Section 4: Soil and Water Conservation Engineering
Levelling, Contouring & Earthwork Volume
Subtopic: Reduced level using Height of Instrument
Question Statement:
A levelling survey is conducted starting from a benchmark (BM) having reduced level $RL = 100.00\text{ m}$. The backsight reading on the BM is $1.950\text{ m}$ and foresight reading on station A is $2.150\text{ m}$. The reduced level of station A is ________ $\text{m}$ (round off to two decimal places).
Answer Key:
99.80
Step-by-Step Solution & Explanation
Using Height of Instrument ($HI$) method:
$HI = RL_{BM} + BS = 100.00 + 1.950 = 101.950\text{ m}$
Reduced Level of station A:
$RL_A = HI - FS = 101.950 - 2.150 = 99.800\text{ m}$
Rounding to two decimal places: $99.80\text{ m}$.