levelling report-1

BQS MARCH INTAKE 2016 │FIELDWORK ONE │LEVELLING

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SCHOOL OF ARCHITECTURE, BUILDING AND DESIGN

BACHELOR OF QUANTITY SURVEYING (HONOURS)

SITE SURVEYING (QSB60103)

Fieldwork one: Levelling

Group member:

Name Student ID

1. Wong Qin Kai 0320024

2. Lee Shze Hwa 0320053

3. Ng Huoy Miin 0319097

4. Hoi Wei Han 0323335

Lecturer: Mr. Chai Voon Chiet

Submission date: 12th July 2016


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TABLE OF CONTENT

TITLE CONTENT PAGE NUMBER

1 Introduction to Leveling

1.1 Definition of Leveling

1.2 Definition of Terms Used in Leveling

1.3 Differential Leveling

1.4 Vertical Control Surveys

3-9

2 Outline of Apparatus

2.1 Automatic Level

2.2 Adjustable Leg-Tripod

2.3 Optical Plummet

2.4 Horizontal Bubble Level

2.5 Bar-Coded Level Rod

2.6 Plumb Bob

10-12

3 Objectives 13

4 Introduction to the site 13

5 Leveling Fieldwork

Field Data

5.1 Height of Collimation Method

14

6 Adjusted Data

6.1 Rise and Fall Method

15

7 Discussion 16

8 Conclusion 17

9 References 18


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1.0 INTRODUCTION TO LEVELLING

1.1 DEFINITION OF LEVELLING.

Levelling

Leveling is defined as “an art of determining the relative height of different points on, above or

below the surface”.

Principle of Levelling

The principle of levelling is to obtain horizontal line of sight with respect to which vertical

distances of the points above or below this line of sight are found.

The objective of Levelling

The objective of levelling is to find the elevation of given point with respect to some assumed

reference line called datum and to establish point at required elevation respect to datum.

1.2 DEFINITION OF TERMS USED IN LEVELLING

Level Surface

It is any surface parallel to the mean spheroidal surface of the earth. Since the earth is an oblate

spheroid, a level surface may be regarded as a curved surface, every point on which is equidistant

from the center of the earth.

Level line

It is a line lying in a level surface. It is therefore, normal to the plumb line at all points.


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Horizontal plane

A plane perpendicular to the local direction of gravity. In plane surveying, it is a plane

perpendicular to the local vertical line.

Horizontal Line

It is any line lying on the horizontal plane. It is usually a straight line tangential to the level line.

Vertical plane

It is a plane containing a vertical line.

Vertical line

It is a line normal to the level surface through that point e. g. a plumb line.

Vertical angle

Angle between two intersecting lines in a vertical plane, one of the two lines is commonly taken

as horizontal in surveying.

Datum

“It is an arbitrary level surface from which elevation of points may be referred”. In India mean sea

level is considered as datum of zero elevation it is situated at Karachi.

Mean Sea Level

It is the average height of sea for all stages of tides it is derived by averaging the hourly tide height

over a period of 19 years.


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Elevation or Reduced level

It is height or depth of any point above or below any datum. It is denoted as R.L.

Benchmark (B.M.)

It is a fixed reference point of known elevation with respect to datum.

Line of collimation

It is a line joining the intersection of cross hairs of diaphragm to the optical centre of object glass

and its continuation. It is also known as line of sight.

Height of instrument

It is the elevation of line of collimation with respect to datum.

Backsight (B.S.)

The first reading from a new instrument position.

Intermediate Sight (I.S.)

Readings between the backsight (B.S.) and foresight (F.S.)

Foresight (F.S.)

The last reading from an instrument position.


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Change Point (T.P)

It is a point on which both fore and back sight are taken.

There leveling has two type of layouts which are the rise and fall method and the height of

collimation method.

1.3 DIFFERENTIAL LEVELLING

DEFINITION OF DIFFERENTIAL LEVELING

The establishment of differences in elevation between two or more points with respect to a datum.

