Object: To determine the vertical and horizontal angle of a line, as well as the bearing of the line with the help of digital or electronic theodolite.

Equipment:

Digital theodolite, tripod stand, leveling staff, ranging rods, plum bob, prismatic compass, and tape.

Theory:

Angle:

An angle is the figure formed by two lines, called the sides of the angle, sharing a common endpoint.

Horizontal Angle:

An angle between two lines, which are on the horizontal plane, called horizontal angle.

Vertical Angle:

An angle formed by two lines, which are on the vertical plane, is called a vertical angle.

Bearing:

Bearing is defined as direction of line measured with respect to meridian.

Magnetic Bearing: Magnetic Bearing is defined as direction of line measured with respect to magnetic north.

Fig: 03.1 Measurement of horizontal angle

Procedure:

Measuring the horizontal angle BAC

1. Mark station A set up the instrument at station A and level it accurately.
   
2. Then mark two more stations B and C at some distance from station A.
   
3. Horizontal clamp is kept fixed and vertical clamp loosened, then set telescope at 90˚ with the help of vertical clamp and vertical screw.
   
4. Now the vertical clamp is tightly fixed and horizontal clamp is loosened and telescope is directed towards B and bisect the ranging rod at B.
   
5. Horizontal clamp is fixed and set horizontal angle as 0˚ by using reset button.
   
6. Now loose the horizontal clamp and telescope is directed towards C and bisect the ranging rod at C.
   
7. Finally note the horizontal angle from display screen.
   

Measuring the vertical angle:

Fig: 03.1 Measurement of vertical angle

1. Set up the instrument at any station from building is visible and level it accurately.
   
2. After setting, set the vertical angle as zero degrees and lock the vertical clamp screw.
   
3. Till the telescope of theodolite to the top of building.
   
4. Note the vertical angle that is displayed on the digital screen name it as ϕ.
   
5. Calculate vertical angle θ by using the formula “ θ = ϕ – 90˚ ”.
   

Measuring the Magnetic bearing of a line:

In order to measure the magnetic bearing of a line, the theodolite should be provided with prismatic compass.

The following are the steps:

1. Mark station A then mark North with the help of prismatic compass at station A.
   
2. Then mark two more stations B and C at some distance from station A.
   
3. Set up the instrument at station A and level it accurately.
   
4. Horizontal clamp is kept fixed and the vertical clamp is loosened, then set telescope at 90˚ with the help of the vertical clamp and vertical screw.
   
5. Now the vertical clamp is tightly fixed and horizontal clamp is loosened and telescope is directed towards north and bisect the ranging rod.
   
6. Horizontal clamp is fixed and set horizontal angle as 0˚ by using reset button.
   
7. Now loose the horizontal clamp and telescope is directed towards B and bisect the ranging rod at B.
   
8. Note the H.A. displayed at display screen, which is the bearing of line AB.
   
9. Again telescope is directed towards north and bisect the ranging rod then Horizontal clamp is fixed and set horizontal angle as 0˚ by using reset button.
   
10. Loose the horizontal clamp and telescope is directed towards C and bisect the ranging rod at C.
    
11. Note the H.A. displayed at display screen, which is the bearing of line AC.
    
12. And also measure distances of AB and AC with the help of tape.
    

Fig: 03.1 Measurement of Magnetic bearing angle

Observation:

AutoCAD Graph: