1. “In Pursuit Of Global Competitiveness”
Government College Of Engineering,
Aurangabad.
 Created By:-
Nikhil Pakwanne

2.  It Is Also Called RANKINE’S
METHOD.
This method also follows the
centerline of the curve.

3.  This method is based on the following
geometry:

4.  Let AB & BC be two tangent intersecting
at B, the deflection angle be  (shown in
fig.)
 the tangent length is calculated &
tangent pt.T 1, T 2 are marked.
 Let,
P1 = first pt. on the curve.
T 1P1 = l1 length of cord.
 1 = deflection angle for first chord.
R = radius of curve
n = total deflection for the chord.

5.  Here,
T 1OP1  2  BT1P1  2 1
 Again,
Chord T 1P1  arc T 1P1
 Now,
T 1OP1 360

l1 2R
360  l1
 2 1 
2R

6.  OR,
360  l1
 1  Degrees
2  2R
360  60  l1
 1  min s
2  2R
1718.9  l1
 1  min s
R
 simillarly,
1718.9  l 2
 2  min s
R
1718.9  l 3
 3  min s
R

7.  then,
1718.9 ln
δn  min
R
 when the degree of curve D is given,
D  l1
 1  Degrees
60
Dl2
 2  Degrees
60

8.  finally,
D  ln
δn  deg
60
 Arithmetical check:

 1   2   3  ..... n  n 
2

9.  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.

10. 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.

11.  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.

12. SURVEYING AND
LEVELLING BY N.N.
BASAK
http://en.wikipedia.org

13. Appreciate
your time and attention!