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Levelling | Purpose | Terminologies

Keywords: Levelling, Surveying, Dumpy level, benchmark, Mean Sea Level, M.S.L, Elevation, G.T.S benchmarks, arbitrary benchmarks, datum, Bombay port, Reduced level, Survey of India

What is Levelling?
Levelling is defined as the process of determining the relative heights or elevations of points or objects on the earth’s surface. The elevation of a point is defined as its vertical distance measured above or below a reference level which is called datum. The most widely used datum surface is the Mean Sea Level, M.S.L

Levelling instrument: Dumpy level
Levelling instrument: Dumpy level (Source: Wikimedia Commons)

Purpose of leveling
Leveling is done for all important engineering works and construction projects. Some of the purposes for which leveling is done are listed below:

Terminologies in Levelling

Different types of BMs are established and used depending on the permanency and the precision required. They are as follows:

Most of the leveling work can be done assuming an arbitrary benchmark. This is because for most of the applications only the difference of elevations is needed. The point chosen for an arbitrary benchmark should be chosen such that none of the RLs become negative, which leads to confusion in the calculation.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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