This method is used if there are more than one angles to be measure from a certain station point. Consider the following fiqure, we will measure angles AOB and BOC using this method.
Procedure- Setup the theodolite at station O, bisect the point A with a certain circle reading with face left.
- Rotate the instrument in clockwise direction and bisect B, note the circle reading.
- Then rotate and the telescope till it bisect the point C, note this circle reading also. All these reading will book into face left position.
- Transit the telescope and rotate the instrument through 180°, this time bisect the point C firstly and then rotate telescope in anti clockwise direction towards B and then ultimately towards A. Put these readings in face right position.
- You can do more than one sets of measurements for the accurate results, i have done one set and booking method is as follows,
Inst. StationStn. SightedFaceCircle reading(° ′ ″)Mean of faces(′ ″)Angle value(° ′ ″)OAL10 20 5020 60AOB37 10 05
R190 20 07
BL47 30 1030 11
R227 30 12BOC41 10 14
CL88 40 2040 25
R268 40 30
