Section 4: Soil and Water Conservation Engineering
Surveying and Levelling
Subtopic: Types of levelling
Question Statement:
For a long sight distance of $d = 2.0\text{ km}$ across a reservoir, the combined correction for the Earth's curvature and atmospheric refraction ($C_{cr} = 0.0673 d^2$, where $d$ is in km and $C_{cr}$ in metres) in metres is ________ (round off to 3 decimal places).
Answer Key:
0.269
Step-by-Step Solution & Explanation
The combined curvature and refraction correction is:
$C_{cr} = 0.0673 \cdot d^2$
Where $d = 2.0\text{ km}$:
$C_{cr} = 0.0673 \times (2.0)^2 = 0.0673 \times 4.0 = 0.2692\text{ m} \approx 0.269\text{ m}$