ح�م�ن� الر� �ه� الل � م �س� ب

� ح�يم الر� SURVEYING & LEVELLING

Name: Muhammad Sajid Nazir

Roll No.: 2005-CE-38

Before starting our presentation on “Principles of Surveying”, we should be familiar with following terms,

i. Survey:

It is an operation of representing the general features of the land and then producing(representing on a map).

ii. Surveying:

It is a knowledge and technique by which we take measurements on surface to produce a map and vice versa.

iii. Topographical Surveys:

Topographical surveys are used for determining the natural features of country i.e. hills, valleys, rivers, lakes, woods, etc., and also the artificial features i.e. roads, railways, canals, buildings, towns,

villages, etc.

PRICIPLES OF SURVEYING

There are two fundamental principles upon which various survey methods are based, these are:

i. To work from whole to the partii. To fix the positions of new stations by at least two methods

i. TO WORK FROM WHOLE TO THE PART:

The first step in extensive surveys such as town or topographical surveys, is to establish a system of control points with high precision.For horizontal control the points are established by triangulation(by making a triangles) or by precise traversing(by making polygons).To do this by triangulation, the area to be surveyed is divided into large triangles which are surveyed with the greatest accuracy.They are further divided into small triangles which are surveyed with less accuracy.The object of this system of working is to prevent the accumulation of error and to control the localize minor errors.On the other hand if we work from part to the whole, small errors are magnified in the process of expansion and become uncontrollable at the end.Thus in this method of surveying by chain angles, the surveyor fixes the position of the part of a line Bb in the figure 1 below,

Figure 1

and from that he finds the direction of the whole line BC.This method is opposed to the above principle and should be used only in exceptional circumstances.

ii. TO FIX THE POSITIONS OF NEW STATIONS AT LEAST BY TWO METHODS:

The new stations are fixed from points already fixed by, i. Linear Measurementii.Angular Measurementiii.Both Linear and Angular Measurements