Government College Of Engineering, Aurangabad.

“In Pursuit Of Global Competitiveness”

Simple Circular Curve-Angular Method

Created By:-

Nikhil Pakwanne

SETTING OUT - DEFLECTION ANGLE METHOD :-

It Is Also Called RANKINE’S METHOD.

This method also follows the centerline of the curve.

This method is based on the following geometry:

Let AB & BC be two tangent intersecting at B, the deflection angle be (shown in fig.)

the tangent length is calculated & tangent pt. are marked.

Let, = first pt. on the curve. = length of cord. = deflection angle for first

chord. R = radius of curve = total deflection for the

chord.

2,1 TT

1P11PT 1l1

n

Here,

Again, Chord arc

Now,

11111 22 PBTOPT

11PT 11PT

Rl

OPT

2

360

1

11

R

l

2

3602

11

OR,

simillarly,

DegreesR

l

22

360 11

sR

lmin

22

60360 11

sR

lmin

9.1718 11

sR

lmin

9.1718 22

sR

lmin

9.1718 33

then,

when the degree of curve D is given,

minR

l1718.9δ

n n

DegreeslD

60

11

DegreeslD

60

22

finally,

Arithmetical check:

deg60

lDδ

n n

2.....321

nn

Procedure:-

i. Set the instrument up at the tangent point, sight along the tangent and turn off the first deflection angle ( Φ =Ө/2 ).

ii. fix one end of tape at A, measure off 'c' meters, and swing tape until it aligns with the line of sight. Put in peg B.

iii. Turn theodolite a further Φ°. Fix one end of tape at B, measure off 'c' meters, and swing tape until that point on the tape crosses the line of sight. Put in peg C.

iv. Repeat step (iii) until you peg the curve. If the line of sight becomes obstructed, then simply set up on any peg on the curve, sight back along the chord to the previous peg and

continue to establish the deflection angles.

Precautions to take:

Calculate the angle Φ to seconds, or errors will be considerable

if many pegs must be placed.

The final reading, to the other tangent point, should equal L.

SURVEYING AND LEVELLING BY N.N. BASAK

http://en.wikipedia.org

REFERENCES

Thank You

Appreciate your time and attention!