Short Note on Setting Out of Circular Curve by Theodolite and Tape Method.

Setting Out of Circular Curve by Theodolite and Tape Method.

i) First of all the tangential angles δ 1 , δ 2 , δ 3 etc are calculated by the formula given below.

δ1 = 1718.9 X C1__ minutes

R δ 2 = 1718.9 X C2 __ minutes

R δ 3 = 1718.9 X C3 __ minutes and so on R

Also the total deflection angel

for the 1st Chord 1 = δ 1

For 2nd chord 2 = δ 1 + δ 2

For 3rd chord 3 = δ 1 + δ 2 + δ 3

ii) Then set up a theodolite over the first tangent Point T1 and level it.

iii) With both the plates clamped at Zero, dissect the telescope to the ranging rod at the point of intersection B and bisect it.

iv) Release the vernier plate and set the vernier A to the first deflection angle 1 , the telescope being thus directed along T1 D.

v) Pin down the Zero end of the chain or tape at T1 , and holding the arrow at a distance on the chain equal to the length of the 1st chord (C1 ) swing the chain around T1 until the arrow is bisected by the cross hairs, thus fixing the 1st point D on the curve.

vi) Unclamp the upper plate and set the vernier to the second deflection angle 2 , the line of sight being now directed along T1 E.

vii) Hold the Zero end of the chain at D and swing the other end around D until the arrow held at a distance equal to the length of 2nd chord C2 , is bisected by the line of sight, thus locating the 2nd point E on the curve.

viii) Repeat the process until the end of the curve is reached