SURVEYING – I (CE- 128)
COURSEPACK FOR UG
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o OBJECTIVES
o COURSE OUTLINE
o DETAILED SYLLABUS
o LESSON PLAN
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OBJECTIVES
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OBJECTIVES
o To enable students to understand theory and
practical of surveying
o To develop skills to use the modern survey
instruments
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COURSE OUTLINE
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COURSE OUTLINE
o COURSE TITLE: SURVEYING – I
o COURSECODE:
CE – 128
o CREDIT HRS:
THEORY:
PRAC:
3
2
1
o NO. OF WEEKS: 18
o INSTRUCTOR:
ENGR MUHAMMAD AMMAR
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SCHEDULE
o WEEK # 01: General Introduction to Survey (Lec 1)
o WEEK # 02: Distance Measurement & Chain/Compass
Surveying (Lec 2)
o WEEK # 03: Plane Table Surveying (Lec 3)
o WEEK # 04: Traversing (Lec 4)
o WEEK # 05: Traversing (Lec 5)
o WEEK # 06: Traversing (Lec 6)
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o WEEK # 07: Leveling (Lec 7)
o WEEK # 08: Leveling (Lec 8)
o WEEK # 09: Leveling (Lec 9)
o WEEK # 10: Contouring (Lec 10)
o WEEK # 11: Contouring (Lec 11)
o WEEK # 12: Computation of Areas (Lec 12)
o WEEK # 13: Computation of Volumes (Lec 13)
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o WEEK # 14: Modern Instruments in Survey (Lec 14)
o WEEK # 15: Modern Instruments in Survey (Lec 15)
o WEEK # 16: Practical Survey Training (SURVEY WEEK)
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DISTRIBUTION OF MARKS
o THEORY
4 x Quiz
2 x Assignment
2 x One Hour Test (OHT)
1 x Final Exam
15 Marks
05 Marks
30 Marks
50 Marks
o PRACTICAL*
Practical Work/Projects
Final (Viva)
Performance in field work/attendance
60 Marks
30 Marks
10 Marks
* Details will be conveyed to you before the start of survey week
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RECOMMENDED BOOKS
o Surveying Principles and Applications by Kavanagh
o Surveying and Leveling Vol. 1 by Kanetkar
o Surveying for Construction by Irvine (Reference Book)
o Surveying Theory and Practice by Davis; McGraw Hill
(Reference Book)
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DETAILED SYLLABUS
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DETAILED SYLLABUS
1. GENERAL INTRODUCTION: Definition of survey, principle of survey,
types of survey, classification of survey, instruments used in survey,
precision and accuracy, accuracy ratio, scale and its construction,
distance measurement and use of instrument for distance
measurement, errors, distance measured by tape and errors involved,
methods of chain surveying and errors involved.
2. PLANE TABLE SURVEYING: Part and accessories of plane table, setting
and orientation, methods of plane tabling.
3. TRAVERSING: Methods of traversing, bearings and calculation of
angles from bearings, traversing with chain and compass.
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4. LEVELING: Definitions, types of levels, Staff, principles of leveling,
reduction of levels, profile leveling, curvature, refraction, effect of
curvature and refraction, corrections, barometric leveling,
hypsometry, errors in leveling.
5. CONTOURING: Definitions, characteristics & uses, locating contours,
interpolation of contours, setting grade stake for sewers.
6. COMPUTATION OF AREAS: introduction, determination of areas,
computation of areas from plans, trapezoidal rule, simpson rule
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8. COMPUTATION OF VOLUMES: measurement of volumes from crosssections and various formulas for computation of volumes,
determination of capacity of reservoir.
9. MODERN METHODS IN SURVEYING: principles of EDMI, EMD
characteristics, total station, Global Position System.
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LESSON PLAN
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LECTURE # 01: INTRODUCTION TO SURVEY
1.
2.
Definition: - Surveying is the art of making such measurements as will determine
the relative positions of distinctive features on the surface of the earth in order that
the shape and extent of any portion of earth`s surface may be ascertained and
delineated on a map or plan. It is essentially a process of determining positions of
points in a horizontal plane. OR
Surveying is the art and science of measuring distances, angles & positions, on or
near the surface of the earth.
