Chain surveying can be defined as the method of surveying the land area by dividing the area into triangles. Hence the principle of chain surveying is TRIANGULATION. The triangles developed must be WELLCONDITIONED TRIANGLES.
In chain surveying, a CHAIN or a TAPE is used to measure the sides of the triangles. Along with this ANGULAR MEASUREMENTS are also taken. The accuracy of chain surveying is controlled by the LINES & CHECK LINES.
Point to Remember: If the three sides of the triangle are known, there is no need to determine the angle of inclinations of the triangles.
Principle of Chain Surveying
The principles of chain surveying are:
 The whole area that needs to be surveyed is divided into a skeleton of a framework that consists of a number of wellconnected networks of wellconditioned triangles. This is the principle of Triangulation.
 The details are located with respect to the sides of a triangle or any subsidiary lines that is running between the sides by taking lateral measurements called offsets.
Chain Surveying Suitability & Unsuitability
SUITABILITY

UNSUITABILITY

More or
less leveled ground surface

Crowded
Area

Area of
surveying is small

Area
with too many undulations

Preparation
of smallscale map

Area is
very large

Wellconditioned the triangle can be formed easily

Difficulty
in the formation of wellconditioned triangles

LargeScale and SmallScale Maps
A map is said to be a large scale when 1cm of the map represents a small distance. Say,
1cm = 1m, i.e. RF = 1/100;
A map is said to be a small scale when 1cm of the map represents a smallscale map.
1cm = 100m; i.e. RF = 1/10000;
Points to Remember: A map with RF value less than 1/500 is called as LARGESCALE MAPS & a map with RF value greater than 1/500 is called as SMALLSCALE MAPS.
WellConditioned Triangles and IllConditioned Triangles
The triangles with angle(A) in the range 30<A<120 is called as WELLCONDITIONED TRIANGLES. An equilateral triangle is the best wellconditioned triangle (Ideal Triangle) possible.
The wellconditioned triangle has perfect apex points that are sharp and are located by single ‘dot’. This will bring no possibility of relative displacement of the plotted point.
An illconditioned triangle is a triangle with an internal angle (A) in the range 120<A<30.
Points to Remember: Chain Surveying does not employ illconditioned triangles. These triangles have no perfect apex points which are neither sharp nor welldefined. Any slight displacement results in large errors in plotting.
Read More:
 What is Principle of Surveying?
 What is Chain Surveying?
 Reconnaissance Survey and Index Sketch in Chain Surveying
 Linear Measurements in Surveying
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