Normally surveyor will assign an elevation of 100.00 to the datum rather using the mean sea level

elevation.

THEORY

Add rod readings (BS) to benchmark or known turning point elevations to get the elevation of the

line of sight (HI). Subtract rod readings (FS) from the line of sight to establish elevations of

unknown points. Repeat over and over.


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SCHEMATIC

Elev + BS = HI

HI - FS = New Elevation

REDUCINGERRORS

Making certain the bubble is centered when you make a rod reading. Keeping the rod plumb when

the reading is taken. Establishing equal BS and FS reading distances. Equaling reading distances

will cancel out any error caused by the line of sight not being parallel with the axis of the bubble

tube on the Dumpy Level. Not as important with the self-leveling Automatic Levels. Lastly, it will

not always possible due to the terrain.

SUGGESTIONS FOR GOOD LEVELLING

Anchor tripod legs firmly. Checking of the bubble level before and after each reading. Taking as

little time as possible between BS and FS. Trying to keep the distance to the BS and the FS equal.

Providing the rod person with a level for the rod.

COMMONMISTAKES

Faulty reading of the rod. Not fully extending the rod for high readings. Touching the tripod during

reading. Confusion between recording BS and FS entries into the field book.


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CHECK

Page Checking. Method of checking arithmetic. The BS and FS columns are added up and their

difference should be equal to the difference between the beginning and ending elevations. Closure

Method of checking accuracy. The difference between the beginning and ending elevations for a

loop or the difference between the ending elevation and the known elevation of the ending BM.

1.4 VERTICAL CONTROL SURVEYS

A vertical control survey determines elevation with respect to sea level. These surveys are also

used as a benchmark upon which other surveys are based and high degree of accuracy is required.

These surveys are useful for tidal boundary surveys, route surveys, construction surveys and

topographic surveys. In a vertical control system, at least two permanent benchmarks should be

used, but more may be required depending upon the needs and complexity of the project. These

projects are needed for the construction of water and sewer systems, highways, bridges, drains,

and other major town or city infrastructure. These surveys can be done alone, but are often done

in conjunction with a horizontal control survey.

1.4.1 HEIGHT OF COLLIMATION METHOD:

It consists of finding the elevation of the plane of collimation (H.I.) for every set up of the

instrument, and then obtaining the reduced level of point with reference to the respective plane of

collimation.

1. Elevation of plane of collimation for the first set of the level determined by adding back side to

R.L. of B.M.

2. The R.L. of intermediate point and first change point are then obtained by starching the staff

reading taken on respective point (IS & FS) from the elation of the plane collimation. (H.I.)

3. When the instrument is shifted to the second position a new plane collimation is set up. The

elevation of this plane is obtained by adding B.S. taken on the C.P. From the second position of

the level to the R.L. C.P. The R.L. of successive point and second C.P. are found by subtract these

staff reading from the elevation of second plane of collimation Arithmetical check.


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Sum of B.S. – sum of F.S. = last R.L. – First R.L.

This method is simple and easy.

Reduction of levels is easy.

Visualization is not necessary regarding the nature of the ground.

There is no check for intermediate sight readings.

This method is generally used where more number of readings can be taken with less

number of change points for constructional work and profile leveling.

1.4.2 RISE AND FALL METHOD:

It consists of determining the difference of elevation between consecutive points by comparing

each point after the first that immediately preceding it. The difference between their staff reading

indicates a rise fall according to the staff reading at the point. The R.L is then found adding the

rise to, or subtracting the fall from the reduced level of preceding point. The arithmetic check in

this method is as follows:

∑ BS - ∑ FS = ∑ Rise - ∑ Fall = Last RL - First RL

This method is complicated and is not easy to carry out. Reduction of levels takes more time.

Visualization is necessary regarding the nature of the ground. Complete check is there for all

readings. This method is preferable for check levelling where number of change points are more.


