A back sight reading on BM = 100 m was 2.67 m. The inverted staff reading to the bottom of a girder was 1.5 m. The RL of the bottom of girder is:

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BHEL Engineer Trainee Civil 24 Aug 2023 Official Paper

Answer 1

Concept:

To find the RL (Reduced Level) of the bottom of the girder using an inverted staff reading, we follow these steps:

First, calculate the Height of Instrument (HI) using:

\( HI = RL_{BM} + BS \)

Given:

RL of BM = 100.00 m

Back sight (BS) = 2.67 m

Inverted staff reading to bottom of girder = 1.5 m

Step 1: Find HI

\( HI = 100.00 + 2.67 = 102.67 \, \text{m} \)

Step 2: Use inverted reading to calculate RL of bottom of girder

Since the staff is held inverted, the reading is added to HI:

\( RL = HI + 1.5 = 102.67 + 1.5 = 104.17 \, \text{m} \)