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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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DEFINITION OF TRAVERSE SURVEYING
A traverse survey is one in which the framework consists of a series of connected
lines, the lengths and direction of which are measured with the help of tape or chain
and an angle measuring instrument.
In other words, traverse survey consists of an interconnected series of lines, running
between a series of points on the ground called traverse stations. A traverse survey is
performed to measure both the distances between the stations and the angle between the
lines. Traverses have been used for local horizontal control over relatively small area or
for precise control over relatively large area.
When the lines from a circuit which ends at the starting point, the survey is
termed a closed traverse, if the circuit does not close, the traverse os known as open
one.The closed traverse is suitable for wide areas and for locating the boundaries of
the lakes,wood etc. ,where an open traverse is carried out in the of long strips of
country as in the case of canal, road , railway etc.
There are many different types of traverse:
Link traverse
Polygonal/Loop traverse
Open/Free traverse
Close traverse
Close travese is useful in marking the boundaries of wood or lakes . Open survey
is utilised in plotting a strip of land which can then be used to plan a route in road
construction.
Traverse networks have many advantages of other systems, including:
Less reconnaissance and organization needed
While in other systems, which may require the survey to be performed along a
rigid polygon shape, the traverse can change to any shape and thus can
accommodate a great deal of different terrains
Only a few observations need to be taken at each station, whereas in other
survey networks a great deal of angular and linear observations need to be
made and considered
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Traverse networks are free of the strength of figure considerations that happen
in triangular systems
Scale error does not add up as the traverse as performed. Azimuth swing
errors can also be reduced by increasing the distance between stations.
In total station traversing, total station is used for measurement of angles or tape
or chain, preferable, steel tape is used for linear measurement .This method is applied
for accurate and precise survey but for this fieldwork, we have to estimate our own
distance by using pegs.
Total station combines an EDM instrument, an electronic digital theodolite and a
computer in one unit. These devices automatically measure horizontal and vertical
angels, as well as distances and transmit the results in real time to a built-in computer.
The data can all be stored within the instrument or in an automatic data collector,
thereby eliminating manual recording. If the instrument is oriented in direction and
the coordinates of the occupied station are input to the system, the coordinates of any
point sighted can be immediately obtained. Total station instruments can accomplish
all surveying tasks including topographic, hydrographic, construction surveys and
cadastral mush more efficiently than transits and theodolites. In addition the can also
measure distances accurately and quickly.
These devices can automatically measure horizontal and vertical angles, as well as
slope distance from a single setup. From the data they can instantaneously compute
horizontal and vertical distance compoenents, elevations and coordinates of points
sighted and display the results on a liquid crystal display (LCD).
All total stations have the same common feature, which are as follows:
Horizontal tangent screw
o The clamp ensures that when engaged the horizontal circle is fixed.
Horizontal motion clamp
o The slow motion screw allow for the movement of the instrument
around the horizontal axis.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Optical plummet telescope
o The optical plummet allows the instrument to be precisely centered
over the station. The line of sight through the optical plummet is
exactly the same as the vertical axis of the total station
DEFINITION OF LEVELING
Leveling is the operation required in the determination or more strictly, the
comparison, of heights of points on the surface of the earth. The qualification is
necessary because the height of one point can be given only relative to another point
or place. Leveling is also the name given to the process of measuring the difference in
elevation between two or more points. It deals with measurements on a vertical plane.
The elevation of a particular point is the vertical distance aboce or below a reference
level surface (normally sea level) to the point in question. In surveying, the reference
datum that is any arbitrary surface to which the observed height of points are
referred. The Mean Sea Level (MSL) affords a convenient datum the world over and
elevations are commonly given as so much above or below sea level.
There are two main instruments used in levelling. There are:
LEVEL
o Level consists of four parts which are the telescope, level tube,
levelling head and the tripod. Each of the parts of level has its own
purpose. Telescope is used to provide the line of sight while level tube
is used to make the line sight horizontal. On the other hand, the
levelling head which is also known as tribach and trivel stage provides
the case to bring bubble in its sentre of run. Meanwhile, tripod is used
to suppport the instrument (telescope, level tube, levelling head).
o There are few types on level used in fieldwork. For instance dumpy
level, wye level, tilting level and automatic level. In this laboratory,
we have identified that the type of level we were using was automatic
level.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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o The automatic level employs a gravity-refereced prism or mirror
compensator to orient the line of sight (line of collimation)
automatically. The instrument is quickly leveled when a circular spirit
level is used. When the bubble has been centered (or nearly so), the
compensator takes over and maintains a horizontal line of sight, even
if the telescope is slightly tilted. Automatic levels are easy to set up
and use, and can be obtained for use at almost any required precision.
