1. 1
BACHELOR OF QUANTITY SURVEYING (HONOURS)
QSB60103103946-M - SITE SURVEYING
Fieldwork Report 1
TITLE: LEVELING
Name Student ID
Yeo Dor Een 0316224
Welson Lum Wei Jiunn 0319514
Yap Jia En 0319550
Yong Sing Yew 0318766
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Table of Content
Content Pages
Cover Page 1
Table of Content 2
Introduction to Leveling 3-5
Introduction of Apparatus 6-11
Data and Results 12-14
Discussion 16
3. 3
INTRODUCTION TO LEVELING
Leveling may be part of determine the relative heights or elevation of points are object on the
earth’s surface. It deal with measurements in a vertical plane. It is also a level surface that
everywhere at right angles to the direction of gravity of the earth.
OBJECTIVES
The objectives of this field work 1 (Leveling) is to:
a) To give definitions as a basic for the proper understanding of leveling
b) To understand the methods used in leveling
c) To understand the collimation method and rise and fall method
There are few definitions of terms used in leveling which are:
DATUM
A datum may be a surface or a line to which observed heights are related. It is any arbitrarily
assumed level surface or line from which vertical distances are measured in India the datum
adopted for G.T.S. bench marks is the mean sea level at Karachi now in Pakistan. There are two
types of datum which are:
a) The ordnance datum (O.D) is the datum to which all heights shown on Ordnance Sydney
(O.S) maps are referred. The datum line is the mean sea level at Liverpool datum
b) Assumed datum is used where it is inconvenient or impossible to relate the work in hand
to the ordnance datum.
BENCH-MARK (B.M)
Bench-mark is a fixed point of know height above O.D from which the height above O.D of any
other point may be pointed. Bench-mark also used as our starting point and ending point during
our field work.
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REDUCED LEVEL
A reduced level is the height of a point or object stated with reference to the selected datum for
the work in hand. The reduced level can be increase or decrease at every points depends on the
datum. There are some formula to get the amount of reduce level which are:
a) The height of instrument - Back sight= Reduced level (Collimation method)
b) The previous height of instrument – (I.S) or (B.s)= Reduced level(Collimation Method)
For the rise and fall method is use the previous B.S to minus the I.S or F.S to get the amount
which will be negative or positive amount and add them with the reduced level of the previous
B.S.
LINE OF COLLIMATION
It is the line joining the intersection of cross hairs of the optical center of the object glass. The
line extending from an instrument along which distance objects are seen, when viewed with the
telescope. It also called the line of sight.
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BACKSIGHT
Back-sight is the first sight reading taken after the instrument has been set up. The sight taken to
a point whose height is known, has been assumed, or can be calculated. Its abbreviated is called
B.S and is taken at the start of the work at and a change point.
FORESGHT
Foresight also called the last staff reading denoting the shifting of the instrument. It is a termed
as minus sight. It is abbreviated to F.S and is taken a change point and at the end of operations.
INTERMEDIATE SIGHT
Intermediate sight is the sight or reading that take between the F.S and B.S. It is abbreviated to
I.S.
CHANGE POINT
It is appoint denoting the shifting of the level. It is after the reading of B.S and F.S where the
instrument is ready to move to a new position. It is abbreviated to C.P. A bench-mark may also
be taken as a changer point and it also called a turning point (T.P).
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Tripod Stand
It have 3 legs which can be extend to the height required. It function is to carry the Digital Level
and it has a special screw is done purposely to lock the Optical Plummet which attached to the
Digital Level.
Optical Plummet
A device which use to make sure the Digital Level is on the center position over a point.
8. 8
Way to set-up the Optical Plummet so that the Digital Level are at the center position
Rotate A and B at the same time and C at the different time to adjust the bubble move into the
center which mean the Digital Level is already in the center position. Do not rotate the three
rotate buttons at the same time.
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Pond Bubble
-When pond bubble is centered this mean the instrument’s standing axis is approximately
vertical.
-The compensators in the instrument take over and adjust the optical of Line of Collimation so
that it is horizontal.
-When the instrument is rotated the compensator ensure that a horizontal plane of collimation is
swept out.
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E-type leveling ruler
This type of ruler can allow us have a better vision on the reading compare to normal type ruler.
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COMMON ERROR SOURCES
There are always some common error sources due to the failure of the measurement. The
common error sources are:
a) Level rod not vertical
b) Levelling rod not fully extended or incorrect length
c) Level instrument not level
d) Instrument out of adjustment
e) Environment – wind and heat.
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Acceptable Error of closure = ±12 √k
K = the number of set-ups
±12 √11 = ±39.799mm
Hence, the leveling is acceptable.
Correctionper set-up
Error of misclosure ÷ Number of set up
= (100.0000-100.032) ÷ 11
= -0.003 m
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Discussion
For the first fieldwork, we were required to set up the leveling instrument on a
suitable spot. After finished set up, the height of instrument will remain the same
for each observation made until the instrument is moved to a new position. Two
persons carried their own level rods (vertical rods)stood at two different points and
mark the places with correction fluid. Then, the level rods’ readings were
measured and recorded. We were asked to measure 11 points (included bench-
mark) with 10 set ups in this fieldwork. After that, calculate the readings we
recorded in two methods which are height of collimation method and rise and fall
method and calculate the reduced level of each station. To ensure the total readings
are same or within the allowable error of closure, we use the formula of constant ×
√(distance).
constant× √(distance)
= ± 12 √k
= ± 12 √11
= ± 39.799mm
Therefore, the acceptable range for error of closure is ± 39.799mm. If the answer
is over ± 39.799mm, we have to do the fieldwork again until we get it. For our
group, we get the answer for the allowable error of closure, -0.032mm, thus it is
acceptable. After that, we need to do adjustment table for height of collimation
method and rise and fall method with this formula:
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Correctionper set-up
Error of misclosure ÷ Number of set up
= (100.0000-100.032) ÷ 11
= -0.003 m
Lastly, calculate the final reduced level with the addition of reduced level and
adjustment.
