SCHOOL OF ARCHITECTURE, BUILDING AND DESIGN

BACHELOR OF QUANTITY SURVEYING (HONOURS)QSB60103103946-M Site Surveying

Fieldwork Report 1LEVELLING

GROUP MEMBERS STUDENT ID

Liew Li Wen 0324297

Lim Kar Yan 0325602

Tan Hwee Min 0326057

Esther Chuah Ning Sie 0321422

TABLE OF CONTENT

Content Pages

Cover Page 1

Table of Content 2

Introduction 3 - 7

Objectives 8

Data and Results 9 - 13

Discussion 14 - 15

1.0 INTRODUCTION

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1.1 Introduction to levelling

Image source:sgf.rgo.ac.uk

Levelling is the general term applied to any various process by which elevations of points or

differences in elevation is determined.Levelling is the measurement of geodetic height using

an optical levelling instrument and a level staff or rod having a numbered scale. The

objectives of levelling is to find the elevation of a given point with respect to some assumed

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

Purpose of levelling:

● Levelling provides data for determining the shape of the ground and drawing

topographic maps.

● The elevations of new facilities such as roads,structural foundations,and pipelines

can then be designed.

● The designed facilities are laid out and marked in the field by the construction

surveyor.

● Determine the proper slope of a road,the first floor elevation of a building,the required

cutoff elevation for foundation piles,the invert elevation for a storm sewer and etc.

1.2 Term used in levelling

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Elevation: The vertical distance of a point above or below given reference surface is called

the elevation of point.

Level Surface:A level surface is defined as a curved surface which at each point is

perpendicular to the direction of gravity at the point. The surface of a still water is a truly level

surface. Any surface parallel to the mean spheroidal surface of the earth is, therefore, a level

surface.

Datum:Datum is any surface to which elevation are referred. The mean sea level affords a

convenient datum world over, and elevations are commonly given as so much above or below

sea level. It is often more convenient, however, to assume some other datum, specially, if only

the relative elevation of points are required.

Bench-mark(B.M.): It is a relatively permanent point of reference whose elevation with respect

to some assumed datum is known. It is used either as a starting point for levelling or as a point

upon which to close as a check.

Temporary bench-mark (T.B.M)is a marking, or location, with a known elevation. These

markings are not usually permanent. They are used by a person doing leveling work as

intermediary points when carrying a known elevation from one point to another

Reduced level(R.L.): A reduced level is the vertical distance between a survey point and the

adopted level datum.

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Image source:www.fao.org

Back-sight(B.S.): Back-sight is the first sight,or reading,taken after the instrument (the

level)has been set up.

Foresight(F.S.): Foresight is the last staff reading taken before changing the instrument to the

other position.

Intermediate sight( I.S.):An intermediate sight is the reading between Back-sight and Fore-

sight.

Change point(or Turning Point): A change point is an arbitrary point which enables the

levelling to continue from a new instrument position.It is often also termed a turning point.

The line of collimation:It is the elevation of the optical axis of the telescope at the time of the

setup. The line of collimation is the imaginary line at the elevation.

Station:It is the point where the levelling staff is kept.

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1.3 Vertical Control (Benchmark) Surveys

(i) Height of collimation method

Image source:http://gmba-learning-gateway.co.uk/images/Height_of_Col.jpg?713

(ii) Rise and Fall method

Image source:http://gmba-learning-gateway.co.uk/images/Rise_Fall.jpg?713

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1.4 OUTLINE OF APPARATUS

Automatic level is the most commonly used in

measuring, surveying, and setting horizontal and

vertical levels. The instrument is normally situated on a

tripod and then calibrated to a leveled position using

leveling screws. The operator of the automatic level

then looks through the telescope attached to the

instrument, while a second person holds a graduated

staff or tape measure at the position under

measurement.

Optical plummet is used in place of a plumb bob to center transits and theodolites over a

given point. The marked point should be located at the center of the point in the bull’s eye.

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An adjustable tripod is a three-legged stand, important in providing the foundation for the

automatic level. The three ‘legs’ can be adjusted easily to be set up on uneven surface,even

on a very steep slope. It can be easily transport from one point to another due to its

retractable legs.

Horizontal bubble level is used to determine whether

the surface is horizontal. The bubble must be located

inside the circle to ensure that the level rods and

sighting poles are in vertical position.

Levelling staff,also called as levelling rod. It is used to measure

the differences in height between the points or height of the points

above a datum surface.

