Principles of Surveying

Principles of Surveying | Objectives of Surveying | Uses of Surveying

 

The first step of any construction work is surveying and thus it is an important branch of civil engineering. Surveying is the art of determining the relative position of various features above, on or beneath the surface of the earth by means of different instruments. Some principles of surveying are explained below.

As per the definition given out by the American Congress on Surveying and Mapping (ACSM), “Surveying is the science and art of making all essential measurements to determine the relative position of points or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points or details”.

Surveying is basically conducted for measuring the linear parameters as well as the angular parameters for establishment of points by means of which the plans and maps can be prepared. It utilizes a wide variety of tools and equipment. Some of the important equipment used in surveying includes theodolite, compass, auto-level, chains and tapes, levelling staff etc.

Surveying is the most important branch of civil engineering before and after all the civil engineering works such as designing and construction of roads, buildings, bridges, irrigation and water supply systems etc. It basically provides the basic framework for the conception, design and the execution of the construction works. The process of surveying includes both the fieldwork and office work. This is because the measurements are taken in the field and the relevant mathematical calculations for the determination of the distances, angles, directions, elevations, locations, areas and volumes are done in the office.

 

Objectives of Surveying

The main objectives of surveying can be listed as follows:

a. To determine the relative position of various points above, on or beneath the surface of the earth.

b. To take the linear measurements and angular measurements between various points.

c. To prepare the plans and maps i.e. for the representation of a measured plot of the area on a horizontal plane.

d. To provide a basis for the civil engineering construction works and activities.

 

Principles of Surveying

In general, Surveying is based upon a number of principles (or guidelines) which can be listed as follows:

a. Working from Whole to Part

b. Location of Point by Measurement from Two Points of Reference

c. Consistency of Work

d. Independent Check

e. Accuracy Required

 

a. Working from Whole to Part

As the name itself implies, the survey work must be carried out from whole to part. This means that when an area is to be surveyed, first of all, a system of control points is established such that it covers the entire area with a higher degree of precision. After this, the minor control points and details are further established with a lesser degree of precision.

The main idea of this principle is to prevent the undue accumulation of errors and thereby control and localize the minor errors.

If the survey is carried out from part to whole, the magnitudes of errors accumulated would be very high.

Example: This principle is essential in International Boundary Locating, Property Boundary  Locating, etc.

 

b. Location of Point by Measurement From Two Points of Reference

On the basis of this principle, the relative position of the desired points to be surveyed must be located by taking the measurement from at least two (preferably three) points of reference, such that the position of the reference points have already been fixed previously.

 

Principles of Surveying

Figure: Location of a Point from Two Reference Points

Let R be the point whose location is to be fixed and P and Q be the two reference points whose positions have already been fixed.

The position of the point R can be determined by any-one of the above-shown methods.

 

c. Consistency of Work

Another important principle of surveying is the consistency of work.

It must be noted that keeping consistency in the method, instrument, reading and noting observations etc helps to gain the desired level of accuracy.

 

d. Independent Check

Independent check is the fundamental principle that is generally adopted to prevent the error in the survey work.

According to this principle, every measurement that is taken in the field must be re-checked by adopting a suitable method of independent field tests and observations so that any mistake if present is not passed without notice.

 

e. Accuracy Required

According to this principle of surveying; the proper method and instrument must be used for the survey work on the basis of the degree of accuracy required.

 

Uses of Surveying

Some of the important uses of surveying can be listed as follows:

a. It is essential for the preparation of the topographical maps indicating the forests, hills and other topographical features of an area.

b. It is vital for the planning, designing and construction of infrastructures such as road, bridges, pipeline systems etc.

c. It is necessary for the preparation of cadastral maps for demarcating the boundaries and property lines.

d. It is also essential for national security planning, military purpose, military strategic planning etc.

e. Mine surveying is vital for the identification and exploration of mines and resources.

f. It is also necessary for the planning and fixing of navigation routes.

 

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