SURVEYING - THE GATE COACH

Civil Engineering
Surveying
SURVEYING
TABLE OF CONTENTS
CHAPTER
DESCRIPTION
PAGE NO
1
Fundamental Definations and Concepts
2-5
2
Accuracy and Erros
6-8
3
Linear Measurements
9 – 15
4
Chain Surveying
16 – 18
5
The Compass
19 – 22
23 – 26
6
Traverse Surveying
7
Levelling
27 – 33
8
Contouring
34 – 35
9
Plane Table Surveying
36 – 37
10
Photogrammetric
38 - 60
11
Curve
61- 125
12
Level 1
126 – 134
13
Level 2
135 - 144
14
Level 3
145 – 150
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Civil Engineering
Surveying
Chapter 1
Fundamental Definitions and Concepts
Surveying Object
Surveying is the art of determining the relative positions of points on. above or beneath the
surface of the earth by means of direct or indirect measurements of distance, direction and
elevation. It also includes the of establishing points by predetermined angular and linear
measurements. The application of surveying requires skill as well as the knowledge of
mathematics, physics, and to some extent, astronomy. Thus, primarily; surveying can be divided
into two classes:
(1) Plane Surveying.
(2) Geodetic Surveying.
Plane surveying: is that type of surveying in which the mean surface of the earth is considered
as a plane and the spheroidal shape is neglected. All triangles formed by survey lines are
considered as plane triangles.
Geodetic surveying: is that type of surveying in which the shape of the earth is taken into
account. All lines lying in the surface are curved lines and the triangles are spherical triangles.
It, therefore, involves spherical trigonometry.
Classification: Surveys may be classified under headings which define the uses or purpose of
the resulting maps.
Classification Based Upon the Nature of the Field Survey
(a) Land Surveying:
( b ) Topographical Surveys: This consists of horizontal and vertical location
certain
points by linear and angular measurements and is made to determine the natural features
of a country such as rivers, streams, lakes, woods, hills, etc., and such artificial features
as roads, railways, canals, towns and villages.
( c ) Cadastral Surveys: Cadastral surveys are made incident to the fixing of property lines, the
calculation of land area, or the transfer of land property from one owner to another. They are
also made to fix the boundaries of municipalities and of State and Federal jurisdictions.
( d ) City Surveying: They are made in connection with the construction of streets, water supply
systems, sewers and other works.
Marine or Hydrographic Survey. Marine or hydrographic survey deals with bodies of water for
purpose of navigation, water supply, harbor works or for the determination of mean sea level.
The work consists in measurement of discharge of streams, making topographic survey of
shores and banks, taking and locating soundings to determine the depth of water and observing
the fluctuations of the ocean tide.
(b) Classification Based on the Object of Survey
(1) Engineering Survey. This is undertaken for the determination of quantities or to
afford sufficient data for the designing of engineering works such as roads and reservoirs, or
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Civil Engineering
Surveying
those connected with sewage disposal or water supply. Military Survey. This is used for
determining points of strategic importance. Mine Survey. This is used for the exploring mineral
wealth. Geological Survey. This is used for determining different strata in the earth's crust.
(c)Classification Based on Instruments Used
An alternative classification may be based upon the instruments or methods employed, the chief
types being:
Chain survey
(1) Theodolite survey
(2)Traverse survey
(3) Triangulation survey
(3) Tacheometric survey
(4) Plane table survey
(5) Photogrammetric survey and
(6) Aerial survey.
Principles of Surveying
The fundamental principles upon which the various methods of plane surveying are based are
of very simple nature and can be stated under the following two aspects :
(1) Location of a point by measurement from two points of reference : The relative
positions of the points to be surveyed should be located by measurement from at least two
points of reference, the positions of which have already been fixed. Let P and Q be the
reference points on the ground. The distance PQ can be measured accurately and the relative
positions of P and Q can be plotted on the sheet to some scale. The points P and Q will thus
serve as reference points for fixing the relative positions of other points. Any other point, such
as R, can be located by any of the following direct methods
Distances PR and QR can be measured and point R can be plotted by swinging the two arcs to
the same scale to which PQ has been plotted. The principle is very much used in chain
surveying. A perpendicular RS can be dropped on the reference line PQ and lengths PS and
SR are measured. The point R can then be plotted using set square. This principle is used for
defining details. The distance QR and the angle PQR can be measured and point R is plotted
either by means of a protractor or trigonometrically principle is used in traversing. In this
method, the distances PR and QR are not measured but angle RPQ and angle RQP are
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Civil Engineering
Surveying
measured with an angle-measuring instrument. Knowing the distance PQ, point R is plotted
either by means of a protractor or by solution of triangle PQR principle is very much used in
triangulation and the method is used for very extensive work. Angle RQP and distance PR are
measured and point R is plotted either by protracting an angle and swinging an arc from P or
plotted trigonometrically. This principle, used in traversing, is of minor utility.
(2) Working from whole to part
The second ruling principle of surveying, whether plane or geodetic, is to work from whole to
pan. It is very essential to establish first a system of control points and to fix them with higher
precision. Minor control points can then be established by less precise methods and the details
can then be located using these minor control points by running minor traverses etc. The idea of
working in thin way is to prevent the accumulation of errors and to control and localise minor
errors which, otherwise, would expand to greater magnitudes if the reverse process is followed,
thus making the work uncontrollable at the end,
Plans and Maps
A plan is the graphical representation, to some scale, of the features on. near or below the
surface of the earth as projected on a horizontal plane which is represented by 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.
The Vernier
The vernier, invented in 1631 by Pierre Vernier, is a device for measuring the fractional part of
one of the smallest divisions of a graduated scale. It usually consists of a small auxiliary scale
which slides alongside the main scale. Tlie principle of vernier is based on the fact that the eye
can perceive without strain and with considerable precision when two graduations coincide to
form one continuous straight line. The vernier carries an index mark which forms the zero of the
vernier. a vernier can primarily be divided into the following two classes : Direct Vernier
Retrograde Vernier.
( a ) Direct V ernier
A direct vernier is the one which extends or increases in the same direction as that of the main
scale and in which the smallest division on the vernier is shorter than the smallest division on
the main scale. It is so constructed that ( n - 1) divisions of the main scale are equal in length of n
divisions of the vernier. Let
s = Value of one smallest division on main scale
v = Value of one smallest division on the vernier.
n = Number of divisions on the vernier.
Since a length of (n - 1) divisions of main scale is equal to n divisions of vernier, we have
nv   n 1 s

 n 1 
v 
s
 n 
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Civil Engineering
Least count = s – v = s
Surveying
n 1
s
s
n
n
Thus, the least count (L.C.) can be found by dividing the value of one main scale division by the
total number of divisions on the venire
(2) Retrograde Vernier
A retrograde vernier is the one which extends or increases in opposite direction as that of the
main scale and in which the smallest division of the vernier is longer than the smallest division
on the main scale. It is so constructed that (n + 1) divisions of the main scale are equal in length
of n divisions of the vernier. Thus, we have, for this case
nv  n  1 s :
v
or
n 1
n
d
 n 1
s s

n
 n 
The least count  v  s  
2
 R.F.of vrongscale 
Correct length = 
  calculatedarea
R.F.of
correct
scale


Similarly. If the area of a map or plan is calculated with the help of using a wrong scale the
correct area is given by
2
 R.F.of vrongscale 
Correct area 
  calculatedarea
 R.F.of correct scale 
Shrunk Scale
If a graphical scale is not drawn on the plan and the sheet on which the plan is drawn shrinks
due to variations in the atmospheric conditions
"Shrunk scale = shrinkage factor x original scale."
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