Question

Face Left and Face Right observations using a vernier theodolite will eliminate

• A. index error
• B. graduation error
• C. eccentricity error
• D. atmospheric error

Hint:

To eliminate index and graduation errors, always take measurements using both Face Left and Face Right positions to average out any systematic errors.

Answer 1

The Correct Option is A, B

In surveying, the use of a vernier theodolite involves measuring angles by observing them in two positions: Face Left and Face Right. This method is used to eliminate certain systematic errors. Step 1: Explanation of the options
- Option (A): Index error occurs due to the alignment of the instrument’s scale and the optical system. By taking readings in both the Face Left and Face Right positions, the index error is eliminated because any error present in one face will be counteracted by the opposite face.
- Option (B): Graduation error refers to errors that occur due to imperfections in the instrument’s graduation or scale. Similar to index error, switching between Face Left and Face Right will help eliminate this error, as the readings from both positions will average out the graduation error.
- Option (C): Eccentricity error occurs due to misalignment of the instrument’s center of rotation. This error is not eliminated by Face Left and Face Right observations, so this option is incorrect.
- Option (D): Atmospheric error is caused by the refraction of light through the atmosphere, but it is not eliminated by changing the face of the instrument. Atmospheric corrections typically require other methods, so this option is incorrect. Thus, the correct answers are (A) and (B).