Levelling Staff
o Levelling staff are manufactured from wood, metal or fiberglass and
are graduated in feet or meters. The foot root canbe read directly to
0.01 ft, whereas the metric cod can usually be read directly only to
0.01m, with millimeters being estimated. Metric rod readings are
normally booked to the closest 1/3 cm, or ½ cm (0.000, 0.003, 0.005,
0.007, and 0.010); more precise values can be obtained by using
optical micrometer. One-piece rods are used to more precise work. The
most precise work requires the face of the rod to be invar strip held in
a place under temperature-compensating spring tension (invar is a
metal that has a very low rate to thermal expansion).
o Most levelling surveys utilize two- or three-peive rods graduated in
either feet or meters, the sole of the rod is a metal plate that can
withstand the constant wear and tear of levelling. The zero mark is at
the bottom of the metal plate. The rods are graduated in a wide variety
of patterns, all of which readily respond to logical analysis.
o There are two types of levelling staff, which are self-reading and target
staff. Self-reading staff can be divided into 3 categories, which are
solid staff, folding staff and telescopic staff. In this laboratory, we
were using the telescopic staff (sop with pattern). When fully
extended, it is usually 14 ft (5 m) in length. The usit used is
centimeters (cm).
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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METHODOLOGY OF TRAVERSING
PROCEDURE
1. Surrounding of proposed site was chosen as a scope of study or proposed site.
2. A number of control points (CP) were established at the proposed site. (peg 1, peg
2, peg 3, etc).
3. The total station was plumbed over peg 2 and accurately leveled. Prisms were
plumbed over peg 1 and 3.
4. Peg 1 were sighted on face left with theodolite set to the required horizontal
angle. The reading was entered in the field book.
5. Peg 3 were sighted and the horizontal angle was taken.
6. The instrument was set to face right (by transiting the telescope) and peg 1 was
sighted again.
7. Peg 3 was sighted and the reading was taken.
8. Distance was measured by collimating the center of prism at peg 1. The reading
was taken and entered in the field book. Distance between peg 2 and 3 also done
with the same technique.
9. The total station was moved to peg 3. Prisms were plumbed over peg 2 and 4. Peg
2 was sighted on face left with theodolite set to the reading taken from step 7
above.
10. Peg 2 was sighted and the horizontal angle was taken. The instrument was set to
face right and peg 4 was sighted again. Then peg 2 was sighted and the reading
was taken.
11. Distance was measured the same way for both peg by repeating step 8.
12. Step 9-11 was repeated on peg 3 until the total station back to peg 1. All readings
were observed and recorded.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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The method of measuring the angle and bearing of a traverse may be divided into
classes:
a) Those in which the angle at different stations are measured directly and the bearing
subsequently calculated from the measured angles and the given bearing of an initial
line
b) By direct observation of bearing of different survey lines by a total station.
A) Total Station Traversing by Direct Observation of Angle:- In this method,
horizontal angles measured at different stations may be either,
i. Included Angle, or
ii. Defection Angle
1) Traversing by the method of included angles:-
In a closed traverse included angles can be measured by running a traverse in
clockwise or counterclockwise direction. The common practice is to run a closed
traverse in counterclockwise direction, but it is well to adhere to a regular of routine
of measuring angles. Generally interior angles are obtained it the traverse is run
anticlockwise and exterior ones when it is run clockwise as shown in the figure 3.1.
Figure 3.1
The angle may be measured by the repetition method and the observation should be
taken with both the faces and also by reading both the verniers. Then averaging the
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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value of each angle should be calculated. It will ensure desired degree of accuracy
and removal of most of the instrumental errors.
2) Traversing by the method of deflection angle:-
This method of traversing is more suitable in surveys for railway, roads, pipeline etc.
in which a series of traverse lines may make small deflection angles with each other.
In measuring deflection angles having observed the bearing at the starting station ‘L’
Set the theodolite at each of station such as M,N,O,Q. Bisect the back stations using
lower clamp and its tangent screw. The vernier may be set to zero or the initial
reading may be taken. The theodolite is transited and the forward station is bisected
with upper clamp screw and the tangent screw. The verniers are again read, the
difference between the first set of reading and the second gives the angle of defection.
