SCHOOL OF ARCHITECTURE, BUILDING AND

DESIGN

BACHELOR OF QUANTITY SURVEYING (HONOURS)

QSB1813 – Site Surveying

Field Work Report ILevelling

August Semester 2015

Name Student ID Marks

Khoo Xin Yee 0316180

Lai Chun Foon 0315150

Hoo Bung Jiat 0314504

Kaligan 0305861

Submission Date: 2nd July 2015

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Content Page

Cover Page 1

Table of Content 2

1.0 Introduction to Leveling 3

1.1 Definition of Leveling 3 - 4

1.2 Definition of Terms Used in Leveling 4 - 6

1.3 Differential Leveling 7 - 8

1.4 Vertical Control Surveys 9 - 10

1.5 Arithmetical Check 10

2.0 Outline of Apparatus 11

2.1 Automatic Level 11 - 12

2.2 Adjustable Leg-Tripod 13 -14

2.3 Leveling Rod 14 - 15

2.4 Optical Plummet 16

2.5 Bull’s Eye Level 17

3.0 Objectives 18

4.0 Leveling Fieldwork 19

5.0 Field Data 20 - 21

5.1 Rise and Fall Method 20 - 21

6.0 Adjusted Data 22

6.1 Rise and Fall Method 22

7.0 Conclusion 23

8.0 Discussion and Recommendation 24

1.0 Introduction To Leveling

1.1 Definition of Leveling

Figure 1.0: Leveling

Source: http://www.pebblesrealty.com/images/slide2.jpg

Leveling is the process of finding the elevation at a specified location relative

to another known elevation. Levelling is the determination of the elevation of a

point or difference between points referenced to some datum. The general

term applied to any of the various processes by which elevations of points or

differences in elevation are determined. It is a vital operation in producing

necessary data for mapping, engineering design, and construction.

Levelling results are used to:

(1) Design highways, railroads, canals, sewers, water supply systems, and

other facilities having grade line that best conform to existing topography

(2) Lay out construction projects according to planned elevations

(3)  Calculate volumes of earthwork and other materials

(4)  Investigate drainage characteristics of an area

(5)  Develop maps showing general ground configurations

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(6)  Study earth subsidence and crustal motion

1.2 Definition Of Term Used in Leveling

Figure 1.3: Leveling Terms

Source: https://buildcivil.files.wordpress.com/2013/12/2.png

Level surface:

It is any surface parallel to the mean spheroidal surface of the earth e.g.

surface of a still lake. 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. It is normal to the plumb line at all points.

Level line:

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

all points.

Horizontal plane:

It is a plane tangential to the level surface at that point. It is perpendicular to

direction of gravity (plumb line).

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Horizontal line:

It is any line lying in the horizontal plane. It is a straight line tangential to a

level line.

Vertical line:

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

Vertical plane:

It is a plane containing a vertical 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 surface or line:

It is any arbitrarily assumed level surface or line from which vertical distances

are measured in India the datum adopted for G.T.S. bench marks is the mean

sea level at Karachi now in Pakistan.

Elevation:

It is vertical distance of a point above or below the datum. It is also known as

the reduced level. (R.L.) The elevation of a point is plus or minus according as

the point is above or below the datum.

Difference in elevation (H):

It is the vertical distance between the level surfaces passing through the two

different points.

Bench-mark (B.M.):

It is fixed reference point of known elevation.

Temporary benchmark (T.B.M.):

A bench-mark set up by the surveyor for his own use for particular task.

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The line of collimation:

It is the line joining the intersection of cross hairs of the optical center of the

object glass. It is also called the line of sight.

An axis of the telescope:

It is a line joining the optical center of the object glass to the center of the eye

piece.

Foresight (F.S.):

It is also called foresight reading. It is a staff (or rod) reading on a point whose

elevation is to be determined or on a change point. It is also termed as minus

sight. It is the last staff reading denoting the shifting of the instrument.

Intermediate Sight (I. S.):

It is any other staff reading taken on appoint of unknown elevation from the

same set up of the level. All sights taken between the back sight and the fore

sight and the foresight are intermediate sights.

Change Point (C. P.) or Turning Point:

It is appoint denoting the shifting of the level. It is a point on which is the fore

and back sights are taken. Any stable and well defined object such as a

boundary stone, curb stone rail, rock etc. is used as a change point. A bench

mark may also be taken as a changer point.

A Station:

It is a point whose elevation is to be determined. It may be noted that it is a

point where the staff is held not the point where they leveled is set up.

Height of instrument (H. L):

It is the elevation (or the R.L.) of the plane of collimation (or plane of sight)

when the instrument is correctly leveled. It is also called the height of plane of

the collimation.

1.3 Differential Leveling

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Differential leveling is the process of measuring vertical distances from a

known elevation point to determine elevations of unknown points. The most

common methods to determine elevation are through the use of:

A compensator type, automatic (engineering level) and level rod(s).

An electronic digital barcode leveling instrument with barcode rod.

A thorough knowledge of leveling principles and proper application of

methods and equipment will prevent costly delays and generate the needed

results and accuracy.

Figure: 1.4: Illustration of Differential Level

Source: http://onlinemanuals.txdot.gov/txdotmanuals/ess/images/ess_fig4-3_differential_leveling.jpg

The method in Figure 1.4 uses the difference in elevation between a known

elevation and the height of the instrument, and then the difference in elevation

from the height of instrument to an unknown elevation point.

A Summary of the Differential Process

A Level is setup between two points, one whose elevation is known.

Figure 1.5: Differential Leveling ProcessSource: http://jerrymahun.com/library/Elev/b.htm#B

A backsight (BS) reading is taken on the known point to determine how

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far above it the LoS is. Adding the BS reading to the point elevation

gives the elevation of the instrument (EI).

Figure 1.6: Differential Leveling Process

Source: http://jerrymahun.com/library/Elev/b.htm#B

A foresight (FS) reading is taken on the unknown point to determine

how far above it the LoS is. Subtracting the FS reading from the

instrument elevation gives the point elevation.

Figure 1.6: Differential Leveling Process

Source: http://jerrymahun.com/library/Elev/b.htm#B

The Level is moved to a position between B and the next point and the process repeated.

1.4 Vertical Control Surveys

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1.4.1 Height of Collimation Method

As explained earlier, the height of instrument (HI), e.g. the height of line of

collimation above BM (station of known level) at every instrument station is

determined through adding the backsight of BM station to decreased level of

BM. From this height of instrument at a particular instrument station,

decreased levels of all the station points on ground are computed through

substracting foresight of that particular station from HI, i.e.

HI of instrument = RL of Bench mark + BS of BM

RL of intermediate point = HI - FS at intermediate station = HI - IS

While the instrument is shifted to its second position, height of instrument at

new set up station is needed to be determined. This is achieved through

correlating the levels of two collimation planes (first and second position)

through foresight of change point from first setup station and backsight of

same change point from second setup station, as given below:

RL of change point C = RL of A + BS at A - FS at C

HI (at second station O2) = RL of C + BS at C

With instrument set up at second station (say O2), staff readings at new

system of intermediate stations are taken before shifting the instrument at

next set up station (O3). This process is continuously repeated till the

levelling exercise is done, and all the required decreased levels are acquired.

1.4.2 Rise and Fall Method

On the other hand of finding the instrument height at a setup station, the

difference between consecutive points is obtained from their staff readings

with that immediately preceding it. The difference denotes a rise or a fall. The

decrease level of each point is then acquired by adding the rise to or

subtracting the fall from the RL of the preceding point. The arithmetic check in

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this method is as follows:

∑ BS - ∑ FS = ∑ Rise - ∑ Fall

= Last RL - First RL

1.5 Arithmetical Check

An arithmetical check should be applied either at the end of the operation or

the end of each page when entries are carried forward over several pages to

avoid any possible error.

1.5.1 Height of collimation method

The sum of each collimation height multiplied by the number of reduced

levels obtained from it is equal to the sum of all the intermediate sights,

foresights and reduced levels excluding the first reduced level.

∑(BS) – ∑(FS) = Last RL – First RL

1.5.2 Rise and fall method

The sum of the back-sights minus the sum of the foresight is equal to the sum

of the rises minus the sum of the falls and is also equal to the first reduced

level minus the last reduced level.

∑(BS) – ∑(FS) = ∑(R) – ∑(F) = Last RL – First RL

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2.0 Outline of Apparatus

2.1 Automatic Level

Figure 1.7: Automatic Level

Source: http://dir.indiamart.com/mumbai/automatic-level-instrument.html

Automatic level is designed for surveyors, builders, engineers, and other

construction professionals. It is a self-leveling optical instrument for accurately

measuring horizontal planes and angles at both long and short distances.

Quick to set up and easy to use, an automatic level instrument has a built-in

compensator that takes over and precisely levels itself.

It gets its name from an internal compensation system which maintains a

horizontal LoS automatically if the instrument is disturbed. The compensation

system consists of combinations of fixed and free swinging prisms and

mirrors.

When the instrument is level the LoS is horizontal. The cross-sectional view in

Figure 1.7 shows how the incoming horizontal LoS is reflected and refracted

and emerges at the eyepiece in a parallel path.

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Figure 1.7: Automatic Level Compensator

Source: http://jerrymahun.com/library/Elev/b.htm#B

If the instrument is disturbed to an out of level condition, the compensator

moves to ensure the outgoing LoS is parallel to that of the incoming horizontal

LoS, Figure 1.8.

Figure 1.8: Compensator Correction

Source: http://jerrymahun.com/library/Elev/b.htm#B

The instrument is leveled using a circular bubble. The etched circle on the

bubble glass is a general indicator of the compensator's operating range. If

the bubble is outside the circle, the compensator may be at its physical limit

and unable to maintain a horizontal LoS.

2.2 Adjustable Leg-Tripod

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Figure 1.9: Tripod

Source: http://www.allenprecision.com/survey/robotic-total-stations/accessories/tripods

A tripod is a three-legged support platform for the level. The tripod's

primary material can be wood, metal, fiberglass, or plastic; its legs fixed length

or extendable. A tripod usually has a flat top and a mounting screw for

instrument attachment. The primary function of the tripod is to ensure a stable

instrument setup for reliable measurements.

Figure 1.10: Tripod adjustable leg

Source: http://www.levelling.uhi.ac.uk/tutorial1_1.html

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According to Figure 1.10 above, each leg of a tripod is adjustable for length.

The legs are locked by a lever clamp (left) or screw (right).

Once the legs have been set to the correct length it is important that the

locking lever or screw is tight. Otherwise, the leg may move in use which

means the instrument will have to be set up again, and all readings taken

again as the instrument height will have changed.

2.3 Leveling Rod

Figure 1.11: Level Rod

Source: http://www.allenprecision.com/media/catalog/product/cache/2/image/650x/

040ec09b1e35df139433887a97daa66f/c/s/cst_06-X05M.jpg

 A leveling rod is a surveying tool used to take elevation measurements for the

purpose of profiling a section of terrain. There are a number of basic designs

available, including versions for optical and digital sighting and record

keeping.

The rod can be constructed of wood, metal, or fiberglass. Most rods telescope

or extend in order to allow large elevation differences yet collapse into a

compact form. There are many width and gradation styles depending on

application.

The most universal design is the Philadelphia rod, a portion of which is shown

in Figure 1.11.

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Figure 1.12: Philadelphia Rod

Source: http://jerrymahun.com/library/Elev/b.htm

The red numbers are the full foot readings. The black numbers are the 0.1 ft

readings. The bars are each 0.01 ft tall and spaced 0.01 ft apart. The peaks

on the bars correspond to the adjacent 0.1 or foot reading.

A peak without an adjacent number corresponds to a half-tenth or 0.05 ft.

At distances up to about 300 feet, a Philadelphia rod can be read directly to

0.01 ft.

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2.4 Tribrach / Optical Plummet

Figure 1.13: Tribrach

Source: http://www.ebay.com/sch/sis.html?_nkw=leica%20tribrach%20gdf111%201%20with%20optical

%20plummet%20for%20total%20station%20surveying&_itemId=140696351530

A tribrach is the detachable base of all automatic level, theodolites, total

stations, forced centering targets, and most EDM’s. Tribrachs are equipped

with a bulls eye bubble for leveling and optical plummets for setting up

precisely on a survey mark. The discussion on tribrachs is conducted in a

separate section because they are being used with a wide variety of surveying

equipment.

The ability to "leapfrog" backsight, instrument point and foresight by using

interchangeable tribrachs increases the speed, efficiency and accuracy of the

traverse survey. Whenever possible, the tribrach should be detached from the

instruments and placed on the tripods for either theodolite or EDM setups.

This procedure speeds up the setting up process and protects the instrument

from accidents. In some cases, the same tribrach can be used to perform

angular or distance measurements, as well as GPS observations from the

same survey point.

2.5 Bull’s Eye Level or Horizontal Bubble Level

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Figure 1.14: Bull’s Eye Level

Source: http://www.benchmarkarizona.com/Level_Rods-8-29.html

The bull's eye level is used for maintaining both level rods and sighting poles

in a vertical position. An out of adjustment bull's eye level can cause

accumulative error in level lines. Although the sighting pole is infrequently

used for traversing, an out of adjustment bull's eye level used on sighting

poles can cause errors in both angle and distance measurements.

A simple method for checking for gross error in bull's eye level adjustment is

to check it against a previously checked door jamb or other permanent

building part. Other, more elaborate, checking procedures can be developed

using plumb lines or other devices.

3.0 Objectives

To learn the basic levelling principles, theory and applications and to

be able to book and reduce the levelling data.

To enhance the students’ knowledge in the leveling procedure.

To experience the measurement of vertical distance by leveling.

To understand the correct method of setting up automatic level, tripod

stand and other instruments.

To take and record back sight (BS), intermediate sight (IS) and fore

sight (FS) with the corrected readings.

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To understand the bookings in leveling.

To learn and undertake site measurements and calculations using

proper equation table.

To determine the error of misclosure in order to determine if the

leveling is acceptable.

To identify the reduced level of each staff station.

To plot a longitudinal profile and cross section with a suitable scale.

4.0 Leveling Fieldwork (Taylor’s Univeristy Lakeside Campus Carpark)

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Figure 1.14: Fieldwork (Carpark) – plan of the checkpoints

Source: http://dearasis.blogspot.com/2010/02/taylors-lakeside-campus.html

5 .0 Field Data

5.1 Rise and Fall Method

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Arithmetical Check:

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BS IS FS Rise Fall R.L. Remarks

1.116 100.000 BM 1

3.231 0.974 0.142 100.142 TP 1

1.086 1.159 2.072 102.214 TP 2

1.026 1.189 0.103 102.111 TP 3

1.391 1.059 0.033 102.078 TP 4

0.726 1.094 0.297 102.375 TP 5

1.101 0.979 0.253 102.122 TP 6

1.186 0.904 0.197 102.319 TP 7

1.126 1.234 0.048 102.271 TP 8

0.996 0.969 0.157 102.428 TP 9

0.951 3.359 2.363 100.065 TP 10

0.999 0.048 100.017 BM 1

∑BS=13.936 ∑FS=13.919 ∑Rise=2.865 ∑Fall=2.848

∑BS - ∑FS = ∑Rise - ∑Fall = Last Reduced Level Reading - First

Reduced Level Reading

∑BS - ∑FS = 13.936 – 13.919

= + 0.017

∑Rise - ∑Fall = 2.865 - 2.848

= + 0.017

Last Reduced Level Reading - First Reduced Level Reading

100.017 - 100.000 = + 0.017

Acceptable Misclosure =  ±12√k

K= the number of set-ups

±12√11 = 39.799 mm

(* If the error is bigger than 39.799 mm, then the levelling is not acceptable)

Therefore, the leveling is acceptable.

6.0 Adjusted Data

6.1 Rise and Fall Method

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Correction = Cumulative distance ÷ Total distance × Error

Correction per set-up

= Error of misclosure ÷ Number of set up

= (100.0000 - 100.017) ÷ 11

= - 0.0015 m

7.0 Conclusion

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BS IS FS Rise Fall R.L. Adj. Final

R.L.

Remarks

1.116 100.000 100.000 BM 1

3.231 0.974 0.142 100.142 -0.0015 100.141 TP 1

1.086 1.159 2.072 102.214 -0.0030 102.211 TP 2

1.026 1.189 0.103 102.111 -0.0045 102.066 TP 3

1.391 1.059 0.033 102.078 -0.0060 102.072 TP 4

0.726 1.094 0.297 102.375 -0.0075 102.368 TP 5

1.101 0.979 0.253 102.122 -0.0090 102.113 TP 6

1.186 0.904 0.197 102.319 -0.0105 102.309 TP 7

1.126 1.234 0.048 102.271 -0.0120 102.259 TP 8

0.996 0.969 0.157 102.428 -0.0135 102.415 TP 9

0.951 3.359 2.363 100.065 -0.0150 100.050 TP 10

0.999 0.048 100.017 -0.0170 100.000 BM 1

In this leveling fieldwork, we have learnt the procedure of leveling throughout

the car park area. Initially, the given reduced level of Bench Mark 1 (BM 1) is

100.00 m.

The leveling process begins with obtaining the backsight (BS) of BM1 and the

foresight (FS) of turning point 1 (TP 1). 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 in

order to calculate the error of misclosure.

After completed the leveling, we decided to use the rise and fall method to

calculate the reduced level of each staff station. Our error of collected data

misclosure is 0.018 mm. According to the third order of accuracy, the

maximum allowable error of closure is ±39.80mm by using the formulae of

±12√k, where k represents the number of set-ups. Thus, our leveling result is

acceptable.

Hence, the reduced level is able to be equivalent to the benchmark given

which is 100.00 m by distributing the error to each set-up.

As a future Quantity Surveyor, it is essential for us to learn some of the

knowledge of site surveying which is inter-related to the construction process.

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, professional surveyors determine land boundaries for a

variety of important reasons. One of the most common reasons for a

consumer 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.

8.0 Discussion and Recommendation

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1 Avoid taking measurement near magnetic sources such as hand phone,

watch, electric cable and etc.

2 Make sure the bubbles are properly level.

3 Triple check with the work and reading.

4 Make sure the plum bob properly centered over the peg.

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