## Adjustment of Level
Definition (1 mark)
Adjustment of level is the process of making the levelling instrument perfectly horizontal and free from errors so that accurate staff readings can be taken.
Temporary Adjustment of Level (2.5–3 marks)
Temporary adjustments are performed at every instrument setup:
1. Setting up the Level
- The instrument is fixed on the tripod.
- The tripod is placed firmly on the ground.
2. Levelling Up
- The foot screws are adjusted to center the bubble.
- The bubble is brought to the center in all directions.
- This ensures the line of sight is horizontal.
3. Focusing
- The eyepiece is focused to see cross hairs clearly.
- The objective lens is focused on the staff to remove parallax.
Permanent Adjustment of Level (2.5–3 marks)
Permanent adjustments are done occasionally to maintain accuracy:
1. Adjustment of Bubble Tube
- The bubble axis is made parallel to the line of sight.
2. Collimation Adjustment
- Ensures that the line of sight is truly horizontal when the bubble is centered.
3. Two-Peg Test
- A practical test used to check and correct collimation error.
Key Concept
- Proper adjustment ensures that the line of sight remains horizontal, which is essential for correct determination of elevation differences.
Conclusion (1 mark)
Adjustment of level is essential to ensure accuracy in levelling work, as it maintains a true horizontal line of sight and eliminates instrumental errors.
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