Site surveying

procedures
and
applications in
construction
and the built
environment
Acknowledgement

I hereby take this opportunity to extend my sincere thanks to Mr. A.M.R.G. Athapattu who
is our lecturer for the subject of site surveying procedures and the knowledge that I gained
from this subject was a great help for me to complete this assignment.

Finally, I would like to thank my parents with family members and friends who was helped
and encouraged me to complete this assignment

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Table of content

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Table of figures

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Task 01

a.

Adjustment which are performed at each set up of level trial to the actual work of taking
observation called as temporary adjustment. Ones the instrument is permanently adjustment
than at each new position level is temporary adjustment in following operation to set axis of
rotation process is also known as setting temporary adjustment for dumpy level are,

1. Setting up level
2. Leveling of level
3. Focusing and elimination of parallax

Setting up level

In this operation first of all the level was taken out from box by holding in right hand and
dumpy level is fixed at the top of tripod by turning round only the leveling head with the left
hand. Length of tripod stand where spread in such a way so that level remains stable. Then the
level screws were bought in the center of their run and adjustment the height of instrument by
moving the length so that leveler or level man to take reading easily.

Leveling of level

Telescope was turn so that it should be paralleled to two legs pressed into the ground by third
leg. The longitudinal bubble was brought to the center approximately and at this stage third leg
was pressed into the ground. Accurate adjustment of level was done by moving telescope
parallel to any pair of foot screw and applying the rule right in and left out moved the foot
screw inward or outward and brought the bubble of longitudinal level in center than telescope
was removed 90o any clockwise manner so that it was exactly over the third foot screw. Here
the bubble was placed the center by its third foot screw by applying same rule.

Focusing and elimination of parallax

Apparent movement of image of an object with respect to cross hair when image from by object
glass does not fall in plane of deform is called as parallax. It was tested by moving the eye up
and down in case image fixed to cross-hair on movement of eye there is no parallax on the
other hand it image goes same direction as that of eye there is parallax which is removed by
focusing the eye piece of object tube a sheet of white paper present in front of object glass and
seen to eye piece and by adjusting the eye piece in handout in its sockets. The crosshair wear
made clear.

(Kharat, 2013)

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b.

There are six standard checks on a conventional theodolite and should be done on a regular
basis.

Plate bubble - Simply leveling the theodolite and freezing the bubble will check for plate
bubble error. If the bubble freezes away from the central position, the theodolite is
still leveled. Centralizing the bubble by adjusting the bubble tube is not a necessary
adjustment.

Verticality of crosshairs - With the instrument correctly leveled the vertical crosshair should
be truly vertical. To check this sight on to a well-defined distant object and move the
telescope up and down. The object should remain on the vertical crosshair throughout its
entire length.

Horizontal collimation - This check determines whether the optical axis of the telescope is
at right angles to the trunnion axis. With the theodolite set up and leveled sight a well-
defined mark, say 50 m away with the lower plate clamped. Record the horizontal plate
reading. Change face and sight on to the mark again. Record this plate reading. The
difference between the two readings should be 180 and any variation from 180 is twice the
collimation error. Collimation errors of 40 seconds or less are acceptable for most site
applications. This error will be eliminated by observing on both faces of the instrument.

Trunnion axis error - This check determines whether the trunnion (or horizontal) axis is at
right angles to the vertical axis. With the instrument set up and leveled, sight a high
target using the vertical crosshair (vertical angle approximately 40 50). Depress the
telescope and read a staff or other graduated scale laid horizontal under the target and facing
the theodolite. Change face and repeat this operation. If the two staff readings re within 5
mm the trunnion axis error is within 5 mm the trunnion axis error is within acceptable limits
for mot site applications. By observing on both faces of the instrument, this error will be
eliminated. However, this is quite impractical if the theodolite is used for plumbing purposes.

Vertical collimation error - The zero line of the vertical circle should be horizontal when
the altitude bubble is levelled or the automatic compensator is in operation. The check
follows the procedure for measuring vertical angles. The difference between the two reduced
vertical angles is twice the vertical collimation error. Collimation errors of 40 seconds or less
are acceptable for mot site applications. By observing on both faces of the instrument, this
error will be eliminated.

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Optical plummet - Set up and level the theodolite. Place on the ground a white card with a
cross, drawn on it. Position this card so that that the cross is exactly in the center of the
plummet gratitude. Tum the instrument through 180 and observe whether the cross remains in
the center of the circle.

c.

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Task 02

a.

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