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Friday, April 1, 2011

DETERMINATION OF GRADIENT OF THE LINE BY TANGENTIAL METHOD


DETERMINATION OF GRADIENT OF THE LINE
BY TANGENTIAL METHOD

Aim :

            To determine the gradient of the line joining the given staff stations A and B.

Instruments Required :

            Theodolite, Ranging rods, Levelling staff

Given :

            Elevation of B.M. = 100.000
            Target distance = 1m.

Procedure :

1.      Set up the instrument approximately between the given objects and do the initial adjustments.
2.      Direct the telescope towards object A and find the vertical angles by bisecting the ranging rod at two points having a distance of lm(given).
3.      Note down the vertical angles for the ranging rod at B.
4.      Take the horizontal angles also at A and B.
B.M.
 
B
 
s2
 
h2
 
V2
 



            When both the observed angles are angles of elevation
            B.M. = 100.000m
            S = 1 m = Target distance
            a1 & a2 = Vertical angle to upper and lower targets respectively.
            h1 = Height of lower target above foot of ranging rod
            h0 = Height of instrument above datum line

            D = Horizontal distance between P and A = 
            V = D tan a2
            R.L of H.I  = R.L. of B.M. + h0
            R.L. of A = R.L. of H.I + V1- h1

            D2 = D12 + D22 – 2D1D2 cosq
            V0 = Level difference between A & B
            Gradient =

Result :

            The gradient of the line joining A and B =


TANGENTIAL TACHEOMETRY

Face :  Right                                        Swing :  Right
Inst at
Sight to
Position of vane
Vertical angle
Horizontal angle
C
D
Mean
A
B
Mean
o
,
,,
,
,,
o
,
,,
o
,
,,
,
,,
o
,
,,
P
A
Top vane


















Bottom vane

















B
Top vane


















Bottom vane
















Face : Left                                           Swing :   Left
P
A
Top vane


















Bottom vane

















B
Top vane


















Bottom vane


















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