Basic principles of theodolite traversing
Basic principles of theodolite traversing Theodolite is an instrument designed for the measurement of the horizontal and vertical angle.It is most precise method it is also used for laying of horizontal angles Locating points on line prolonging the survey line establishing the gradient, determination of the difference in the elevation setting out a curve.
1) Set up the theodolite at station point O and level it accurately with reference to the altitude level. 2) Set vertical verniers C and D exactly to zero by using the vertical circle clamp and tangent screw, while the altitude level should remain in the center of its run. Also, the face of the theodolite should be left.
3) Release the vertical circle clamp screw and rotate the telescope in a vertical plane so as to bisect the object M. tighten the vertical circle clamp and exactly bisect the object by a slow-motion screw. 4) Read both verniers C and D. the mean of the two readings gives the value of the required angle.
5) A similar observation may be made with another face. The average of the two values thus obtained gives the value of the required angle which is free from instrumental errors.
6) Similarly, the angle of depression can be measured following the above steps. To measure the vertical angle between two points L and M Sometimes it is required to measure the vertical angle between two points L and M. There can be three possibilities.
(a) One point is above the line of sight and the other is below the line of sight then angle LOM as shown in fig will be equal to (<α +<β )
(b) Both the points are above the line of sight. Then the angle LOM= <α -<β (Refer Fig 2)
(c) Both the points are below the line of sight, then the angle LOM= <α -<β (Refer Fig 3) To measure the angle between two points L and M proceed as follows
1) Set the theodolite at station point O and accurately level it.
2) Bisect the flag at L as explained already and take the reading on the verniers C and D. Calculate the mean angle.
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