2.0 OBJECTIVES

● To give definitions as a base for the proper understanding of levelling.

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● To determine the point at required elevation respect to datum.

● To learn the way to set up and operate the apparatuses for the field work

● To allow the students to apply the theories learnt in the lecture in a hand-on situation

● To have a better understanding the bookings in levelling

● To measure and record down BS (Backsight),IS (Intermediate sight) and FS

(Foresight) reading

● To determine whether the results of the levelling is acceptable by calculating the

error of misclosure with the formulae

● To identify the reduced level of each station

● To analyze the data and adjust the reduced level with the corrections

3.0 FIELD WORK MAP

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Figure above shows the points of the fieldwork at Taylor’s University Carpark

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3.1 RISE AND FALL METHOD

BS IS FS RISE FALL R.L. Remarks

1.110 100.000 BM101

1.420 2.560 1.450 98.550 A

1.480 1.460 0.040 98.510 B

1.330 1.180 0.300 98.810 C

1.570 1.430 0.100 98.710 D

1.120 0.450 99.160 E

1.480 1.180 0.060 99.100 F

1.530 1.570 0.090 99.010 G

1.420 0.110 99.120 H

1.690 1.430 0.010 99.110 I

1.570 1.280 0.410 99.520 J

1.110 0.460 99.980 BM101

Σ(BS)=13.180 Σ(FS)=13.200 ΣR=1.730 ΣF=1.750

Arithmetical check:Σ(BS) - Σ(FS) = ΣR - ΣF = Last Reduced Level Reading - First Reduced Level Reading

Σ(BS) - Σ(FS) = 13.180 - 13.200 = -0.020

ΣR - ΣF = 1.730 - 1.750 = -0.020

Last Reduced Level Reading - First Reduced Level Reading = 99.980 - 100.00 = -0.020Acceptable Misclosure= ±12√k

K= Number of set-ups±12√k = ±12√9 = 36.000mm (If the error is more than 36.000mm,then it is not acceptable)

Therefore, this levelling is acceptable.

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3.2 THE HEIGHT OF COLLIMATION METHOD

BS IS FS H.I R.L. Remarks

1.110 101.110 100.00 BM101

1.420 2.560 99.970 98.550 A

1.480 1.460 99.990 98.510 B

1.330 1.180 100.140 98.810 C

1.570 1.430 100.280 98.710 D

1.120 99.160 E

1.480 1.180 100.580 99.100 F

1.530 1.570 100.540 99.010 G

1.420 99.120 H

1.690 1.430 100.800 99.110 I

1.570 1.280 101.090 99.520 J

1.110 99.980 BM101

Σ(BS)=13.180 Σ(FS)=13.200

Arithmetical check:-Σ(BS) - Σ(FS) = Last Reduced Level Reading - First Reduced Level Reading

Σ(BS) - Σ(FS) = 13.180 - 13.200 = -0.020

Last Reduced Level Reading - First Reduced Level Reading = 99.980 - 100.00 = -0.020Acceptable Misclosure= ±12√k

K= Number of set-ups±12√k = ±12√9 = 36.000mm (If the error is more than 36.000 mm,then it is not acceptable)

Therefore, this levelling is acceptable.

3.3 Adjusted Data

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RISE AND FALL METHOD

BS IS FS RISE FALL R.L. Adj. Final R.L. Remarks

1.110 100.000 100.000 BM101

1.420 2.560 1.450 98.550 +0.0022 98.552 A

1.480 1.460 0.040 98.510 +0.0044 98.514 B

1.330 1.180 0.300 98.810 +0.0066 98.817 C

1.570 1.430 0.100 98.710 +0.0088 98.719 D

1.120 0.450 99.160 +0.0110 99.171 E

1.480 1.180 0.060 99.100 +0.0132 99.113 F

1.530 1.570 0.090 99.010 +0.0154 99.025 G

1.420 0.110 99.120 +0.0176 99.138 H

1.690 1.430 0.010 99.110 +0.0198 99.130 I

1.570 1.280 0.410 99.520 +0.0220 99.542 J

1.110 0.460 99.980 +0.0242 100.0042

≈100.000

BM101

Σ(BS)=

13.180

Σ(FS)=

13.200

ΣR=

1.730

ΣF=

1.750

Correction per set-up= Error Distribution ÷ Number of set-up

Correction per set-up= (99.980 - 100.000) ÷ 9

= - 0.020 ÷ 9

= 0.0022 m

3.4 ADJUSTED DATA

THE HEIGHT OF COLLIMATION METHOD

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BS IS FS H.I R.L. Adj. Final R.L. Remarks