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2.0 OUTLINE OF APPARATUS

2.1 AUTOMATIC LEVEL

An Auto level is a Professional Leveling Tool used by Contractors, Builders, Land Surveying

Professionals, or the Engineer who demands accurate leveling every time. Auto level set up fast

and easy to use and save time and money on every job.

1. Gun sight

2. Circular level (pond bubble)

3. Levelling Screw

4. Base Plate

5. Objective Lens

6. Focusing Knob

7. Horizontal fine motion screw

8. Horizontal circle window

9. Horizontal circle setting ring

10. Reticle adjusting screw cover

11. Eyepiece


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2.2 ADJUSTABLE-LEG TRIPOD

A tripod is a three-legged stand. Adjustable-leg tripods are the more common of the two in the

construction work especially outdoors because of generally uneven terrain. The adjustable-leg

tripod is easier to set up on uneven ground because each leg can be adjusted to exactly the height

needed to find level even on a very steep slope. The adjustable-leg tripod is also easy to transport

due to having retractable legs.

2.3 OPTICAL PLUMMET

In surveying, a device used in place of a plumb bob to center transits and theodolites over a given

point, preferred for its steadiness in strong winds.

2.4 HORIZONTAL BUBBLE LEVEL

Horizontal bubble is an instrument used to indicate the horizontal level. A slightly curved glass

tube which in incompletely filled with either spirit or alcohol.


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2.5 BAR-CODED LEVEL ROD

Bar-coded level rod can determine the relative height of the different points in the area under

survey.

2.6 PLUMB BOB

A plumb bob or a plummet is a weight usually with a pointed tip on the bottom, that is suspended

from a string and used as a vertical reference line.


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3.0 OBJECTIVES

1. To enhance students’ knowledge in leveling procedure.

2. To enable students to get hands-on experience in setting up and working with the auto-level.

3. To allow students to apply theories that had been taught in the classes in a hand-on situation

such as making adjustments for each reduced levels of every single staff station in order to

obtain the most accurate reduced levels.

4. To determine the error of misclosure in order to determine whether the levelling is acceptable.

4.0 INTRODUCTION TO THE SITE

We were asked to conduct a fieldwork by leveling around the staff parking of Taylor’s University

Lakeside Campus. The location of Benchmark (BM) was given with the reduce level of 100.00 m

at the lamp post labelled as BM 101. We were required to obtain the reduce level of the 10 locations

given as shown in the photo below.


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Field Data (Height of collimation method)

Back-sight Intermediate sight

Foresight Height of collimation

Reduce level Remarks

1.250 101.250 100.000 BM101

1.261 3.502 99.009 97.748 TP 1

1.175 97.834 TP 2

1.298 1.325 98.982 97.684 TP 3

1.385 1.320 99.047 97.662 TP 4

1.240 1.155 99.132 97.892 TP 5

1.245 1.285 99.092 97.847 TP 6

1.350 1.510 98.932 97.582 TP 7

1.245 1.150 99.027 97.782 TP 8

3.635 1.350 101.312 97.677 TP 9

1.320 1.300 101.332 100.012 TP 10

1.320 100.012 BM101

15.229 15.217 100.012

-15.217 -100.000

0.012 0.012

Error of distribution

= (100.012-100.000) /10

= (0.012) /10

= 0.0012


Foresight Height of collimation

Reduce level Adjustment Adjusted RL

Remarks

1.250 101.250 100.000 -0.000 100.000 BM101

1.261 3.502 99.009 97.748 -0.0012 97.746 TP 1

1.175 97.834 -0.0012 97.832 TP 2

1.298 1.325 98.982 97.684 -0.0024 97.682 TP 3

1.385 1.320 99.047 97.662 -0.0036 97.658 TP 4

1.240 1.155 99.132 97.892 -0.0048 97.887 TP 5

1.245 1.285 99.092 97.847 -0.0060 97.841 TP 6

1.350 1.510 98.932 97.582 -0.0072 97.578 TP 7

1.245 1.150 99.027 97.782 -0.0084 97.774 TP 8

3.635 1.350 101.312 97.677 -0.0096 97.667 TP 9

1.320 1.300 101.332 100.012 -0.0108 100.001 TP 10

1.320 100.012 -0.012 100.000 BM101

15.229 15.217 100.012

-15.217 -100.000

0.012 0.012

Arithmetical check:

B.S. - F.S. = Last R.L. - First R.L.

