Engineering knowledge

Dumpy Level RL Calculation Easy Formula

In leveling using a Dumpy Level, RL (Reduced Level) is calculated mainly by the Height of Instrument (HI) Method.

1️⃣ Height of Instrument Formula

HI = RL (Benchmark) + Back Sight (BS)
HI = Height of Instrument
RL = Reduced Level of Benchmark
BS = Back Sight reading

2️⃣ Reduced Level Formula

RL = HI − Staff Reading
Staff reading can be:
IS = Intermediate Sight
FS = Fore Sight
So the formula becomes:
RL = HI − IS
RL = HI − FS

3️⃣ Example Calculation

Benchmark RL = 100.00 m
Back Sight (BS) = 1.50 m
HI = 100.00 + 1.50 = 101.50 m
If Intermediate Sight (IS) = 1.20 m
RL = 101.50 − 1.20 = 100.30 m
If Fore Sight (FS) = 1.80 m
RL = 101.50 − 1.80 = 99.70 m

4️⃣ Leveling Check Formula

ΣBS − ΣFS = Last RL − First RL
This formula is used to check leveling calculations.

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