITI Draughtsman Civil students, understanding these adjustments is important for effective use of theodolite and successful surveying work.