“Leveling is art of determining the position of point in vertical plane”.
Object of Survey:  The primary object of surveying is the preparation of a plan or map.
 A plan is therefore, the projected representation to some scale, of the ground
and the object on the horizontal plane which is represented by the plane of the
paper on which the plan is drawn. The representation is called a map, if the
scale is small, while it is called a plan, if the scale is large, e.g. a map of UK, a
plan of a building.
 The science of surveying has been developing from the very initial stage of
human civilization according to his requirement. Earliest surveys were
performed only for the purpose of demarcating its boundaries of plots of land.
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

3.
Due to advancement in technology, the science of surveying has also attained
its due importance. In the absence of accurate maps, it is impossible to lay out
the alignments of roads, railways, canals, tunnels, transmission power lines, &
microwave or television relaying towers.
Detailed map of the sites of engineering projects are necessary, therefore,
surveying is the first step in the execution of any project
Types of Surveys:

(1) Plane Surveying and (2) Geodetic Surveying
Plane surveying: In plane surveying the curvature of the earth is not taken into
account, as the surveys extend over small areas. In dealing with plane surveys,
the knowledge of plane geometry & trigonometry is only required. Surveys
covering an area up to 260 sq. km may be treated as plane surveys because
the difference in length between the arc & the subtended chord on the earth
surface for a distance of 18.2km is only 0.1m.
Scope & Use of Plane Surveying: Plane Surveys are carried out for
engineering projects on sufficiently large scale. They are used for the layout of
highways, railways, canals, fixing boundary pillars, construction of bridges etc.
For majority of engineering projects, plane surveying is the first step to execute
them.
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

Geodetic Surveying: The surveys in which curvature of the earth is taken into
account & higher degree of accuracy in linear as well as angular observations
is achieved are known as Geodetic Surveying. As the surveys extend over
large areas, lines connecting any two points are on the surface of the earth are
treated as arcs. A knowledge of spherical trigonometry is necessary for making
measurements for the geodetic surveys.
Scope & Use of Geodetic Surveying: Geodetic Surveys are conducted with
highest degree of accuracy to provide widely spaced control points on the
earth’s surface for subsequent plane surveys. In Pakistan, Geodetic Surveys
are usually carried out by the survey of Pakistan.
4. Classification
Surveys may be classified in a variety of ways:
a.
Classification based upon the nature of the field of survey:
(1)
Land Surveys.
(2)
Hydrographic Surveys.
(3)
Astronomical Surveys.
b.
(1)
(2)
Classification based upon the object of survey:
Archaeological Surveys for unearthing relics of antiquity
Geological Surveys for determining different strata in the earth’s crust.
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(3)
(4)
(5)
Mine Surveys for exploring mineral wealth such as gold, coal, etc.
Military Surveys for determining points for strategic importance both
offensive and defensive.
Engineering Surveys for determination of quantities for designing
engineering works.
c.
(1)
(2)
Classification based upon the methods employed in survey:
Triangulation Surveys.
Traverse Surveys.
d.
(1)
(2)
(3)
(4)
(5)
(6)
Classification based upon the instrument employed:
Chain Surveys.
Theodolite Surveys.
Tachometric Surveys.
Compass Surveys
Plane Table Surveys.
Photogrammetric Surveys.
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6.
Land surveys may be further sub-divided into the following classes:
(a)
Topographical Surveys for determining the natural features of a
country such as hills, valleys. Rivers, nallas, takes, woods, towns, villages etc.
(b)
Cadastral surveys in which additional details such as boundaries of
fields, houses and other properties, path ways, are determined.
(c)
City Surveys for laying out plots and constructing streets, water supply
systems, and sewers.
7.
Engineering Surveys may be further sub-divided into:
(i)
Reconnaissance surveys for determining the feasibility and rough cost
of the scheme.
(ii)
Preliminary surveys for collecting more precise data to choose the
best location for the work and to estimate the exact quantities and costs
(iii)
Location surveys for setting out the work on the ground.
8.