The measurement is either right or left handed and this direction must be most
carefully noted in the field book. Chaining is done in the usual manner.
Figure 3.2 Deflection Angle Method
Traverse Survey
At the commencement of contract all the basic traverse points will be checked with
engineer and if any are found to be missing or appear to have been disturbed,
necessary arrangements will be made to re-establish the points and traverse survey is
carried out and if any adjustments would be found which would be done with the
Engineer. Subsequently control point coordinates would be submitted to the Engineer
for approval.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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TBM Survey
Initially the Engineer’s/Employer’s occurrence will be sought to obtain details of
permanent bench marks tied with national grid. Temporary bench marks will be
established at the rate of four per km and also at or near all structures and TBM list
and levels would be submitted to the Engineer for the approval. Checks would be
carried out on these bench marks once every month and adjustments, if any should be
agreed with the Engineer. An up-to-date record of all bench marks including
approved adjustments would be maintained with the Engineer.
Center Line Setting out and Marking
Using total stations and approved coordinates of control points, the road center line
would be marking at every 10m interval on the road jointly with the Engineer.
Chainage would be marked on the road center line in each 20m and 100m interval
with meter and kilometer interval respectively. With the aid of rope and road marking
paint, the center point marked in every 10m intervals of the road would be extended
as a center line and that established centerline would be maintained until the end of
the project.
Correction
According to the Engineer’s instructions, corrections if any would be made and which
would be followed for the remaining work.
Cross Section Survey
The cross section survey would be commenced as soon as center line is marked and
approved by the Engineer. Levels of the cross section will be taken at every chainage
point marked on the center line. Cross sections at 20m intervals and in special cases
such as sharp curves; the cross section intervals reduced to 10 meters will be
submitted to the Engineer’s approval. At the same time, for plotting of longitudinal
section (LS) the center value of each cross section would be used.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Submission of Drawings
Initial cross section drawings plotted on A4 sheet on scale of 1:1000 both vertical-
horizontal and longitudinal profiles of the road (both hard & soft copy) would be
submitted to the Engineer along with back up data sheets for approval.
Flow Chart
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Calibration
(a) Level Instrument
Calibration certificate for brand new level instrument is given by the
manufacturer and two peg level tests on the leveling instrument would be
carried out once in a month and if we would find any error in instrument
during working, immediately we would be attending to the calibration of the
instrument.
(b) Total Station
Calibration certificate for brand new total station is given by the manufacturer
and once in an every six month period, the calibration would be carried out
until the project end accordance with relevant standards and if we would find
any defect in instrument during working, immediately we would be attending
to the calibration of the instrument.
METHOD OF EXECUTING THE FIELDWORK:
Temporary adjustment of total station should be made at every instrument
setting and preparatory observation with instrument. The temporary adjustments
include:
i. Setting up of the instrument
Assuming that the total station is to be erected over a ground mark which is a
peg driven into the ground. A nail driven into the top of the peg defines the
exact position for centering, which may referred to as station X. The
equipment must be centred all the time over the station mark X by using a
plum bob by adjusting legs. It is also important to adjust the small circular
bubble so that it is centred by using eye judgement.
ii. Levelling up
After having centred and approximately levelled the instrument, accurate
leveling is done by adjusting the foot screws to move the optical plummet
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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cross-hair with the reference to the plate level. It is important in order to make
the vertical axis exactly vertical.
iii. Eliminating Parallax
Parallax is a condition happen when the image formed by the objective is not
in the plane of the cross-hairs. Parallax should be eliminated in order to have
accurate sighting. There are two ways to overcome or eliminate the parallax.
There are by accurately focusing the cross-hairs against a light background
and focusing the instrument on a distant target or by focusing the eye-piece
for distinct vision of the cross hairs.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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METHODOLOGY OF LEVELING
PROCEDURE
1. Proposed site was slected as scope of study.
2. First Staff was sited on the TBM.
3. The level was set up at position I1, having a constant distance from TBM.
4. For the first staff, the reading was recorded as back sight, the foot of the staff
being held on the TBM and the staff held vertically.
5. The reading of other staff positioned were noted as intermediate sight until the
last point where instruments was then shifted to another point. This point is
known as change point.
