A hand level is a small levelling instrument that is held in hand when used for levelling. It consists of a rectangular tube, 100 to 150 mm long.
A small level tube is mounted on the top of the tube. There is a small opening in the tube immediately below the level tube. The lower and upper surfaces of the level tube are transparent. Inside the rectangular tube and to one side of it immediately. Under the opening, there is a reflecting mirror set an angle off 45o to the main length of the tube.
Also Read: Terms used in Levelling Survey
Use of Hand Level with procedure
The hand level is used for an approximate determination of elevations in reconnaissance, preliminary surveying, for locating contours on the ground, and for taking short cross-sections in profile levelling.
The following procedure is used for determining the difference of levels of two points.
- Hold the hand level in one hand at the eye level.
- Sight the staff held at the benchmark ór a point of known elevation.
- Raise or lower the objective end of the hand level utill the image of the bubble as seen in the reflecting mirror is bisected by the cross-hair.
- Take back sight reading against the staff held at the B.M
- Shift the staff to point B whose elevation is required and take foresight.
- Determine the level of the point B, as in differential levelling.
|RL of required point = (R.L. of B.M. + BS.) – F.S.|
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