Division Of Surveying

Introduction

• The approximate shape of the earth can best be defined as

an oblate tri-axial ovaloid. But, most of the civil engineering

works, concern only with a small portion of the earth which

seems to be a plane surface. Thus, based upon the

consideration of the shape of the earth, surveying is broadly

divided into two types.

• Plane Surveying

• Geodetic Surveying

Scope and Use of Plane surveying

• Plane surveys are carried out of engineering projects on

sufficiently large scale to determine relative positions

of individual features of the earth surface.

• Plane surveys are used for the layout of highways,

railways, canals, fixing boundary pillars, construction

of bridges, factories etc.

• The scope and use of plane surveys is very wide.

Division of Plane Surveying

• Plane surveying can be divided in the following ways.

• Chain Surveying

• Traverse Surveying

• Plane Tabel Surveying

• Ordinary Leveling

Chain Surveying

• Chain surveying is the simplex type of

surveying in which the area to be surveyed is

divided into a number of triangles. The length

of the sides are measured and the interior

details are recorded. The whole area is then

plotted on a suitable scale to produce a map.

Chain Surveying

Traverse Surveying

• Traverse surveying is a type of surveying in

which the plot of land to be surveyed is enclosed

by a series of straight lines making angles with

one another. The length of the lines and the angles

are measured and plotted with all interior details

on a drawing sheet to a suitable scale to produce a

map.

Diagram of an open traverse

Diagram of a closed traverse

Plane Table Surveying

• Plane table is a graphical method of surveying

in which the field works and the plotting is

done simultaneously. It is particularly adopting

in small mapping. Plane table surveying is

used for locating the field computation of area

of field.

Plane Table Surveying

Merits• It is most suitable for preparing small scale map or surveying small

area.

• It is most rapid method.

• Field book is not necessary.

• No great skill is required for satisfactory map.

• It is particularly suitable for magnetic area where prismatic compass

is not reliable.

• Contour and irregular object may be represented accurately.

• It is less costly.

Demerits

• Plane Table Essentially a tropical instruments.

• It is not suitable to work in wet climate.

• There are several accessories to be carried out and therefore they are likely to be lost.

• It is not suitable for accurate work.

Geodetic Surveying

• Geodetic surveying measures all elevations from a

level surface, and because all instruments use a straight

reference plane, this requires all instrument readings of

elevation to be adjust for the curvature of the earth.

Geodetic surveys are used when a high degree of

accuracy is needed and when the survey will cover long

distances or a large area.

Use of Geodetic Surveying :

• Engineering purposes: The engineers uses Geodetic Surveying for finding out the exact location of the concerned point or area. Latitudes and longitudes are needed for any engineering constructions.

• Construction purposes: The builders used Geodetic Surveying for finding out the direction of the buildings or their exact location for vaastu shastra.

• Land Surveying and assessment: The vertical elevation and the horzontal attributes , the latitude and longitudes of the area surveyed are found out through Geodetic Surveying .

The End

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