Principles of Surveying: various survey methods are based are:
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The two fundamental principles upon which
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1. To work from the whole to the part: The main principle of
surveying is to work from the whole to the part. To achieve this in actual practice, a
sufficient number of primary control points are established with higher precision in &
around the area to be detail surveyed. Minor control points in between the primary
control points are then established with less precise method. Further details are
surveyed with the help of these minor control points by adopting any one of the survey
methods. The main idea of working from the whole to the part is to prevent
accumulation of error & to localize minor errors within the framework of the control
points. On the other hand, if survey is carried from the part to the whole, the errors
would expand to greater magnitudes & the scale of the survey will be distorted beyond
control.
2. Location of a point by measurement from two control points:
The control points are selected in the area & the distance between them is measured
accurately. The line is then plotted to a convenient scale on a drawing sheet. The
location of the required point may then be plotted by making two measurements from
the given control points as follow:
Let A & B be two given control points. Any other point, say D can be located
with reference to these points, by any one of the following method:
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• Rectangular coordinates by the perpendicular dD and the distance Ad. The
distance Bd may be measured instead of Ad (fig--)
• Trilateration: by the two distances AD and BD (fig--)
• Polar coordinates: the angle BAD measured at A and the distance AD.
Instead, by angle DBA measured at B and the distance BD (fig--)
• Triangulation: by the two angles BAD and ABD measured at A and B (fig---)
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9. Scales: - The scale of a map or plan is the fixed proportion which every distance between the
locations of the points on the map or plan bears to the corresponding distance between
their positions on the ground. Thus if 1 cm on the map represents 10 m on the ground, the
scale of the map is 10 m to 1 cm often written simply as 1 cm = 10m. The scale is also
expressed by means of a regular fraction whose numerator is invariably unity. The fraction
is called “Representative Fraction (R.F)”.For example, if the scale is 10m to 1cm, the
R.F. of the scale is
Scales of the maps are represented by the following two methods:
a). NUMERICAL SCALES
b). GRAPHICAL SCALES
Characteristics of a Scale Line: a. It should be sufficiently long. (Usually between 18 cm to 27 cm but not more than
32 cm)
b. It should be accurately divided and carefully numbered.
c. The zero must always be placed between the unit and its subdivisions.
d. The name of the scale together with its representative fraction should be
written on the plan.
e. It should be easily read and should not involve any arithmetic calculation in
measuring distance on the map. The main divisions should, therefore, represent one,
ten, or hundred units.
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Plain Scale: On a plain scale it is possible to read only two dimensions such as
meters and decimeters, units and tenths etc.
Example: Draw a scale 1cm = 4m to read to a meter and show on it 47m.
Const: Draw a line 20 cm long and divide it into eight equal parts. Subdivide the
first division from the left into 10 equal parts each subdivision reading 1 meter. Place the
zero between the subdivided part and the undivided part and mark the figures counting
from zero in both dir. To read 47m place one leg of the dividers at 40 and the other at 7.
10. Stages of Survey Operations: The entire work of a survey operation may be
divided into three distinct stages:
1. Field work-Reconnaissance, Observations, Field Records
2. Office work-Drafting, Computing, Designing
3. Care & adjustment of the instruments
11. Accuracy Of Surveyed Quantities:
 Surveyors’ primary objective is to achieve accuracy in their measurements.
 Survey is of little value if it is not accurate.
 In surveying, the most common task is to find the 3D positions of a series of
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points, the x, y & z coordinates. Physical measurements are therefore
required in the form of linear, angular & height dimensions. There will be
error in these quantities which must be eliminated, discounted or distributed.
a). Classification of Errors:
Gross: They are simply mistakes. They arise mainly due to the
inexperience, ignorance or carelessness of the surveyor. These errors
cannot be accommodated & observations have to be repeated.
Examples: reading the tape wrongly, recording a wrong dimension when
booking, turning the wrong screw on an instrument.
Systematic: These are errors which arise unavoidably in surveying & follow
some fixed law. Their sources are well known. A simple example is
illustrated by the temp error in tape measurements. A tape is only correct at
a certain standard temp; therefore if the ambient temp on a certain day is
higher or lower than standard, the tape will expand or contract & cause an
error which will be the same no matter how often the line is measured.