= 15.229 - 15.217 = 100.012 - 100.000

= 0.012


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Field Data (Rise and fall method)


Foresight Rise Fall Reduce level Remarks

1.250 100.000 BM101

1.261 3.502 2.252 97.748 TP 1

1.175 0.086 97.834 TP 2

1.298 1.325 0.150 97.684 TP 3

1.385 1.320 0.022 97.662 TP 4

1.240 1.155 0.230 97.892 TP 5

1.245 1.285 0.045 97.847 TP 6

1.350 1.510 0.265 97.582 TP 7

1.245 1.150 0.200 97.782 TP 8

3.635 1.350 0.105 97.677 TP 9

1.320 1.300 2.335 100.012 TP 10

1.320 0.000 100.012 BM101

15.229 15.217 2.851 2.839 100.012

-15.217 -2.839 -100.000

0.012 0.012 0.012

Error of distribution

= (100.012-100.000) /10

= (0.012) /10

= 0.0012


Foresight Rise Fall Height of collimation

Reduce level

Adjustment Adjusted RL

Remarks

1.250 101.250 100.000 -0.000 100.000 BM101

1.261 3.502 2.252 99.009 97.748 -0.0012 97.746 TP 1

1.175 0.086 97.834 -0.0012 97.832 TP 2

1.298 1.325 0.150 98.982 97.684 -0.0024 97.682 TP 3

1.385 1.320 0.022 99.047 97.662 -0.0036 97.658 TP 4

1.240 1.155 0.230 99.132 97.892 -0.0048 97.887 TP 5

1.245 1.285 0.045 99.092 97.847 -0.0060 97.841 TP 6

1.350 1.510 0.265 98.932 97.582 -0.0072 97.578 TP 7

1.245 1.150 0.200 99.027 97.782 -0.0084 97.774 TP 8

3.635 1.350 0.105 101.312 97.677 -0.0096 97.667 TP 9

1.320 1.300 2.335 101.332 100.012 -0.0108 100.001 TP 10

1.320 0.000 100.012 -0.012 100.000 BM101

15.229 15.217 2.851 2.839 100.012

-15.217 -2.839 -100.000

0.012 0.012 0.012

Arithmetical check:

B.S. - F.S. = Rise - Fall = Last R.L. - First R.L.

15.229 - 15.217 = 2.851 - 2.839 = 100.012 - 100.000

= 0.012


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7.0 DISCUSSION

In this leveling fieldwork, we were required to measure the reduced level of the 11 locations

given (including Benchmark) around the staff parking area at Taylor’s University Lakeside

Campus. Before start the fieldwork, we had learnt to set up the leveling instrument and the

precautions that we needed to be aware of to reduce the error. Benchmark (BM) has been given

with 100.00 m Reduce level (RL) at a lamp post labelled BM 101. After setup the instrument and

placed bar-coded level rod, the levelling process began by observed and recorded the backsight

(BS) at BM 1 and foresight (FS) at point A. The height of the instrument will remain the same for

each observation made until the instrument is moved to a new location. Then, we shifted the

location of the auto level and obtained BS of point A, intermediate sight (IS) of point B and FS of

point C. Since we could not obtain the reading of bar-coded level rod at point D, we were forced

to shift the auto level. The process was repeated by shifting the auto level in order to obtain the BS

and FS. At last, we were required went back to BM 1 and obtained FS to the calculate the error of

misclosure.