6. The staff was moved to C (change point) and reading taken and noted as
foresight.
7. While the staff remains at C, the instrument was then shifted to next point with
intervals of same distance to another position, I2. A reading was taken from the
new position to the staff at C and noted as backsight (BS).
8. The staff was moved to D (intermediate sight) and reading taken.
9. The staff was moved to E being another change point and reading taken.
10. The instrument was shifted to I3 and a new reading was taken from the new
position to the staff at E.
11. Step 9 and 10 were repeated until the final staff position was back to the first
point and create closed transverse.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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There are few methods of executing the fieldwork, which are flying level,
longitudinal and cross-section levelling and check levelling. Flying level is a process
of ordinary spirit levelling on a route for the purpose of determining differences in
elevation, i.e direct differential levelling. It is quick but approximate method of
levelling. Long distances are taken as sights. It is also consists only of Back Sight and
Fore Sight and it is used for reconnaissance of an area or for approximate checking of
levels (to check the accuracy of work). Longitudinal sectioning, which is also known
as profile levelling is a process of determining the height of points across a measured
distance of intervals along a fixed line. This fixed line may be of straight, a
succession of straight line or a series of straight line corrected by curved line. The
main purpose of profile levelling is to enable engineers to relate the relationship
between ground surface existed in the scope of study and the levels of proposed
construction site. Meanwhile, cross sectioning refers to a drawing which is drawn
perpendicular to the centreline of the site. This drawing shows the profile view of the
ground cross-section drawing is significance in estimating the volume of earthwork
needed to construct a roadway, railway, etc. Check levelling is the operation of
running levels for the purpose of checking the series of levels, which have been
previously fixed. At the end of each day’s work, a line of level is run, returning to the
starting point of that day with a view to check the work done on that day.
The are two methods in calculating the reduced level (RL) of point which are
set up at a measured interval of fixed line. There are:
RISE AND FALL METHOD
HEIGHT OF COLLIMATION METHOD
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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RISE AND FALL METHOD
The rise and fall method consists of determining the difference of level
between consecutive points by comparing each point after the first with that
immediately preceding it. The difference between their staff readings indicates a rise
or fall according as the staff reading at the point is smaller or greater than that at the
preceding point. The Reduce Level (RL) of each point is then found by adding rise or
subtracting fall to or from the RL of the preceding point. This method provides a
complete check on intermediate RL in addition to BS and FS. This method is used for
differential leveling and other precise leveling operation
CONCEPT OF RISE AND FALL METHOD
Reduced level at A = BMA + BS Reading on staff – FS Reading on staff
= 128.25 + 3.22 – 1.41
= 130.06 m above datum (rising level)
Therefore, difference in height A to B (BS – FS) = 128.25 – 130.06 = -1.81m
The levels are known as Reduced Level (RL) as they refer to a datum level and thus
giving the reduced level of land at these points.
14
TPBS
BS 1.35FS 1.41
3.22
Levelling Staff
BMA = 128.25
FS 3.02
KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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HEIGHT OF COLLIMATION METHOD (HCL)
The collimation method consist of finding the elevation of the plane of
collimation for easy set-up of the instrument and then obtaining the Reduce Level of
points with reference to the respective plane of collimation. For an arithmetic check,
the difference between and sum of the Back Sight (BS) and the sum of the Foresight
(FS) should be equal to the difference between the first and last RL. The collimation
method is generally used in profile leveling and in settingout levels for constructional
work.
Height of Collimation = BMA + BS Reading on Staff A
= 128.25 + 3.22
= 131.47m above datum
RLB = Height of Collimation – FS reading on staff A
= 131.47 – 1.41
= 130.06m above datum
15
BS TP
FS 1.41BS 1.35
3.22
FS 3.02
Levelling Staff
BMA = 128.25
131.47
RLC = 128.39
KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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COMPARISONS BETWEEN THESE TWO METHODS
There are pros and cons between these two methods. HCL method is more
rapid and less tedious compared to Rise and fall method. However, mistakes in the
level pass of the points are sometimes not taken into account. Rise and fall method is
often used where there are a great number of intermediate sights levelling. On the
other hand, if a many reading are taken from every instrument position, HCL is a very
good method to be used when setting out level.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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WORK PROCESSES FOR TRAVERSE SURVEY AND LEVELING:
Work processes of the traverse and leveling has few steps that need to be taken care
of. Below is step-by-step pseudo code for work processes for both traverse survey
and leveling:
1. To start leveling, we must first determine the temporary bench mark for it. In
order to determine the TBM, we are using GPS / GIS to determine the
selected TBM. In Siar Beach Resort, we chose a trunk to be our TBM.