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Constant: These are errors which do not vary at any time, in other words,
they have the same sign, either positive or negative. As an illustration,
consider the nature of the dimensions required for plotting on maps & plans.
These must be horizontal & if no attention is paid to the slope of the ground
when making a measurement, the dimension so obtained will be too long.
No matter how often the measurement is made or how many other slopes
are measured, the results will always be too long.
Likewise, if a tape has stretched through continuous use, any resultant
measurements will always be too short.
Constant errors are well known & appropriate corrections are applied
to obtain the correct result.
Accidental/Random: These are the small errors which inevitably remain
after the others have been eliminated. There are three main causes:
Imperfections of human sight & touch (human errors), Imperfections of the
instruments being used at the time & Changing atmospheric conditions.
A good example arises in the measurement of an angle using an
instrument called a theodolite.
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b). Accuracy & Precision: Accuracy & Precision are not synonymous. The
difference is illustrated in the following example:
A line of survey is measured six times & all six measurements lie
within an error band of ± 2mm. However, the tape when checked, is found
to have stretched by 10mm through continuous use.
The results of the six measurements are precise in that they have little
scatter but they are not accurate because each is in error by 10mm.
In surveying, accuracy is defined by specifying the limits between
which the error of a measured quantity may lie, for example, the accuracy of
the measured building might be (20.54 ± 0.01) metres.
Accuracy Ratio: The accuracy ratio of a measurement or series of
measurements is the ratio of error of closure to the distance measured. The
error of closure is the difference between the measured location & the
theoretically correct location.
To illustrate, a distance was measured & found to be 250.56 ft. The
distance was previously known to be 250.50 ft. The error is 0.06 ft in a
distance of 250.50 ft.
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accuracy ratio = 0.06/250.50 = 1/4175 = 1/4200
The accuracy ratio is expressed as a fraction whose numerator is unity &
whose denominator is rounded to the closest 100 units.
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LECTURE: DISTANCE MEASUREMENT
 Two main methods of determining the distances between points on the surface of the
earth.
 Direct Measurement: distances are actually measured on the surface of the earth by
means of chains, tapes etc.
 Computative Measurement: Distances are determined by calculations indirectly by
using the field data as in triangulation, tacheometry etc.
 Instruments for Measuring Distances:
1). Chain-Gunter’s Chain (66ft), Engineer’s Chain(100ft), Metric Chain(20/30m)
2). Steel Band
3). Tapes-Cloth/Linen Tape, Metallic Tape, Steel Tape, Invar Tape
 Arrows/Chain Pins: 10 arrows generally accompany a chain, used to mark the end
of each chain during the process of chaining.
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 Instruments for Marking Stations:
1). Pegs
3). Ranging Poles
2). Ranging Rods
4). Offset Rod
5). Plumb Bobs
 Ranging a Line: The process of marking a number of intermediate points on a survey
line joining two stations in the field so that the length between them may be measured
correctly, is known as ranging.
Ranging may be classified as DIRECT RANGING & INDIRECT RANGING
 Direct Ranging: When intermediate ranging rods are placed along the chain line, by
direct observation from either end station, the process is known as direct ranging.
 Line Ranger: It is a small reflecting instrument used for fixing intermediate points on
a chain line.
 Indirect Ranging: When end stations are not intervisible & the intermediate ranging
rods are placed in line by interpolation or by reciprocal ranging or by running an auxiliary
line (or random line), the process is known as Indirect Ranging.
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 Degree of Accuracy in Chaining: For comparison of precision of chaining when line
of different lengths are measured under dissimilar conditions, it is the usual practice to
express the error as ratio (1:n), which is called the chaining ratio. It is the ratio of the
error to the distance measured.
EXAMPLE: 1/1500, 1/5000 etc. By this is meant an error of 1 unit in 1500 units,
or an error of 1 unit in 5000 units
The limits of errors under different conditions are as follows:
1). For ordinary measurements with a steel band on flat ground & with careful
work: 1 in 2000.
2). For ordinary measurements with a carefully tested chain on fairly level
ground & with reasonable care: 1 in 1000.
3). Under average conditions: 1 in 500.
4). For measurements over rough or somewhat hilly ground: 1 in 250.
