Surveying is the practice of measuring and mapping the Earth's surface to determine the relative positions of points and distances between them. Used in construction, land development, and mapping, it employs various instruments and techniques, ensuring accurate spatial data for engineering, geographic analysis, and infrastructure planning. The knowledge of surveying is very important and advantageous in many phases of engineering. The earliest surveys were made in connection with land surveys only, but with the advancement in technology, in every engineering project such as water supply and irrigation schemes, railways, highways, bridges, mines and transmission lines, surveying is being employed. 

• The object of surveying in civil engineering is to prepare a plan or map so that it may represent the area on a horizontal plane. Before plans and estimates are prepared, boundaries should be determined and the topography of the site is ascertained using a surveying process. 

This article will be going to include the topic Surveying in civil engineering along with their classifications, objectives, principles and uses. This article will provide you with all the information required to ace various competitive examinations like SSC JE CE, RRB JE and GATE CE.

What is Surveying in Civil Engineering?

Surveying is the art of determining the relative positions of points on, above or beneath the surface of the earth by means of direct or indirect measurements of distance, direction and elevation. The process of surveying also includes representations of all results on a sheet of paper known as a plan or map. The application of surveying requires skill as well as the knowledge of mathematics, physics and astronomy to some extent.

Civil surveying is a necessary process in engineering that involves measuring and mapping the details of a land area. These measurements are essential for planning and designing construction projects. The primary goal of surveying in civil engineering is to understand the three-dimensional positions of various points on the land, helping to create accurate plans and layouts for future developments.

Objectives of Surveying in Civil Engineering

The main objectives of surveying in civil engineering are as summarized below:

• To determine the relative position of any objects or points on the earth. 
• To determine the distance and angles between various objects. 
• To prepare a map or plan to represent an area on a horizontal plane.
• To define control points and boundaries of an area, for example, a cadastral survey. 

Principle of Surveying

The fundamental principles of surveying which are the various methods of surveying are based are of two aspects, as follows:

1. Working from whole to part
2. Location of a point by measurement from two points of reference

Working from Whole to Part

It is essential to establish a system of control points and fix them with greater accuracy. Less precise methods can then establish minor control points, and the details can be located using these minor control points by minor traverses. The idea behind this principle is to prevent the accumulation of errors and to control and localise minor errors that would expand to greater magnitudes.

Location of a Point by Measurement from Two Points of Reference

The relative positions of the points to be surveyed should be located by measurement from at least two points of reference, the positions of which have already been fixed. 

• Fig (a): Distances PQ and QR can be measured, and point R can be plotted by swinging the arcs to the same scale to which PQ has been plotted. This principle is mostly used in Chain surveying.
• Fig (b): A perpendicular RS can be dropped on the reference line PQ and lengths PS and SR are measured. The point R can then be plotted using a set square. This principle is used for defining details.
• Fig (c): The distance QR and the angle PQR can be measured, and point R is plotted either by means of a protractor or trigonometrically. This method is used in traversing. 
• Fig (d): In this method, the distance PR and QR are not measured, but the (angle) RPQ and (angle) RQP are measured. Knowing the distance PQ, point R is plotted by means of a protractor. This type of method is useful in triangulation. 
• Fig (e): (angle) RQP and distance PR are measured, and point R is plotted either by protracting an angle and swinging an arc from P or plotted trigonometrically. This method is also used in traversing.