2. Then we are ask to find our first point, which is later to be pegged on. This is
important as we are using a same point or peg for our traverse survey after we
completed our leveling.
3. After that, we set our level, which is an automatic level a temporary
adjustment. Temporary adjustment or station adjustments are those which are
made at every instrument setting and preparatory to taking observations with
the instrument. It consist of the following:
a. Setting up the level
The operation of setting up includes fixing the instrument on the tripod
and leveling the instrument approximately by leg adjustment. The
purpose of setting up is to adjust the instrument to a convenient height
and with the tribrach approximately horizontal
b. Leveling
This is done with the help of three-foot screws to center the bubbles,
with reference to the plate levels. The purpose of leveling is to make
the vertical axis truly vertical.
c. Elimination of parallax
Parallax is a condition that arises when the image formed by the
objective is not in the plane of the cross-hairs. Parallax can be
eliminated with two steps: by focusing the eye-piece for distinct vision
of the cross-hairs and by focusing the objective to bring the image of
the object in the plane of cross-hairs.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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4. Note that the level must be approximately set in the middle of two points. This
is to make the smooth the work flow as the distance is approximately constant.
5. Since we are using peg instead of any type of tape measurements, hence we
have to use other alternative to find the distance between two points. Thiscan
be done by reading the staff reading on the top cross-hair of level and the
lower cross-hair of level. By obtaining the difference between this two point,
we multiply by 100 to get the approximate distance between level and each of
the staff (Back Sight and Fore Sight).
6. By following the procedure written in the methodology, the leveling fieldwork
can be done with the accuracy of 3rd class order.
7. After completed with our leveling, we start with our traversing by choosing 10
pegs to complete it. This is because it the the least number that we can do to
complete the traverse as most of them are on the critical point. To start the
traverse, we are asked to set a temporary adjustment on second peg.
Temporary adjustment of total station should be made at every instrument
setting and preparatory observation with instrument. The temporary
adjustments include:
i. Setting up of the instrument
Assuming that the total station is to be erected over a ground mark
which is a peg driven into the ground. A nail driven into the top of the
peg defines the exact position for centering, which may referred to as
station X. The equipment must be centred all the time over the station
mark X by using a plum bob by adjusting legs. It is also important to
adjust the small circular bubble so that it is centred by using eye
judgement.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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ii. Levelling up
After having centred and approximately levelled the instrument,
accurate leveling is done by adjusting the foot screws to move the
optical plummet cross-hair with the reference to the plate level. It is
important in order to make the vertical axis exactly vertical.
iii. Eliminating Parallax
Parallax is a condition happen when the image formed by the objective
is not in the sighting. There are two ways to overcome or eliminate
the parallax. There are by accurately focusing the cross-hairs against a
light background and focusing the instrument on a distant target or by
focusing the eye-piece for distinct vision of the cross hairs.
8. The completion of traverse survey is said to be done when the the prism is set
on the first point where we set our total station, which is in Siar Beach
Resort’s case, on second peg.
9. Then, we did a discussion on both fieldwork at night. If the value of
misclosure is more than the limit of the class order that has been set by Sir
Ron Aldrino (Traversing) Chan and Sir Larry (Leveling). If the value is more
than the class order, hence we need to repeat all the procedure all over again.
If it didnt, in our case, then we proceed with sketching and draw the survey
plan.
10. The report was sent 2 days after the camping survey.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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DISCUSSION : TRAVERSE SURVEYING:
First, we need to get the last mean and the first datum (which is usually a face
left). For example, the last mean obtained is not the same as the bearing of the face
left, which are 124°29’15” and 304°30’00” respectively. Since the bearing of the face
left is normally taken as datum, the bearing of the face right is corrected as
124°30’00”. The misclosure of the traverse can be obtained from the following
formula:
Misclosure = Last of mean – Datum
Hence, in this situation, we have calculated and found out that the misclosure for this
traverse is 0°0’15”. Since the last mean obtained is smaller than the bearing of the
datum, the misclosure is now become positive. This shows that the last mean has to
be added by certain degree of correction in order to get the same bearing as datum. In
order to obtain the correction for each station, it can be obtained by multiplying the
setup number with the value of misclosure and divided by the total number of station.
