In this post we will explain that how to measure a bearing or Bearings Measurement . we will discuss with you bearing calculation method with the help of diagram.
How to Measure a Bearing / Bearings Measurement
MEASUREMENT OF BEARING ;-
In this method the bearing of all the lines are observed. This method is also know as fast needle method .following are three method for reading of bearing ;
1) To read bearing with transit of telescope .
2) To rad bearing without transit of telescope .
3) To read bearing by back-bearing method .
To read bearing with transit of Telescope ;
The detail of the method is as follows .
i. In this method first the theodolite is set at the point a , the zero of in venire is made coincident with the zero of he main scale of theodolite . theodolite is made to face the north with the help of the compass of the theodolite. This is the zero position of the theodolite.
ii. The telescope Is faced towards the next statin B by loosening the upper plate of theodolite . and the reading of the bearing of AB is taken . suppose this reading is 750.
iii. After this , the theodolite is set at the point B. at this time theodolite will give the previous reading of 75 degree . if it is changed a bit with the change of theodolite then it is corrected with the help of tangent screw.
iv. The telescope is faced toward the previous point A by loosening the lower plate of theodolite
v. Telescope is transited . even after transit its reading will be the previous one , e.g. , 75 degree .it is because the telescope is facing toward AB yet .
vi. The telescope is made to face the next point C by loosening its upper plate and turning the theodolite in the clockwise direction now the bearing of the line BC is read .
vii. The theodolite is shifted to the next point C and is set . then the telescope is turned towards the point B and it will show the previous reading .
viii. Telescope is transited first . even after transit is reading will the previous one i.e that of BC . then the telescope is faced toward the pint B by turning the telescope clockwise by loosening the upper plate . and the bearing of CD is found out . similarly the bearings of all the lines are read .
To read bearing without transit of telescope ;-
This is like similar to the above method with the difference that the telescope is not transited . due to this at the even numbered stations need correction at 180 degree . at the even numbered stations i.e. second fourth sixth etc. if the angle is more than 180 degree then 180 is subtracted form them .while if this reading is less than 180 degree then 180 is added to it. This method is considered better than the previous method , because instrumental errors are less here .
To read bearing by Back-Bearing Method ;-
Method of taking reading is explained as follows ;
i. In this method , theodolite is set at the first point A. then the bearing of the line AB is read .
ii. Then theodolite is set at the point B.
iii. Theodolite reading is set equal to that back bearing the line AB .Now the two plates are locked.
iv. Telescope is faced toward the previous point A by loosening the lower plate . this makes the orientation of telescope correct .
v. Telescope is faced toward the next point V by loosening the upper plate and the bearing of line BC is read .
vi. The theodolite is set at the next point C. Theodolite reading is set equal to that back bearing of the line BC by setting the telescope facing B. the telescope is turned to the next point D and the bearing of line CD is read . similarly the bearing of the other lines are read.
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