1.110 101.110 100.00 100.000 BM101

1.420 2.560 99.970 98.550 +0.0022 98.552 A

1.480 1.460 99.990 98.510 +0.0044 98.514 B

1.330 1.180 100.140 98.810 +0.0066 98.817 C

1.570 1.430 100.280 98.710 +0.0088 98.719 D

1.120 99.160 +0.0110 99.171 E

1.480 1.180 100.580 99.100 +0.0132 99.113 F

1.530 1.570 100.540 99.010 +0.0154 99.025 G

1.420 99.120 +0.0176 99.138 H

1.690 1.430 100.800 99.110 +0.0198 99.130 I

1.570 1.280 101.090 99.520 +0.0220 99.542 J

1.110 99.980 +0.0242 100.0042

≈100.000

BM101

Σ(BS)=1

3.180

Σ(FS)=1

3.200

Correction per set-up= Error Distribution ÷ Number of set-up

Correction per set-up= (99.980 - 100.000) ÷ 9

= - 0.020 ÷ 9

= 0.0022 m

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4.0 DISCUSSION

For this levelling fieldwork, we have chose the car park area in Taylor’s University

Lakeside Campus as the venue for the survey work. Initially, the reduced level of

Bench Mark 1 (BM 1) is given to be 100.00 m.

To start up the leveling process, the apparatus is set up over turning point 1 and the

reading is made by obtaining the reading of the staff held vertically over the

backsight (BS) of BM1 and the foresight (FS). Then we shifted the auto level to

obtain the backsight (BS) of turning point (TP 1) and the foresight (FS) of turning

point 2 (TP 2). This process is repeated by shifting the auto level to obtain the

backsight (BS) and foresight (FS) of the following staff stations. After that we went

back to Bench Mark 1 (BM 1) in order to obtain its FS and after that we calculated

the error of misclosure.

After completed the leveling, we decided to use two different methods which are the

height of collimation and rise and fall method to calculate the reduced level of each

staff station. The error of collected data misclosure is 0.018 mm. According to the

third order of accuracy, the maximum allowable error of closure is calculated by

using the formulae of ±12√k , where k represents the number of set-ups, which then

gives the value of ±39.80mm. Hence, our data obtained is acceptable.

Therefore, each set-up is adjusted by adding equivalent value which is calculated by

distributing the error obtained to each set-up and so, the reduced level is able to be

identical to the benchmark 100.00 m.

There are few natural factors which causes occurrence of errors:

1. The curvature of the earth may affect the staff reading when the distance of

sight is long.

2. The effect of refraction may cause a wrong staff reading.

3. High velocity wind may cause a wrong staff reading as well.

Other possible errors includes the following:

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1. Foresight and backsight reading not being taken on exactly the same point.

2. Reading the staff upward instead of downward.

3. Reading of stadia hair.

4. Reading of wrong metre and decimetre.

5. Entering backsight in F.S. or vice versa.

6. Transposing the figures.

7. Omitting an entry.

8. The levelling staff is not fully extended.

It is compulsory for us as a future quantity surveyor to have some hands-on skill on a

levelling is done. Additional knowledge of site surveying which is inter-related to the

construction process may be useful in future times. Surveying is the technique,

profession, and science of determining the dimensions and contour of the Earth's

surface.

Using specialized surveying equipment such as automatic level, leveling rod, tripod

and so on, we are then armored with supplementary skills which can be said as an

advantage to us when competing with other surveyors out there. It seems to be

important as a consumer is to acquire the assistance of a surveyor is the acquisition

of a new piece of land, as it has to be legally determined where one person's

property ends and another begins for government issued deeds. Additionally,

surveyors work with cartographers to create accurate maps.

Each member contributes in this survey work and to propose this report. Discussion

is made to further our thinking incorporate with explanations our lecturer to gain

deeper understanding. It is a great experience to conduct such survey work as this is

the first time we are exposed to the method and instrument. We have done all work

on time as we follow the procedures and precautions to obtain data that its error has

been minimized to an accepted level. Hence, we can see that teamwork plays a vital

position in completing a task given and shorten the time needed to complete the

task.

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