This can be proven by following formula :
Correction=(setup number xmisclosure)totalno .of setu p
Errors are said to be unavoidable. Hence, correction is needed to corrected any error
that commonly caused by the instruments. Furthermore, the correction has to be done
due to misclosure of the traverse. If we refer to the recorded mean and the datum, it
does not meet at the same bearing
After all the bearings have been corrected, those bearing will be used to draw
or sketch the area and diagram of the traverse. From this diagram, the included angles
are calculated based on the bearings of the lines of the traverse and also be referring
to the drawn diagram. From the diagram have been drawn, the shape of the traverse is
triangle. The total included angle of any polygon is calculated based on the formula:
Total included angle = (2n – 4)90°
where n is the number of side, which is refers to number of station for this case
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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For the polygon, the total included angle that is obtained from the above
formula. By adding all the include angle of our traverse based on the bearings of the
lines of traverse and the diagram, both of them must resulting a value , for example
1440°00’00”. This shows that our included angle are valid and this prove that our
traverse has been corrected correctly.
Then, we are executing the linear measurement and partial coordinates. This
can be done by summing the positive and negative partial coordinates for both
northing and easting (latitude N and departure E). The algebraic sum should be zero
in both cases as the traverse finished at the same point at which it started. For this
fieldwork, we are using Compass (Bowditch’s) Method as it is one of the easiest
method in order to determine the partial coordinates. We calculated both latitude and
departure based on the following formula:
∆ N=lcos θ
Where ∆ N=latitude
l=lengthof line
θ=bearing of line
and
∆ N=lsin θ
Where ∆ N=latitude
l=lengthof line
θ=bearing of line
Let say that we obtained 0.111 and 0.037 for our latitude and departure. This
misclosure can be obtained by summing up all the positive and negative partial
coordinates for both northing and easting (latitude N and departure E).The accuracy
of the usual traverse with a 1-minute transit is about 1:30000(at 1st survey order)
Therefore this value is still acceptable. The correction was made for both latitude and
departure by using a given formula (Compass rule) :
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Correction=C lΣl
Where C=∑ of latitudes∨departuresmisclosurewith signchange
Σl=perimeterof traverse
l=length of the particular course
By using this formula, we are able to adjust the latitudes and departures to ensure that
the sums of latitudes and departures equal to zero. Let take for example, during our
camping at Siar Beach Resort, our latitude is set at 1°44’54.450” N while our
departure is 109°52’35.868” E. After doing all the calculation, we found out that the
latitude and departure back to 1°44’54.450” N and 109°52’35.868” E respectively.
Hence, this shows that our calculation that we made is correct.
Error is said as unavoidable while doing total station fieldwork. This error can
be calculated as follow:
Misclosure = Last of mean – Datum
Let says that we have the situation where on the first attempt of executing traverse
survey, we failed to get the required accuracy. This is because we obtained a
misclosure which is more than the limit misclosure of required class order. This may
is due to unavoidable circumstance, e.g the total station that we used is broken
(there’s a problem arise when we’re trying to calibrate the optical plummet
telescope). Hence due to this, we have to re-do this fieldwork all over again.
There are several factors contributing to this error that may arise during
measuring traverse angle, which are:
Inaccurate centering of the total station or signal
Non-verticality of the signal
Parallax not eliminated or improper focusing of telescope
Lateral refraction, wind and atmospheric effects
Inaccurate bisection of the signal
Total station not level and not in adjustment
Incorrect use of the total station
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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Mistakes in reading and booking
During executing this fieldwork, we identified that the following factors are
mainly contributing to this error, which are:
Inaccurate centering of the total station or signal
o The centering may not inaccurate, but we did our best to get it as
accurate as possible.
Total station may not level and not in adjustment
o During the experiment, we have to level and centering the total station
at the same time. Since the centering may not inaccurate, there’s a
possibility that total station may not level but as far as our concerned it
is leveled and centered.
Parallax not eliminated or improper focusing of telescope
o There may be parallax error exist while focusing the telescope to the
prism.
During our experiment was commenced, the weather is rainy. This may affect
our result as the soil is damp and the peg may move a little bit to right or left.
