49680631-surveying

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SURVEYIN

G

Prof. V. Kanakasabai PhD

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Definition

Surveying is the art ofdetermining

the relative positions ofpoints

on,above orbelowthe surface of

earth either by direct or indirectmeasurements.

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Object of surveying

The main object of any survey is to prepare a

plan or map so that it may represent the area

on a horizontal plane.

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Uses of Surveying

To show the ground features.

To fix control points and thus to establish the

boundaries.

To set out any engineering work like buildings,

bridges, roads, railway tracks and dams.

To determine the relative heights of objects/

points in a vertical plane.

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Types of Surveying

There are two types of surveying

1. Plane Surveying

2. Geodetic Surveying

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Plane Surveying

It is a type of surveying in which the earth

surface is considered as a plane and curvature

of earth is neglected.

This survey is adopted over small areas upto

260 sqkm.

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Plane Surveying

The line connecting two points on the earth is

considered as a straight line.

The triangle formed by three lines is a Plane

Triangle.

It is used for the layout of highways, railways,canals, construction of buildings, bridges,

dams, etc.

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Geodetic Surveying

It is a type of surveying in which the shape of

the earth is taken into account.

All lines lying on the surface are curved lines

and the triangle formed is a Spherical Triangle.

It will posses a high degree of accuracy as itconsiders the effect of curvature of earth.

This surveying extends over large area.

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Classification of Surveying

Depending on the use and purpose of survey,

the following are the classifications:

I . Based on the nature of the field of Survey.

Land Surveying

Astronomical Surveying

Marine or Hydrographic Surveying.

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II. Based on the object of Survey

Engineering Survey

Military Survey

Geological Survey

Mine Survey

Archaeological Survey.

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III. Based on the Instruments used

Chain Survey

Compass Survey

Plane table survey

Level Survey

Theodolite Survey

photographic Survey.

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Principles of Surveying

There are two main principles in Surveying.

1. Location of a point by measurements from

two points of reference.

2. Working from whole to part

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Principles of Surveying.

Location of a point by

measurement from two points of

referenceo Let P & Q be the reference points located on

the ground

o This line PQ can be measured accurately.

o Any other point, such as R, can be located by

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Working from whole to part

A system of control points is first established

and fixed them with higher precision

Minor control points are then established in

between the control points and details are

worked out.

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Measurements

In plane surveying four kinds of measurements

are used.

1. Horizontal Distance

2. Vertical Distance

3. Horizontal angle

4. Vertical Angle

According to the standards of weights andmeasures act (India) 1956, the unit of

measurement of distance is metres (m) and

centimetres (cm).

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The angles are measured in the sexagesimal

system.

The unit of measurement is

Degree

minutes

seconds

This system is adopted in USA, UK, India andother

European countries.

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