What is Surveying in Civil Engineering?

Surveying is the practice to determine the relative three-dimensional positions of various points on the earth’s surface. This is done by computing the vertical and horizontal distances, angles between the points, collecting the observations, and plotting them on a map of any appropriate scale. Accuracy can be achieved by using the latest instruments like a theodolite, tachometer, etc. Leveling is a subdivision of surveying where the objective is to locate the elevation of objects considering a datum level.

Before starting any major construction project, the surveyor needs to carry out surveying to understand the site topography, availability of natural resources, network triangulation, and property boundaries.

History

From the first past-built large structures by humans, surveying was incorporated. It is the need for the planning and execution of almost every form of construction. In the ancient era of Egypt, for re-location of the boundaries after the floods in the Nile River annually, land surveyors used rope stretcher instruments. The Romans considered surveying as a profession by taking basic dimensions using measuring tools like invar tapes through which the divisions of the roman empire were held. It was also practiced in Europe and England, but the advancement and transformation in the methods of surveying were carried out according to the needs.

Fundamental principles of surveying

Detection of a point by the measurement of the given two points of reference

According to this principle, the relative position of one point to be surveyed should be located and measured from at least two points of reference which have fixed positions previously.

Working from whole to part

According to this principle, it is always recommended to carry out survey work from whole to part. That is, when any area needs to be surveyed, first a control points system is to be established covering the whole area with high perfection followed by the minor details located almost roughly. This shall prevent the accumulation of errors and would expand to greater magnitudes. If not followed, it makes the task uncontrollable.

Primary methods of surveying

Plane surveying method

Plane surveying is the one in which the earth’s surface is considered as a plane and the earth’s curvature is ignored. In such a type of surveying, a line joining any two stations is considered as a straight line. The triangle formed by joining any three points is considered as a plane triangle and the angles of the triangle are also considered as plain angles. The lengths of the triangle’s sides are measured using Trilateration. A surveyor carries out surveying for small places with less than 250 square kilometer area and also carried out by local or state agencies like Research & Development department, Irrigation department, Railway department, etc.

Geodetic surveying method

Geodetic Surveying is the method in which the earth’s curvature is taken into consideration. It is generally extended over much larger areas. The line that joins any two stations is to be considered a curved line. The triangle formed by any three points is considered to be spherical and the angles of the triangle are also taken into account as spherical angles. Geodetic surveying is conducted by the National Survey and Mapping Organization, Survey of India Department and land surveyors carry out surveying for a larger area exceeding 250 square kilometers.

Other Methods of Surveying

Based on fieldwork

Land Surveying Method 

Land Surveying or Topographical Survey generally deals with measuring natural or artificial features on land such as rivers, lakes, streams, railways, hills, roads, woods, canals, towns, buildings & infrastructure, water supply systems, etc.

Marine Surveying Method 

Marine or hydrographic surveying deals with measuring water bodies for purpose of navigation, water supply, harbor works, or for estimation of mean sea level. The work of a surveyor contains the measurement of discharge of streams, composing topographic survey of shores and banks, identifying soundings to determine the depth of water, and observing the fluctuations of the ocean tide.

Astronomical Surveying Method 

The astronomical survey determines the absolute location of any point or the absolute location and direction of any line on the surface of the earth. This is seen in the observations and the heavenly bodies such as the sun or any fixed star. It is conducted for determining the latitudes, longitudes, azimuths, local time, etc., and for different places on earth by observing heavenly bodies (sun or the stars).

Archaeological Survey Method

Archaeological survey is carried out by the surveyor to gather information regarding the sites that are important from archaeological considerations and for unearthing antique relics, civilization, kingdoms, forts, temples, etc.

Aerial Survey Method

Photographic or Aerial survey collects data about large tracks of land by taking photographs from above by drone instruments or planes having better response rates. It is usually conducted from an aircraft for a better view of measuring distances. Aerial cameras take images of the earth’s surface in overlapping strips pattern of the land.

Based on Object

Geological Surveying Method

It maps out features of the physical landscape, like rivers, valleys, mountains, etc. Satellite data holds ample significance for geological surveying, and engineers seldom use this data or aerial images to help them in their completion of work.

Mine Surveying Method

It includes both surface and underground surveys and is conducted for the exploration of mineral deposits and to guide tunneling along with other operations associated with mining.

