Advance Survey-Unit 1 (part-2)// Online 5th Semester Free Coaching// JUT Syllabus

Setting out of Curve
PROCEDURE: -
To set out the curve,
Divide the long chord into an even number of equal parts.
Set out the offsets as calculated from formula at each of the points of division, thus obtaining the required points on the curve. Since the curve is symmetrical along ED, the offsets for the right half of the curve will be same as those for the left half.
If the offsets are calculated from formula the long chord should be divided into a convenient number of equal parts and the calculated offsets set out at each point of division.
This method is usually adopted for setting out short curves.
1. RANKINE’SMETHODOFTANGENTIALANGLE: -
In this method the curve is set out by the tangential angles (often called the deflection angles) with a theodolite and a chain or tape.
The derivation of the formula for calculating the deflection angle it as fallows
Let,
AB=the rear tangent to the curve.
T1 and T2 = the tangent points
D, E, F, etc. = the successive points on the curve.
δ1, δ2, δ3, etc = the tangential angles which each of the successive chord T1D, DE .EF etc makes with the respective tangents at T1, D ,E, etc.
Δ1, Δ2, Δ3, etc = the total tangential or deflection angles (between the rear Tangent AB and each of the linesT1D, DE, EF, etc.
c1, c2, c3 etc = the lengths of the chord T1D, DE, EF, etc.
R = radius of the curve
Chord T1D = arc T1D (very small) = c1.

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