In order to check the accuracy of our leveling, we used the formula of 12√(k) which k is the

total number of setup to obtain the maximum allowable error of closure. Unfortunately, our first

obtained leveling data was not acceptable and we were forced to redo the leveling. We had decided

to have more setup to reduce the error and end up we had total 10 set up. The error of enclosure

which is 0.012 m is less than the maximum allowable error of closure which is 0.038 m. Hence,

our second leveling was acceptable.

We were decided to use both height of collimation method and rise and fall method to calculate

the RL of each point. Since the final RL is more than initial RL, the reduce level must be adjusted

by distribute the error against the number of setup. Therefore, the reduce level was adjusted by

subtracting to each set up. Lastly, we were required to arrange and convert the leveling data and

the adjusted the reduce level to computer in order to produce a fieldwork report.


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8.0 CONCLUSION

Throughout this fieldwork, we were appreciated to have this opportunity to learn the leveling

procedure and use the specialized site surveying apparatus. For example, automatic level,

adjustable-leg tripod, optical plummet, horizontal bubble level, bar-coded level rod and plump bob.

Besides, we also learnt the way to calculate the reduced level by using height of collimation

method and rise and fall method and also learnt to adjust the reduce level. Due to the first leveling

data was not acceptable, we had put more precaution on the leveling process to avoid error such

as ensure the instrument always in horizontal level by checking the bubble, double check the

reading that taken and ensure the plumb bob was perfectly centered over the peg.

It was a great experience for us to understand the scope of work of a site surveyor. A site

surveyor locates the buildings, roads and utilities for real estate develops and was responsible to

measure and mark their locations on the maps by using mathematics, specialized technology and

equipment.

As a future Quantity Surveyor, it helps us to know more about the site by comprehend the site

surveying knowledge. Overall, we were enjoyed the fieldwork and special thanks to our lecturer,

Mr. Chai by teaching us the how to conduct the fieldwork.


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9.0 REFERENCES

1.4.2 Rise and Fall Method

"How To Use Auto Levels". Newenglandlaser.com. N.p., 2016. Web. 4 July 2016. From

http://newenglandlaser.com/index.php?n=how_to_use_auto_levels

2.1 AUTOMATIC LEVEL

"Automatic Levels". EngineerSupply. N.p., 2016. Web. 4 July 2016.

From http://www.engineersupply.com/automatic-levels.aspx

2.2 ADJUSTABLE-LEG TRIPOD

"What Is A Tripod? How Do Tripods For Laser Levels Work? | How To Use Laser Level With

Tripod | Laser Levels | Johnson Level & Tool Mfg Company". Johnsonlevel.com. N.p., 2016. Web.

4 July 2016.

From http://www.johnsonlevel.com/News/WhatisaTripodHowdoTripods

2.3 OPTICAL PLUMMET

"What Is Optical Plummet? Definition And Meaning". Dictionaryofconstruction.com. N.p., 2016.

Web. 4 July 2016.

From http://www.dictionaryofconstruction.com/definition/optical-plummet.html

8. CONCLUSION

"What Is A Land Surveyor; Find Out What Surveying Is All About And What It's Like To Be In

The Surveying Industry | A Life Without Limits". Alifewithoutlimits.com.au. N.p., 2016. Web. 4

July 2016.

From http://www.alifewithoutlimits.com.au/about-surveying/

"What Are The Duties Of A Land Surveyor?". Work.chron.com. N.p., 2016. Web. 4 July 2016.

From http://work.chron.com/duties-land-surveyor-12939.html

http://newenglandlaser.com/index.php?n=how_to_use_auto_levels

http://www.johnsonlevel.com/News/WhatisaTripodHowdoTripods

http://www.alifewithoutlimits.com.au/about-surveying/

http://work.chron.com/duties-land-surveyor-12939.html

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