Difficulty: Easy
Correct Answer: All of the above
Explanation:
Introduction / Context:
Theodolites measure horizontal and vertical angles precisely. Their accuracy depends on strict geometric relationships among three axes: the telescope (line of collimation) axis, the transit (trunnion) axis, and the vertical (rotation) axis. Understanding these relationships is vital for adjustments and reliable observations.
Given Data / Assumptions:
Concept / Approach:
For perfect adjustment: (1) the telescope axis must be perpendicular to the trunnion axis so that elevation motion does not skew the line of sight; (2) the vertical axis must be perpendicular to the trunnion axis so that the vertical circle plane is truly vertical; and (3) all three axes intersect at the instrument’s center, ensuring consistent geometry during rotations and transits.
Step-by-Step Solution:
Verification / Alternative check:
Face-left and face-right readings of the same angle should agree within tolerance; discrepancies indicate axis misalignment.
Why Other Options Are Wrong:
Each of A–C is individually correct, but only D states the complete set required for proper theodolite geometry.
Common Pitfalls:
Assuming leveling alone guarantees perfect geometry; internal axial relationships still require testing and, sometimes, adjustment.
Final Answer:
All of the above
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