Correct Answer - Option 4 : Bringing the vertical axis of the theodolite exactly over the station mark
The adjustments in transit Theodolite are of two types:
1. Permanent Adjustments.
2. Temporary Adjustments.
The permanent adjustment are made to establish the fixed relationships between the fundamental lines of the instrument, and once made, they last for long time. The following are the permanent adjustments in transit Theodolite:
- Adjustment of the Horizontal Plate Levels.
- Collimation Adjustment: Axis of the telescope level adjusted to parallel to the line of collimation.
- Horizontal Axis Adjustment: Horizontal axis is perpendicular to vertical axis when the instrument is leveled.
- Adjustment of the Telescope Level or the Altitude level.
- Vertical Circle Index Adjustment
The temporary adjustments are made at each set up of the instrument before starting taking observations with the instrument. The following are the temporary adjustments in transit Theodolite:
- Setting up the Theodolite over the station.
- Leveling up the Theodolite.
- Elimination of the parallel.