Civil Engineering - Surveying - Discussion
Discussion Forum : Surveying - Section 2 (Q.No. 15)
15.
A dumpy level was set up at the midpoint between two pegs A and B, 50 m apart and the staff readings at A and B were 1.22 and 1.06. With the level set up a A, the readings at A and B were 1.55 and 1.37. The collimation error per 100 m length of sight is
Discussion:
20 comments Page 2 of 2.
R,D PRAJAPATI said:
7 years ago
THANKS @DOSS.
Nishant said:
7 years ago
Yes, your are right @DEEP.
Rohan said:
7 years ago
Thank you for the answer @DEEP.
(1)
Sunny said:
6 years ago
Yes, you are right, thanks @Deep.
Goutom saikia said:
6 years ago
True level difference get when the level set midway between A & B.
True level difference=1.22-1.06=.16 downward (Greater value give lower elevation so A is lower elevation than B).
And when an instrument set near to a point collimation error eliminate.So we get true reading for A.
True reading at A=1.55.
When instrument set near A then true reading at B=1.55-.16=1.39.
Error=1.37-1.39=-.02.
Error for 50 m=-0.02.
Error for 100 m=2*(-.02)=-0.04.
True level difference=1.22-1.06=.16 downward (Greater value give lower elevation so A is lower elevation than B).
And when an instrument set near to a point collimation error eliminate.So we get true reading for A.
True reading at A=1.55.
When instrument set near A then true reading at B=1.55-.16=1.39.
Error=1.37-1.39=-.02.
Error for 50 m=-0.02.
Error for 100 m=2*(-.02)=-0.04.
(17)
Abhijitth said:
5 years ago
Why are they not dividing by 2?
(ha-hb)-(ha'-hb')/2.
Isn't this the formula?
(ha-hb)-(ha'-hb')/2.
Isn't this the formula?
(1)
Ankit said:
4 years ago
Agree @Abhijeet,
why are they not dividing it by 2? Explain, please.
why are they not dividing it by 2? Explain, please.
(1)
Prince said:
4 years ago
@Abhijeet,
This is the formula to be used in reciprocal levelling. Here the staff is kept at the centre first so the true difference between the elevations is the actual difference between them.
This is the formula to be used in reciprocal levelling. Here the staff is kept at the centre first so the true difference between the elevations is the actual difference between them.
Stagir said:
4 years ago
Thank you @Goutam.
(1)
Karyeija Felex said:
4 years ago
@Ankit.
The 1st setting is a two peg test which eliminates error thus giving true difference in level.
We usually divide by two when the instrument is not at mid point so that errors on both BS and FS are eliminated.
The 1st setting is a two peg test which eliminates error thus giving true difference in level.
We usually divide by two when the instrument is not at mid point so that errors on both BS and FS are eliminated.
(2)
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