yield strength

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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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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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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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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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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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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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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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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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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http://goda02.com/survey-methodology-2/surveying-flow-chart


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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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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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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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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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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.

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TPBS

BS 1.35FS 1.41

3.22

Levelling Staff

BMA = 128.25

FS 3.02


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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

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BS TP

FS 1.41BS 1.35

3.22

FS 3.02

Levelling Staff

BMA = 128.25

131.47

RLC = 128.39


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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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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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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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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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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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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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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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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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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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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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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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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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