Some of the pegs are missing as it may get hit by the car and we have to
estimate the last point where the pegs are located.
Prism may not level and not in adjustment
o During the experiment, we have to level and centering the prism at the
same time. Since the centering may not accurate, there’s a possibility
that prism may not level though as far as our concerned it is leveled
and centered.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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DISCUSSION: LEVELING
Error is said as unavoidable while doing leveling fieldwork. This error can be
calculated as follow:
error=1 st readingof Reduce Level−Last read ingof reduce levelno .of set up
After the value of error is obtained, correction is made. There are several factors
contributing to these factors:
Common Error
o Wrong booking
o Wrong staff reading
o Wrong cross-hair stadia used to read staff
o Spirit level not centered
o Omission or wrong entry on booking sheet
Constant Error
o Non-vertical staff
o Collimation error of instrument
o Staff graduation errors
Random Error /Accidental
o Human Error – eyesight peculiarities
o Weather – strong wind
o Movement of the turning point or change point
During executing the laboratory, we identified that the following factors are
mainly contributing to this error, which are:
Non-vertical staff
o When the staff is not vertically held, the reading taken will not be
accurate.
Human Error – eyesight peculiarities
Measurement of distance is inaccurate
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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o We were using line tape to measure distance from one point to another
point, which was highly affected by dampness of the soil. This factor
influenced our readings more since some of the soil was wet and the
tape may shrink making the measurement of distance no longer
accurate. Besides that it is really hard to straighten the tape. Hence,
this will contribute to inaccuracy of the distance.
Spirit Level of vertical staff (error in instrument)
o One of the spirit level of vertical staff is unable to be centered. This is
because the instrument is broken.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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CONCLUSION:
From what I have learn this whole semester, A traverse survey consists of an
interconnected series of lines, running between a series of points on the ground called
traverse stations. A traverse survey is performed to measure both the distances between
the stations and the angle between the lines. Traverses have been used for local horizontal
control over relatively small area or for precise control over relatively large area.
Leveling is the operation required in the determination or more strictly, the
comparison, of heights of points on the surface of the earth. The qualification is
necessary because the height of one point can be given only relative to another point
or place. Leveling is also the name given to the process of measuring the difference in
elevation between two or more points. It deals with measurements on a vertical plane.
The elevation of a particular point is the vertical distance aboce or below a reference
level surface (normally sea level) to the point in question. In surveying, the reference
datum that is any arbitrary surface to which the observed height of points are
referred. The Mean Sea Level (MSL) affords a convenient datum the world over and
elevations are commonly given as so much above or below sea level.
During our camping at Siar Beach Resort, we have come up with the results
obtained from the fieldwork executed using the method of traversing for a closed
traverse. Although there’s misclosure, the correction had been made to this data. It is
shown that these values calculated are valid since they converge with the theoretical
value given. For example, the total included angle in a polygon and the total included
angle of our polygon is must be the same. Hence, this shows that our included angle
are valid and this prove that our traverse has been corrected correctly. For our
booking on linear measurement and partial coordinates, we obtained a misclosure for
both of our latitude and departure. Since the accuracy of the usual traverse with a 1-
minute transit is about 1:30000(at 1st survey order), therefore this value is still
acceptable. Errors are commonly found in traverse survey. By taking several
precautions (make sure that total station leveled and adjusted, accurately centering of
the total station or signal, no parallax error by using proper focusing of telescope)
should be taken in order to reduce the error.
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KNS 1461 Civil Engineering Laboratory 2 Faculty of Engineering Universiti Malaysia Sarawak
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From backsight and foresight readings, variations of reduce level are obtained.
This shows that the level of each point is not as flat ground as seen by naked eyes.
There’s misclosure while during the leveling, which can be corrected by using
formula given. The accuracy must be not less than 3rd Class Order. The accuracy can
be obtained and calculated by using following formula:
C=12√K Where C = correction
K = distance in kilometres
Error is commonly found in leveling. Despite of that fact, precautions e.g
make sure that the staff is vertically held, make sure a proper adjustment of
instrument is made and using metal tape should be taken in order to reduce the error.
REFERENCES
Books
2009, Hasbullah M.A., Openg I., Simplified Land Surveying, Arah
Publichations
2005, Dr. Punmia B.C., Jain A.K., Jain A.K, Surveying Vol. 1, Laxmi
Publications (P) Ltd
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