Over Head Sign Board

When we pass on by a National Highway you can find Over Head sign Board,which normally give message to the drivers about the route,diversions etc.







But the road network may have some diversion to city and one may be towards the destination, some times the road network may be blocked due to some traffic accident but practically the message may not reach the driver one who move on that road network this problem can be rectified by using variable message sign which gives message to the driver when he is about to cross the diversion point. This application helps in making the driver to travel toward that accident point or blocked area.
--Electronic Traffic Sign often used on roadways to give travelers information about special events

1. The theodolite is mounted on the tripod stand.
2. The theodolite is centered over one of the given stations P from where the other given inaccessible station R and the staff station G can be sighted without any obstruction. The instrument is levelled using the foot screws and the altitude bubble is brought to the centre of its run.
3. Station R is sighted through the telescope.
4. The central vertical cross hair is made to bisect the station R and the central horizontal cross hair is made tangential to the top most point of the station R.
5. The vertical circle is read and the vertical angle is recorded.
6. The theodolite is then turned and the staff station G is sighted.
7. The line of sight is made horizontal by setting both the verniers C and D on the vertical circle at 0°00’00” and the staff reading on station G is observed and recorded.
8. Another instrument station Q is selected 20 m away from P and in line with station P and R on the same vertical plane by reversing the line of sight at P.
9. The theodolite is shifted and the centered over the station Q. The instrument is levelled using the foot screws and the altitude bubble is brought to the centre of its run.
10. Station R is sighted again through the telescope.
11. The vertical angle is read and the vertical angle is recorded by repeating the above procedure.
12. The theodolite is then turned and the staff station G is sighted.
13. The staff reading on G is observed and recorded after making the line of sight horizontal following the above procedure.
14. The horizontal distance between the two given stations P and R and the elevation of station R are determined from relevant trignometric expressions.

1. Horizontal Distance PR =
2. Elevation of R =

1. The theodolite is mounted on the tripod stand.
2. The theodolite is centered over an arbitrarily selected station P from where the staff stations A and B can be sighted without any obstruction and the instrument is levelled using the foot screws and both the plate bubble and the altitude bubble are brought to the centre of their run.
3. The theodolite is set on the face right mode and the vernier A on the face right mode and the vernier A on the horizontal circle is initially set at 0°00’00” and the staff station A is sighted.
4. The central vertical cross hair is made to bisect the staff station A and the central horizontal cross hair is made tangential to 2.5 m mark on the staff station.
5. The horizontal and vertical angles are recorded by reading the horizontal and vertical circles respectively.
6. The stadia hair readings for the staff station A are also observed and recorded.
7. The theodolite is swing to the right and the staff station B is sighted.
8. The central vertical cross hair is made to bisect the staff station B and the central horizontal cross hair is made tangential to 2.5 m mark on the staff station B.
9. The horizontal and vertical angle are recorded by reading the horizontal and vertical circle respectively.
10. The stadia hair readings for the staff station B are also observed and recorded.
11. The observations are closed on the first staff station A.
12. The theodolite is then set on the face left mode and the horizontal and vertical angles and the stadia hair reading are observed for both the staff station A and B are recorded by repeating the above procedure for the initial settings of 180°00’00” on vernier A. The staff stations are sighted in the same sequence as above but by swinging the theodolite to the left.
13. The average of the horizontal angles subtended by the line AB at the instrument station P and the vertical angles are found.
14. The average vertical angles and the staff intercepts are substituted in the relevant expression for horizontal distance for inclined line of sight and vertically held staff and the horizontal distances of the staff stations A and B from the instrument station P are determined by the principles of stadia tacheometry.
15. From the mean value of the horizontal angle APB and the horizontal distance PA and PB, the horizontal distance AB is determined by the cos rule.
16. The difference in elevation between the two staff stations A and B is also determined.
17. The gradient between the two staff stations A and B is determined from the difference in elevation and the horizontal distance between them. 

Inst At

Sighted To

Horizontal Circle Reading -Vernier

Included Angle

Average Included Angle

Vertical Circle Reading - Vernier

Average Vertical Angle

Stadia Hair Reading

A

B

Mean

C

D

Mean

Top

Middle

Bottom

P

APB

Angle A Angle B

 
The gradient between the two stations A and B is  1 in ____

1. The theodolite is mounted on the tripod stand.
2. The theodolite is centered over an arbitrarily selected station P from where the staff stations A and B can be sighted without any obstruction and the instrument is levelled using the foot screws.
3. The theodolite is set on the face right mode and the vernier A on the face right mode and the vernier A on the horizontal circle is initially set at 0°00’00” and the staff station A is sighted.
4. The central vertical cross hair is made to bisect the staff station A and the central horizontal cross hair is made tangential to 2.0 m mark on the staff station.
5. The horizontal and vertical angles are recorded by reading the horizontal and vertical circles respectively.
6. The stadia hair readings for the staff station A are also observed and recorded.
7. The theodolite is swing to the right and the staff station B is sighted.
8. The central vertical cross hair is made to bisect the staff station B and the central horizontal cross hair is made tangential to 2.0 m mark on the staff station B.
9. The horizontal and vertical angle are recorded by reading the horizontal and vertical circle respectively.
10. The stadia hair readings for the staff station B are also observed and recorded.
11. The observations are closed on the first staff station A.
12. The vernier A is then initially set  90°00’00” and the horizontal and vertical angles and the stadia hair readings are observed for both the staff stations A and B are recorded by repeating the above procedure.
13. The theodolite is then set on the face left mode and the horizontal and vertical angles and the stadia hair reading are observed for both the staff station A and B are recorded by repeating the above procedure for the initial settings of 180°00’00” and 270°00’00” on vernier A. The staff stations are sighted in the same sequence as above but by swinging the theodolite to the left.
14. The average of the horizontal angles subtended by the line AB at the instrument station P and the vertical angles are found.
15. The average vertical angles and the staff intercepts are substituted in the relevant expression for horizontal distance for inclined line of sight and vertically held staff and the horizontal distances of the staff stations A and B from the instrument station P are determined by the principles of stadia tacheometry.

16. From the mean value of the horizontal angle APB and the horizontal distance PA and PB, the horizontal distance AB is determined by the cos rule.
17. The difference in elevation between the two staff stations A and B is determined using the horizontal distance and the vertical angles in the relevant trignimetric expression. 

Inst At

Sighted To

Horizontal Circle Reading -Vernier

Included Angle

Average Included Angle

Vertical Circle Reading - Vernier

Average Vertical Angle

Stadia Hair Reading

A

B

Mean

C

D

Mean

Top

Middle

Bottom

P

APB

Angle A Angle B