Military surveying Method

It holds a lot of significance and critical applications in the military. Aerial surveys are conducted and it is conducted to locate strategic positions and enemy locations for the objective of army operations.

Based on Instruments used

Chain and Compass surveying Method

In this survey linear measurements joining, control points are made with a chain or a tape and the angles, as well as right angles, are measured with the help of a magnetic compass instrument.

Plane table surveying Method

It is a graphical method of surveying where the fieldwork and plotting of locations are done simultaneously.

Theodolite surveying Method

In theodolite survey, the horizontal angles are observed with an alidade and measured with the theodolite instrument with more precision than a compass and the linear dimensions are taken with chains or tapes.

Tachometric surveying Method

Tachometer instrument is a special theodolite type survey instrument and is used to determine horizontal and vertical distances indirectly.

Based on Methods

Triangulation Surveying Method

The Triangulation method is a basic surveying method and is adopted when the surveyed area is large. The entire area is divided into a triangulation of networks by the surveyor.

Traversing Surveying Method

Traversing is a circuit of survey lines that may be open or closed. When the linear measurements are carried out with a chain and a tape and the directions or horizontal angles are computed with a compass or a theodolite respectively it is called traversing.

Innovations and technology

Surveying and land survey techniques are required in various fields like the positioning of earthwork structures, provision of maps with details of specified locations, measuring the distance between two distinct points, etc. Surveying requires GPS data from satellites that have high-precision electromechanical and optical instruments which are required for ensuring that the measurements are having accuracy.

Computer-Aided Drawing (CAD)

Once the engineers have collected survey data, computer-aided drafting helps turn that data into a clear visual representation, like a map or any three-dimensional model. It permits for a greater level of perfection and details faster which could not be achieved with manual sketching.

Global satellite data positioning

GPS data is significant for civil surveying since it allows for pointing the exact locations and coordinates by control networks. Where a visual assessment would not be sufficient for telling whether an object had shifted or a sunk foundation, the accuracy of GPS data allows engineers to know for sure. Trilateration is used in Global Positioning System (GPS) to locate the user’s position, elevation and speed.

Point cloud modeling 

To develop and prepare 3D survey models with accuracy, engineers also often create a point cloud or a set of three-dimensional data points. the surveyor uses 3D laser-scanning technology for the generation of a data map of the area they wish to model. Once they have data that represents every surface they need, they can then bring the marked points together through point cloud modeling into a précised and detailed 3D model.

Context and Applications

The topic is taught in courses such as:

• Bachelors in Technology (Engineering)
• Bachelors in Technology (Civil Engineering)
• Bachelors in Technology (Remote Sensing)
• Masters in Science (Geospatial Systems Engineering)

Practice Problems

1. The Romans took basic dimensions using which measuring tools were used for the division of their empire?

1. Rope Stretcher
2. Invar Tapes
3. Measuring Tape
4. Scale

Correct option- b

Explanation: The Romans took basic dimensions using invar tapes as measuring tools that were used for the division of their empire.

2. Which of them is/are a fundamental principle(s) of Surveying?

1. Detection of a point by the measurement of the given two points of reference
2. Working from whole to part
3. Both a. and b.
4. None of the above

Correct option: c

Explanation: Detection of a point by the measurement of the given two points of reference and working from whole to part is the fundamental principle of Surveying.

3. Which Surveying Method is used for an area exceeding 250 square kilometers?

1. Geodetic Surveying Method
2. Plane Surveying Method
3. Land Surveying Method
4. Marine Surveying Method

Correct option: a

Explanation: Geodetic Surveying Method is used for an area exceeding 250 square kilometers.

4. Which Surveying Method is used based on Instruments?

1. Military Surveying Method
2. Triangulation Surveying Method
3. Archaeological Surveying Method
4. Theodolite Surveying Method

Correct option: d

Explanation: Theodolite Surveying Method is used based on Instruments.

5. What is the full form of GPS?

1. Global Passing System
2. Global Positioning System
3. Grand Passing System
4. Grand Positioning System

Correct option- b

Explanation: Global Positioning System is the full-form of GPS.

Related Concepts

• Geographic Information Systems
• Spatial Computing
• Construction
• Civil Engineering
• Mapping and Remote Sensing