Which one of the following statements is CORRECT?a)The height of the instrument method is better as compared to the rise and fall method.b)The length of a metric used in levelling is 2.0 m.c)The rise and fall method for the reduction of levels provided checks on all sights.d)The effect of curvature is to cause the object to appear the same as they really are.Correct answer is option 'C'. Can you explain this answer?

Question

Answer

The correct statement is option C: The rise and fall method for the reduction of levels provided checks on all sights.

Explanation:
The rise and fall method is a commonly used method in surveying for determining the reduced levels of points. It involves taking readings of the staff at different points and applying corrections to account for errors and variations in the measurements. This method provides checks on all sights, ensuring the accuracy of the levelling process.

Here is a detailed explanation of the rise and fall method for the reduction of levels:

1. Procedure:
- The surveyor sets up the instrument at a known benchmark or reference point.
- The staff is placed at the desired points where readings are to be taken.
- The surveyor looks through the telescope of the instrument and reads the staff at each point.
- The readings are recorded, and corrections are applied to account for various factors.

2. Backsight and Foresight:
- The first reading taken on the staff is called the backsight. It is taken on a staff held at a point of known reduced level.
- The backsight reading helps to establish a starting point for the levelling process.
- The subsequent readings taken on the staff are called foresights. They are taken on staffs held at points whose reduced levels need to be determined.

3. Rise and Fall Calculation:
- After taking the backsight and foresights, the surveyor performs a calculation known as the 'rise and fall' to determine the reduced levels of the foresight points.
- The rise and fall is the algebraic sum of the differences between each foresight reading and the preceding backsight reading.
- This calculation ensures that any errors or mistakes in the readings are identified and corrected.

4. Accuracy and Checks:
- The rise and fall method provides checks on all sights, which means that the accuracy of the levelling process can be verified.
- By comparing the calculated reduced levels of the foresight points with their actual known reduced levels (if available), the surveyor can check for any discrepancies or errors.
- This helps to ensure the reliability and accuracy of the levelling results.

In summary, the rise and fall method in levelling provides checks on all sights, allowing for the verification and correction of errors in the readings. This makes it a valuable and widely used method in surveying.

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