 Error in Measurement due to Incorrect Chain Length: “If the chain is too long, the
measured distance will be less & if the chain is too short, the measured distance will be more.”
a. The true length of line = L´ / L x measured length of line
Where L´ = the incorrect length of a chain or tape
And
L = the true length of a chain or tape
Note : Use plus sign when the chain is too long and minus sign when it is too short
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b. The true area of a plot of a land = (L´/L)2 x Measured area of the plot
c. The true volume of an excavation = (L´/L)3 x Measured volume of the
excavation
 Examples on Correction of Distance and Area:
1. The length of a line measured with a 20 m chain was found to be 634.4 m. It was
afterwards found that the chain was 0.05 m too long. Find the true length of the line.
Solution:
True length of line = L’/L x measured length of line.
L’ = 20.05 m.
L = 20 m.
Measured length = 634.4 m.
Therefore,
True length of the line = 20.05/20x 634.4
= 635.586 m = 635.5 m (approx)
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2. The length of a line measured by means of a 20 m chain was found to be 610.2 m
known to be 612.0 m. What was the actual length of the chain?
Solution:
Since the measured length of the line is less than its true length, the chain was too long.
Now true length of the line = L’/L x measured length.
True length of the line = 612.0 m.
Measured length of the line = 610.2 m.
L = 20.0 m.
:.
612.0 = L’/20.0 x 610.2
:.
L’
= 612.0x20.0/610.2=20.066 m.
3. A 20 m chain was found to be 0.05 m too long after chaining 1400 m. It was found to
be 0.1 m too long after chaining 2200 m. If the chain was correct before commencement
of the work find the true distance.
Solution:
a.
Since the chain was correct i.e. 20 m long at the beginning and was 20.05 m
long after chaining 1400 m, the increase in length was gradual.
:.
Mean elongation = 0+0.05/2=0.025 m.
:.
True distance = 20.025/20 x 1400 = 1401.75m.
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b.
The remaining distance (2200-1400) = 800 m was measured with the same
chain. If was 0.05 m too long at the commencement of chaining and 0.10 m too long at
the end of chaining.
:.
Mean elongation = 0.05+0.10/2 = 0.075 m.
True distance
= 20.075/20 x 800 = 803.00m.
where, total true distance = 1401.75 + 803.00 m.
= 2204.75 m.
 CHAINING ON SLOPING GROUNDS:
1). Chaining on the surface of a sloping ground gives the sloping distance.
2). For plotting the surveys, horizontal distances are required.
3). It is therefore, necessary either to reduce the sloping distances to horizontal
equivalents or to measure the horizontal distances between the stations directly.
4).Two methods for getting the horizontal distance between two stations on a
sloping ground:
DIRECT METHOD & INDIRECT METHOD
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Fig. DIRECT
METHOD:
Horizontal distances
are measured on
the ground in short
horizontal lengths.
Also known as
‘Stepping Method’.
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Fig. INDIRECT METHOD: Measuring the slope
angle with a CLINOMETER
Fig. INDIRECT METHOD: Measuring
the slope angle from Difference in
Elevations
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Fig. INDIRECT METHOD: Hypotenusal
Allowance Correction Method
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 ERRORS IN CHAINING:
1). Cumulative Errors
2). Compensative Errors
o CUMULATIVE ERRORS: The errors which occur in the same direction & tend to
accumulate, or to add up are called Cumulative Errors. Such errors make the apparent
measurements always either too long or too short.
a). Positive Cumulative Errors: Those errors which make the measured lengths more
than the actuals are known as positive cumulative errors. These are caused in the
following situations:
i). The length of the chain or tape is shorter than its standard length.
ii). The slope correction ignored while measuring along the sloping ground.
iii). The sag correction, if not applied, when the chain or tape is suspended at
its ends.
iv). Due to incorrect alignment.
v). Due to working in windy weather.
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b). Negative Cumulative Errors: The errors which make the measured lengths less
than the actuals are known as negative cumulative errors. These are caused in the
following situations:
i).
The length of the chain or tape is greater than its standard length.
o COMPENSATING ERRORS: The errors which are liable to occur in either direction &
tend to compensate are called compensating errors. These are caused in the following
situations:
i).
Incorrect holding of the chain
ii).
