621. A relatively fixed point of known elevation above datum, is called
A. bench mark
B. datum point
C. reduced level
D. reference point.
622. The rise and fall method of reduction of levels, provides a check on
A. back sights
B. fore sights
C. intermediate sights
D. all of these.
623. The line of collimation method of reduction oflevels, does not provide a check on
A. intermediate sights
B. fore sights
C. back sights
D. reduced levels.
624. During levelling if back sight is more than foresight
A. The forward staff is at lower point
B. The back staff is at lower point
C. The difference in level, cannot be ascertained.
D. none of these.
625. The back staff reading on a B.M. of R.L. 500.000 m is 2.685 m. If foresight reading on a point is 1.345 m, the reduced level of the point, is
A. 502.685 m
B. 501.345 m
C. 501.340 m
D. 504.030 m
626. In reciprocal levelling, the error which is not completely eliminated, is due to
A. earth’s curvature
B. non-adjustment of line of collimation
C. refraction
D. non-adjustment of the bubble tube.
627. For true difference in elevations between two points A and B, the level must be set up
A. at any point between A and B
B. at the exact mid point of A and B
C. near the point A
D. near the point B.
628. While viewing through a level telescope and moving the eye slightly, a relative movement occurs between the image of the levelling staff and the cross hairs. The instrument is
A. covrectly focused
B. not correctly focused
C. said to have parallax
D. free from parallax.
629. Diaphragm of a surveying telescope is held inside
A. eye-piece
B. objective
C. telescope tube at its mid point
D. telescope at the end nearer the eye-piece
630. A dumpy level is set up with its eye-piece vertically over a peg A. The height from the top of peg A to the centre of the eye-piece is 1.540 m and the reading on peg B is 0.705 m. The level is then setup over B. The height of the eye-piece above peg B is 1.490 m and a reading on A is 2.195 m. The difference in level between A and B is
A. 2.900 m
B. 3.030 m
C. 0.770 m
D. 0.785 m
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