What is the Survey of civil engineering?
Surveying is the art of determining the relative position of distinctive features on, above or beneath the surface of the earth by means of measurement of distance, direction, and elevation. The survey of civil engineering is to know the present condition of the surface on the earth and what kinds of activities we should do to get the required condition of the surface. Like, how much cutting and filling will be required to get a smooth surface along 10 kilometers of road.
Objective / Importance of surveying
- The main objective of surveying is the presentation of plans and maps of the areas to show the relative positions of the objectives on the surface of the earth.
- The science of surveying has been developing since the very initial stage of human civilization as per their requirements. They evolved methods for demarcating their boundaries as soon as they developed a sense of land property.
- Due to innovation in technology, the science of surveying has attained its due importance and the practical importance of surveying cannot be over-estimated.
- Surveying is the first step for the execution of any projects. An engineer must be thoroughly familiar with the principles and different methods of surveying mapping because the success of any engineering project is based on the accurate and complete survey works.
Uses of surveying
- To prepare the topographical maps, which shows the hills, valleys, rivers, villages, towns, forests, etc of a country.
- To prepare the cadastral maps showing the boundaries of fields, houses, and other properties.
- To prepare the engineering maps which show the deals of engineering works such as roads, railways, reservoirs, irrigation canals, etc.
- To prepare the military maps showing the roads and railway communication with different parts of a country. Such maps also show the different strategic points important for the defense of a country.
- To prepare a counter map to determine the capacity of a reservoir, to find the best possible route for roads, railways, etc.
- To prepare a geological map showing the areas including underground resources.
- To prepare archeological maps including places where ancient relics exist.
Primary Division of surveying
The surveying primarily divided into two divisions:
- Plane surveying
- Geodetic surveying
- Plane surveying:- The surveys in which the earth’s surface is assumed as a plane and the curvature of the earth are ignored are known as plane surveys. As the plane survey extends only over small areas, the lines connecting any two points on the surface of the earth, are treated as straight lines and the angles between these lines are taken as plane angles.
- Geodetic Surveying:- The surveys in which curvature of the earth is taken and a higher degree of accuracy in linear as well as angular observations are achieved are known as Geodetic Surveying. In geodetic surveying, the curvature of the earth’s surface is taken into account while making measurements on the earth’s surface. As the surveys extend over large areas, lines connecting any two points on the surface of the earth, are treated as arcs.
According to the use and the purpose of the final amps, surveys may be classified, under the following different heads.
Classification of Surveys
Classification based upon the nature of the field
- Land surveys. The survey carried out on the land for infrastructure like road, railway, etc is known as Land survey.
- Topographic surveys: The surveys which are carried out to depict the topography of the mountainous terrain, rivers, water bodies, wooded areas and other cultural details such as roads, railways, townships, etc. , are called topographical surveys.
- Cadastral Surveys: The surveys which are generally plotted to a larger scale than topographical surveys and arc carried out for fixing the properties lines, calculation of area of landed properties and preparation of revenue maps of states, are called a cadastral survey.
- City Surveys: The surveys which are used for the construction of roads, parks, water supply system and other constructional works for any developing township, are called city surveys.
- Hydrographic surveys: The surveys which deal with the mapping of large water bodies for the purpose of navigation, construction of harbor works, prediction of ties and determination of mean sea level, are called Hydrographic Surveys.
- Astronomical Surveys: The surveys which are carried out for determining absolute locations i.e. latitudes of different places on the earth surface and the direction of any line on the surface of the earth by making observations to heavenly bodies, i.e. stars and sun, are called astronomical surveys.
Classification based on the purpose of the survey
- Engineering Surveys: The surveys which are carried out for the determination of quantities or to afford sufficient data for designing engineering works, such as roads, reservoirs, sewage disposal, water supply, etc are called engineering surveys.
- Military or Defence Surveys: The surveys which are carried out for the preparation of maps of the areas of military importance are called military surveys.
- Mine Surveys: The surveys which are carried out for an exploration of the mineral wealth beneath the surface of the ground, i.e. coal, copper, gold, iron ores, etc. are called Mine Surveys.
- Geological Surveys: The surveys which are carried out for ascertaining the composition of the earth’s crust i.e. different strata of rocks of the earth crust are called Geological Surveys.
- Archeological Surveys: The surveys which are carried out to prepare maps of ancient culture i.e. antiquities are called Archeological Surveys.
Classification of Survey of civil engineering based on the instrument used
According to the instrument used and method of surveying, method surveys may also be classified as under:
- Chain surveying
- Compass surveying
- Plane table surveying
- Theodolite surveying
- Tacheometric surveying
- Triangulation surveying
- Aerial surveying
- Photogrammetric surveying
Basic Principle of Surveying
- Location of a point by measurement from at least two points of reference ( linear or angular measurements ):
The new point should always be fixed at least two measurements ( linear or angular ) from fixed reference points.
- Working from whole to part:
- The whole area is first enclosed by main stations and main survey lines and divided into a number of parts by forming well-conditioned triangles.
- A nearly equilateral triangle is considered to be the best well-conditioned triangle.
- The main survey lines and sides of the triangles are measured very accurately with standard chain or tape.
- The aim of this process is to prevent the accumulation of error and if there is an error in any sides of a triangle, then it will not affect the whole work. The error can always be detected or eliminated.
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