### What Is Reciprocal Leveling

### Reciprocal Leveling is a method of levelling to determine the difference of level between two points at a considerable distance apart with great precision.

### Reciprocal Leveling is also used when it is not possible to set up a level instrument.

fig 1. |

### PROCEDURE

Let A and B be the two points whose difference is to be determined.

i. Set the level instrument near A. Complete temporary adjustment and takes reading staff A and B. Write the reading like as a1 and b1. shown in fig. 1

fig 2. |

ii Transfer the instrument to B and set up near to B. Make a temporary adjustment. Take the staff reading as a2 and b2.

d= the true difference of level between A and B.

e= the total error due to curvature, refraction, and imperfect collimation adjustment.

The correct staff reading in fig.1= b1-e.

The correct staff reading in fig.2= a2-e.

In the fig.1 the true difference of level between A and B (true fall from A to B)

d= (b1-e)-a1

or d= (b1-a1)-e ....................................equation F

In the fig.2 the true difference of level between A and B (true fall from A to B)

d= b2-(a2-e) or

(b2-a2) +e ............................................equation G

Adding the equation Fand G to eliminate e, we get

d= (b1-a1)+(b2-a2)/2

Two values gives the true difference of elevation between two points free from all errors, like error due to curvature of the earth, refraction error and error of collimation error.

SEE ALSO:-https://www.technoupendra.com/2020/03/how-to-create-3d-surface-into-auto-cad.html

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