## Friday, April 1, 2011

Aim :
To determine the gradient of the line joining two staff stations ( A and B).

Instruments Required :
Tacheometer, Levelling Staff.
Given : R.L. of Bench Mark = 100.000

Procedure :
1.      Set up the instrument approximately between the given objects and do the initial adjustments.
2.      Take horizontal angles, vertical angles, stadia readings in both the faces and swings.

Calculation :
Case : I
When the observed vertical angle α is of an angle of elevation
V= The vertical distance from the instrument axis to the point C.
V=D tan a

D = KS cos2a + C cosa
R.L. of A = R.L. of H.I. + V - h
where,
R.L. of H.I. = Elevation of B.M + Back sight (h0)

Case II
When the observed vertical angle is an angle of depression.
R.L. of A = R.L. of H.I. - V - h

Case : III
When the observed vertical angle is zero.
R.L. of A = R.L. of H.I. - h
AB = ÖD12 + D22 – 2D1D2 cosq

Result:
The gradient of the line joining A and B =

DETERMINATION OF THE GRADIENT OF THE LINE
 Face : Right                                         Swing :  Left Inst at Sight to Statia hair reading Vertical angle Horizontal angle C D Mean A B Mean Top Mid Bot o , ,, , ,, o , ,, o , ,, , ,, o , ,, O A B Face :   Left                                         Swing :  Right O A B