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Write short note on profile levelling?
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Definition- The process of determining the elevation of a point at a measured interval along a fixed line such as the centre line of a railway, highway, canal or sewer is known as profile levelling.

Objects- Following are the object of profile levelling. To determine the undulation of ground along a given line for the alignment of a canal, pipeline, road and railway.

Procedure- Suppose AB, BC, CD, and DE is the direction of the centre of the road. The levelling instrument is placed at suitable position (say L1, L2, L3 ……..) and, after temporary adjustment, the staff reading are taken. The first staff reading of any set up is entered in a BS column, and last is the FS column. The other reading are entered in the IS column. The Fore bearing and back bearing of each line should be measured and enter in a level book.

Temporary BM should be placed at some chainage interval on the root of the tree or permanent points.at the end of day work, temporary BM is placed at a suitable point. Fly levelling should be done to connect this TBM to the starting point of the day work. At the point of fly levelling, all the TBMs are also connected in order to detect the place of error. The next day work is started from the TBM placed on the previous day.

Check:

∑BS-∑FS

∑Rise-∑Fall

Last RL – first RL

graph

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