introduction of surveying

ENGR. SHAMS UL ISLAM

ASSISTANT PROFESSOR

CIVIL ENGINEERING DEPARTMENT

CECOS UNIVERSITY PESHAWAR

BRIEF INTRODUCTION

• Ph.D. (Structural Engineering in Progress) from CECOS

University Peshawar

• M.S (Structural Engineering) from CECOS University Pesh.

• B.S (Civil ) from UET Peshawar (Bannu)

• Teaching Experience in GCT Peshawar , GCT Nowshera

and CECOS University Peshawar

• Office located in from of Main Library CECOS Uni.

Week No.1

Surveying-I

Lecture No.1

B-Tech 2015

By:

Engr. Shams Ul Islam

Lecturer, Civil Engg. Department

CECOS University Peshawar

Surveying

Surveying is defined as “the science, art, and technology of

determining the relative positions of points above, on, or

beneath the Earth’s surface, or of establishing such points. OR It

is the art of determination of horizontal distances, differences in

elevation, directions, angles, locations, areas and volumes on or

near the surface of the earth.

4Engr.Shams Ul Islam ([email protected])

Primary Division of Surveying

Surveying may be divided into two general classes

Geodetic surveying

Plane surveying


Geodetic Surveying

It is also called Trigonometrical surveying. The object of a

geodetic surveying is to determine the precise positions on the

surface of the earth of a system of widely distant points and the

dimensions of areas. In this survey, the curvature of the earth is

taken into account, since large distances and areas are covered.


Plane Surveying

In this survey, the earth’s surface is considered as a plane. The

curvature of the earth is not taken into account, as the surveys

extend only to small areas. The line joining any two points as a

straight line and all angles are plane angles. Surveys normally

carried out for the location and construction of roads, canals

and, buildings. In general, the surveys necessary for the works

of man are plane surveys.


Classification

Surveys may be classified in a variety of ways.

I. Classification based upon the nature of the field of survey:

(a) Land Surveys.

(b) Marine or Navigation Surveys.

(c) Astronomical Surveys.

II. Classification based upon the object of survey:

(i) Archaeological surveys.

(ii) Geological Surveys -for determining different strata in the earth’s crust.

(iii) Mine Surveys- for exploring mineral wealth such as gold, coal, etc.

(iv) Military Surveys- for determining points of strategic importance both offensive

and defensive.


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III. Classification based upon the methods employed in survey:

(a) Triangulation Surveys.

(b) Traverse Surveys.

IV. Classification based upon the instrument employed:

(i) Chain Surveys.

(ii) Theodolite Surveys.

(iii) Tacheometric Surveys.

(iv) Compass Surveys.

(v) Plane Table Surveys.

(vi) Photographic and Aerial Surveys


Measurements

There are two kinds of measurements used in plane surveying

Linear

Angular

The linear measurement may be further subdivided into:

Horizontal distances

Vertical distances

The Angular measurements may be further subdivided into:

Horizontal angle

Vertical angle.


Principles of Surveying

The fundamental principles upon which the surveying is being

carried out are

1. Working from whole to part.

2. After deciding the position of any point, its reference must

be kept from at least two permanent objects or stations

whose position have already been well defined.

The purpose of working from whole to part is

• To localize the errors and

• To control the accumulation of errors.


Operation in Surveying

Different operations performed in surveying are:

1. Planning

2. Field Observation

3. Office Works

4. Setting out Works


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1. Planning

Planning is performed to decide

• The methods to be adopted for surveying;

• The resources (instruments & personnel) to be used;

• The control points / stations to be used

The planning operation needs a-priori field visit and this is

known as reconnaissance.


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2. Field Observations

Field observations involves

• Collection of field data by making necessary measurements,

• Recording of observed data in a systematic manner.

Before starting any field observation, the permanent adjustments

of all the instruments need to be checked thoroughly by trained

personnel and if required, it must be adjusted.


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3. Office Work

It involves

• Processing, analyzing and calculation of observed data,

• Preparation of necessary data,

• Making of a plan or map of the area,

• Computation of relevant field parameters as per design for

setting out engineering works at site.


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4. Setting out work

To locate and establish different parameters / dimensions at the site

as per design for further engineering works or for the construction

purposes.


Error in Measurements

Surveying is based on measurements and whenever we take measurements,

say of a length or of an angle, we make errors. These errors are due to

(i) Natural causes (ii) Instrumental imperfections and (iii) Personal

Limitations.

Examples of natural causes are variation in speed of wind, temperature and

magnetic declination. A tape or chain which is normally of 30 m length does

not remain so if the temperature changes and as a result error in the

measurement of length occurs. However sophisticated an instrument may be,

it is never perfect. Finally there are limitations of the human senses of sight

and touch. However much we , may try it is difficult to bisect exactly a rod

while taking measurements of an angle.


Types of Errors

Very broadly errors are of two types;

1. Systematic or cumulative.

2. Accidental, random or compensating.

Systematic errors can always be corrected because their magnitude

and sign can both be determined. For example. if a chain is of

standard length under a particular pull and temperature and if the

pull or temperature changes. we can compute its effect on the

length of the chain. i.e. whether it will increase or decrease and by

how much and then apply suitable corrections.


Systematic or cumulative.

Systematic errors can always be corrected because their

magnitude and sign can both be determined. For example. if

a chain is of standard length under a particular pull and

temperature and if the pull or temperature changes. we can

compute its effect on the length of the chain. i.e. whether it

will increase or decrease and by how much and then apply

suitable corrections.


Accidental, random or compensating

Accidental. random or compensating errors are subject to chance

and hence follow the laws of probability. The magnitude and sign

of errors are not definitely known. They are sometimes positive.

sometimes negative, sometimes of small magnitude. sometimes of

large magnitude and hence cannot be computed or eliminated.

However, by taking a large number of observations we can make

an estimate of magnitude of the error likely to be involved.


Accuracy and Precision of Measurements

Accuracy refers to how close a measurement is to the true

value where as Precision is how consistent results are when

measurements are repeated. Precise values differ from each

other because of random error, which is a form of

observational error.


Engr.Shams Ul Islam ([email protected])