The chain is not uniformly calibrated throughout its length
iii).
Refinement is not made in plumbing during stepping method
 COMMON MISTAKES IN CHAINING:
i).
Displacement of the arrows
ii).
Failure to observe the zero point of the tape
iii).
Adding or omitting a full chain length
iv).
Reading from the wrong end of the chain
v).
Reading numbers wrongly/ Reading wrong meter marks
vi).
Wrong recording in the field book
viii).
Calling numbers wrongly
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 CORRECTIONS FOR LINEAR MEASUREMENTS:
i).
Correction for Standard Length
ii).
Correction for Alignment
iii).
Correction for Slope
iv).
Correction for Temperature
v).
Correction for Tension
vi).
Correction for Sag
 CORRECTION FOR STANDARD LENGTH:
Ca = L.C/ l
where:
Ca = Correction for absolute length
L = Measured length of a line
l = nominal or designated length of the tape
C = Correction to be applied to the tape
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 CORRECTION FOR ALIGNMENT:
1). When the two stations are visible:
The Required Correction = l1(1- cos θ1) + l2(1- cos θ2)
2). When the two stations are not visible:
AB = √ [AC2 + BC2 – 2AC.BC.cosφ]
 CORRECTION FOR SLOPE:
1). CASE 1:
Let L = slope distance
D = horizontal distance
h = difference in elevations of A & B
Therefore, D = √(L2 – h2) and
Slope Correction = L – D
= h2/2L
2). CASE 2: Slope Correction = L – L cosφ = L (1 – cosφ)
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 CORRECTION FOR TEMPERATURE:
Correction for Temperature is given by the formula:
Ct = α L (Tm – To)
where:
Ct = correction for temperature
α = coefficient of thermal expansion
Tm = mean temperature during measurement
To = temperature at which the tape is standardized
L = measured length
 CORRECTION FOR PULL (TENSION):
Correction for Pull is given by the formula:
Cp = (Pm – Po) × L / AE
where:
Cp = correction for pull
Pm = pull applied during measurement
Po = pull under which the tape is standardized
A = cross-sectional area of the tape
E = modulus of elasticity of steel
L = measured length
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CORRECTION FOR SAG:
Correction for Sag is given by the formula:
Cs = l1 (Mg)2 / 24P2
where:
Cs = correction for sag
M = total mass of the tape
P = applied pull
l1 = distance between supports
 EXAMPLES ON CORRECTIONS:
1). A line was measured with a steel tape which was exactly 30m long at 18°C & found
to be 452.343m. The temperature during measurement was 32°C. Find the true length of
the line. Take coefficient of expansion of the tape per °C = 0.0000117.
Solution:
Here,
l = 30m, To = 18°C, Tm = 32°C, α = 0.0000117
Ct / unit length = 0.004914 m (+ive)
length of the tape at 32°C = 30.004914 m
Now,
True length = 30.004914/30 × 452.343 = 452.417 m
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2). A line was measured with a steel tape which was exactly 30 m at 18°C & a pull of
50N & the measured length was 459.242m. Temperature during measurement was 28°C
& the pull applied was 100N. The tape was uniformly supported during the
measurement. Find the true length of the line if the cross-sectional area of the tape was
0.02cm2, the coefficient of expansion per °C = 0.0000117 & the modulus of elasticity =
21 × 106 N/cm2.
Solution:
Here,
l = 30m, To = 18°C, Tm = 28°C, α = 0.0000117
Pm = 100N, Po = 50 N, A = 0.02 cm2, E = 21 × 106 N/cm2
correction per tape length = 0.0000117 × (28-18) × 30
Ct / unit length = 0.00351m (+ive)
pull correction per tape length = (100 - 50) × 30/(0.02 × 21 × 106)
Cp / unit length = 0.00357 (+ive)
Therefore,
combined correction = 0.00708m
True length of tape = 30.00708m
True length of the line = 459.242m
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3). A 50m tape is suspended between the ends under a pull of 150N. The mass of the
tape is 1.52 kilograms. Find the corrected length of the tape.
Solution:
Here,
l1 = 50m, M = 1.52 kg, P = 150N
Correction for sag = Cs = 50 × (1.52 × 9.81)2 / (24 × 1502)
= 0.0206 m
Corrected length of the tape = 50 – 0.0206
= 49.9794 m.
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ASSIGNMENT # 01
(DATE OF SUBMISSION: 21ST Oct, 2009)
1). A base line AC was measured in two parts along two straight drains AB & BC of
length 1650m & 1819.5m with a steel tape which was exactly 30m at 25°C at a pull of
10kg. The applied pull during measurement of both parts was 20kg whereas respective
temperatures were 45°C & 40°C. The slopes of drains AB & BC were 3° & 3°30ʹ & the
deflection angle of BC was 10° right. Find the correct length of the base line if the cross
sectional area of the tape was 0.025 sq. cm. The coefficient of expansion & modulus of
elasticity of tape material were 3.5 × 10-6 per °C & 2.1 × 106kg/cm2.
2). A survey line AB is running along different slopes. There is a downward slope of 1 in
10 from station A to chainage 238m. The ground has an angle of elevation of 8°15ʹ from
chainage 238m to chainage 465m. There is a rise of 25m from chainage 465m to station
B having chainage of 665m. All the measurements of chainages have actually been
taken along the ground. It was found that the 20m chain used for chaining was 5 cm too
long throughout the work.
Calculate the correct horizontal distances from station A to station B in the case.
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LECTURE : CHAIN SURVEYING
 CHAIN TRIANGULATION OR CHAIN SURVEYING:
It is the system of surveying in which the sides of the various triangles are
measured directly in the field and no angular measurements are taken.
It is most suitable when:
(i).
The ground is fairly level and open with simple detail.
(ii).
Plans are required on a large scale such as those of estates, fields, etc.
(iii).
The area is small in extent. It is unsuitable for large areas, and areas crowded
with many details, or difficult or wooded countries.
 PRINCIPLE OF CHAIN SURVEYING:
The principle of a chain survey is triangulation. It consists of the arrangement of
framework of triangles, since a triangle is the only simple plane figure, which can be
plotted from the lengths of its sides alone. The framework should therefore, consist of
triangles which are as nearly equilateral as possible, such triangles being known as well
conditioned, or well shaped. A triangle is said to be well conditioned or well proportioned
when it contains no angle smaller than 30o and no angle greater than 120 o. Illconditioned triangles having angles less than 30o or greater than 120o should always be
avoided. If however, they are unavoidable, great care must be taken in chaining and plotting.
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 TECHNICAL TERMS & THEIR DEFINITIONS:
1). Main Survey Station: The point where two sides of a main triangle meet is called
main survey station. Main survey station is a point of importance at the beginning & at
the end of a chain line.
2). Subsidiary Survey Station (or Tie Station): The stations which are selected on the
main survey lines for running auxiliary lines are called subsidiary stations.
3). Main Survey Lines: The chain lines joining the main survey stations are known as
main survey lines.
4). Auxiliary, Subsidiary, or Tie Lines: The chain lines joining the subsidiary survey
stations are known as auxiliary, subsidiary or more commonly as tie lines. These are
provided to locate the interior details which are far away from the main lines.
5). Base Line: The longest of the main survey lines is called a base line. Various
stations are plotted with reference to the base line.
6). Check Line: The lines which are run in the field to check the accuracy of the field
work are called check lines. If the measured length of a check line agrees with the length
scaled off the plan, the survey is accurate.
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 FIGURE: LAYOUT OF A CHAIN SURVEY:
1. Base Line; AC
2. Main Surveying Lines: AB, BC, CD & AD
3. Subsidiary or Tie lines: BE & FD
4. Check Lines: HG & MN
5. Main Surveying Stations: A, B, C & D
6. Subsidiary Stations: E & F
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 SELECTION OF STATIONS:
The following points should be kept in mind while selecting survey stations:
1). Main survey stations at the ends of chain lines should be intervisible.
2). Survey lines should be minimum possible.
3). The main principle of surveying viz., working from the whole to the part & not from
the part to the whole, should be strictly observed.
4). Survey stations should form well conditioned triangles.
5). Every triangle should be provided with a check line.
6). Tie lines should be provided to off long offsets.
7). Obstacles to ranging & chaining, if any, should be avoided.
8). The larger side of the triangle should be placed parallel to boundaries, roads,
buildings etc. to have short offsets.
9). To avoid trespassing, main survey lines should remain within the boundaries of the
property to be surveyed.
10). Chain lines should be preferably over level ground.
11). Lines should be laid on one side of the road to avoid interruption of changing by
passing traffic.
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 SELECTION & MEASUREMENT OF THE BASE LINE:
In chain surveying, the base line is the most important line as it fixes the
directions of all other chain lines. The following points are kept in view during its
selection & measurement:
1). It should be laid preferably on a level ground.
2). It should be run through the centre of the length of the area.
3). It should be correctly measured horizontally.
4). It should be measured twice or thrice & the mean distance accepted, as its correct
length.
5). Great care should be taken, to ensure straightness of the base line.
6). If convenient, two base lines perpendicular bisecting each other should be laid out.
 OFFSETS:
In chain surveying, the position of details i.e. boundaries, culverts, roads,
stream bends etc., are located with respect to the chain line by measuring their
distances right or left of the chain lines, such lateral measurements are called offsets.
There are two types of offsets: Perpendicular Offsets & Oblique Offsets
Depending upon the length, offsets are further classified as short offset (length
less than 15m) & long offsets (length more than 15m).
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 TAKING OFFSETS: Offset measurements are taken & noted in the field & the
complete operation is known as ‘taking offsets’. Offset is taken as follows in the absence
of any instrument:
The leader holds the zero end of the tape at the point P for which offset is taken & the
follower swings off the chain in a short arc about the point P as a centre. He finds the
minimum reading, which gives the position of the foot of the perpendicular from P to AB.
Such an offset is called a ‘swing offset’.
The follower then fixes an arrow at the point so found & reads the chainage & the length
of the offset. The surveyor, after checking, records the readings in a field book.
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 INSTRUMENTS FOR SETTING OUT RIGHT ANGLES:
1). Cross Staffs
2). Optical Squares
 FIELD BOOK: The book in which chainages, offset measurements & sketches of
detail points are recorded is generally called a field book. It is an oblong book of size
20cm × 12cm & opens lengthwise.
1). BOOKING FIELD NOTES: In a field book, field notes are entered from the bottom of
the page upward. At the beginning of a chain line, the following information is recorded
in the field book:
* The name or number of the chain line
* The name or number of the survey station
* The symbol
denoting the station mark
* The direction of survey lines starting off from or ending at the station
* The initial chainage which is generally zero, is enclosed in the
symbol
.
All distances along the chain line i.e. chainages are entered on the central line
or in the central column & offsets are written opposite to them on the right or left of the
column according to their ground positions with respect to the chain line. Close to the
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offsets, their sketches are drawn to guide the draftsman to draw them correctly.
Tie or subsidiary stations along a chain line should be indicated by a circleor an
oval around their chainages.
A specimen field book for chain survey is shown in the next slide:
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2). INSTRUCTIONS FOR BOOKING THE FIELD NOTES:
 Each chain line or a tie line, should be recorded on a separate page.
 The recorder should always face the direction of chaining while booking the field notes.
 All the measurements should be recorded as soon as these are taken & nothing should
be left to memory.
 The notes should be complete, neat & accurate with all information necessary for
plotting the survey by a draftsman in office.
 Numerals should be neatly & legibly written without any overwriting.
 Sketches of the details should be neat & clear.
 A good quality pencil should be used for recording the entries.
 The field book is an important document & should be kept clean. Wrong entries should
be scored out & correct ones written over the wrong ones. If an entire page is to be
discarded, it should be crossed, & marked “cancelled”. A reference to the page on which
correct readings are recorded, is made on this page.
 The complete record of the chain survey should include:
- A general layout plan of the lines
- The details of the lines
- The date of the survey
- A page index of the lines
- Names of the surveyor & his assistants
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 FIELD WORK:
- Reconnaissance
- Marking Stations
- Running Survey Lines
- REFERENCE SKETCH: The sketch, showing at least measurements to three permanent
& definite points such as gates, pillars, light posts, corner of buildings etc., is known as a
reference or location sketch.
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