CLASSIFICATION OF SURVEYING - FUNCTIONAL AND INSTRUMENT BASED SURVEYING CLASSIFICATION (StudyCivilEngg.com)

CLASSIFICATION OF SURVEYING

SUBJECT : SURVEYING

FUNCTIONAL CLASSIFICATION OF SURVEYING

Based on the purpose for which they are conducted, surveys may be classified into following types -

CONTROL SURVEYING

It consists of establishing the horizontal and vertical positions of widely  spaced control points using the principles of geodetic surveying. In India, control surveying is done  by the Survey of India.

LAND SURVEYING

Land surveys are conducted to determine the boundaries and areas of tracts of  land. These are the oldest types, as land surveys have been used since the early civilisation. These are  also known as property surveys, boundary surveys or cadastral surveys. These surveys are also used  to provide data for making a plan of the area.  Land surveying is the most common type of surveying. The methods of plane surveying are used for  locating property lines, subdividing land into small plots and determining the areas for the transfer of  land from one owner to the other. A cadastral survey is done for marking legal boundaries of land.  

CITY SURVEYING

These surveys are conducted within the limits of a city for urban planning. These  are required for the purpose of layout of streets, buildings, sewers, pipes, etc.  

TOPOGRAPHICAL SURVEYING

Topography is defined as the shape or configuration of the earth’s  surface. The topographic maps show not only the plan but also the elevations of the terrain.  These surveys are required to establish horizontal locations of the various points as well as the vertical locations. Information pertaining to reliefs and undulations on the earth’s surface is generally  shown in the form of contours of equal elevations.  Cartography is the science of expressing graphically the knowledge of the earth’s surface and its varied features. Cartographic surveying includes all the operations leading to the production of  topographic maps.

ROUTE SURVEYING

These surveys are special types of topographical surveys conducted along a  proposed route for a highway, railway, sewer line, etc. The route survey is done along a wide strip.  In general, the route surveying also includes the staking out and calculations of the earth work.  

MINE SURVEYING

These surveys are conducted to determine the relative positions and elevations of  mines, shafts, adits, bore holes, etc. for underground works.  In general, mine surveys include both underground surveys and the related surface surveys.  Mine surveys are used to plan the working of mines and to compute the volume of material in  mines.

HYDROGRAPHIC SURVEYING

These surveys are conducted on or near the body of water, such as lakes,  rivers, bays, harbours, Marine surveys are special type of hydrographic surveys. These cover a broader  area near sea for offshore structures, navigations, and tides, etc.  The hydrographic surveys consists of locating shore lines, estimation of water flow, and  determination of the shape of areas beneath the water surface. It also includes the determination of  channel depth, location of locks, sand bars, buoys, etc.  

ENGINEERING SURVEYING

Engineering surveys are conducted to collect data for the designing and  planning of engineering works such as building, roads, bridges, dams, reservoirs, sewers, and water  supply lines.  These surveys generally include land surveys, city surveys, topographical surveys and route surveys  discussed above.  

ASTRONOMIC SURVEYING

These surveys are conducted for the determination of latitudes, longitudes,  azimuths, local time, etc. for various places on the earth by observing heavenly bodies (the sun or  stars). The absolute locations of various points on the earth is obtained by astronomic surveys.  

SATELLITE SURVEYING

These surveys are conducted to obtain intercontinental, inter-datum and  inter-island geodetic ties all the world over by artificial earth satellites. These surveys are done by  space agencies.

GEOLOGICAL SURVEYING

Geological surveys are conducted to obtain information about different  strata of earth’s surface for geological studies. Geological maps are prepared depicting the details of  the strata.  

CONSTRUCTION SURVEYING

All the above mentioned surveys are conducted to obtain information  required for preparation of maps, plans, sections, etc. After the plans have been prepared and the  structures designed, the construction surveys is conducted. The points and lines are established on  the ground, and the layout plan of the structure is marked on the ground. Stakes are driven for  setting out. Thus construction surveys are the reverse of engineering surveys.  Construction surveys are also called location surveys or setting out.  

MISCELLANEOUS SURVEYING

• Archaeological surveying - These are done to unearth relics of antiquity.  
• Military surveying - These are conducted to determine the routes and points of strategic  importance.  
• Gravity surveys. These are conducted to measure the intensity of the gravitational force at  various points.  
• General surveying - These are used to acquire and accumulate qualitative information and  quantitative data for a specific purpose by observing, counting, classifying and recording  according to the need. For example, soil surveying and traffic surveying

CLASSIFICATION BASED ON THE INSTRUMENTS USED

Based on the instruments used, the surveys can be classified as under

CHAIN SURVEYING

This is the simplest type of surveying in which only linear measurements  are taken with a chain or a tape. Angular measurements are not taken.  Chain surveying is generally used when high accuracy is not required.  

COMPASS SURVEYING

In compass surveying, the horizontal angles are measured with the help  of a magnetic compass, in addition to the linear measurements with a chain or a tape.  As a magnetic compass is not a precise angle-measuring instrument, the compass survey is not  very accurate. However, it is more accurate than a chain survey.  

LEVELLING

This is a type of survey in which a levelling instrument is used for determination of  relative elevations (levels) of various points in the vertical plane.  In surveying, the vertical line means the direction of gravity indicated by a plumb bob. The plane  containing the vertical line is a vertical plane. The horizontal direction is the direction perpendicular  to the gravity.  Levelling is used for finding out the difference in elevations and for finding out the elevations  with respect to some reference plane (datum). Levelling is extremely important in most of the  engineering works. It is required for preparation of topographical maps and for the control of  elevations during construction.  

PLANE TABLE SURVEYING

In plane table surveys, a map is prepared in the field while viewing the  terrain after determining the directions of various lines and taking the linear measurements with a  chain or a tape.  The accuracy of the plane table survey is low. Its main advantage is that the measurements and  plottings are done simultaneously in the field. 

THEODOLITE SURVEYING

A theodolite is a very precise instrument for measuring horizontal and  vertical angles.  The theodolite surveys can be broadly classified into two. types: (i) Traverse, (ii) Triangulation. In a  traverse, the various stations form a polygon. The horizontal angles are measured with a theodolite,  whereas the linear measurements are made with a tape. In triangulation, the lines form a system of  triangles. The base line is measured accurately and the lengths of all other lines are computed from the  measured angles. Triangulation is used for establishing control points over extensive areas. Theodolite  surveys are quite accurate.  

TACHEOMETRIC SURVEYING

A Tacheometer is a special type of theodolite which is fitted with a  stadia diaphragm having two horizontal cross hairs in addition to the central horizontal hair. In  Tacheometric surveying, horizontal angles, horizontal distances and elevations are measured with  a Tacheometer.  Although Tacheometric surveys are not very accurate, these are extremely convenient for determining  topographical details.  

PHOTOGRAMMETRIC SURVEYING

Photogrammetry is the science of taking measurements with the  help of photographs. Photogrammetric surveys are generally used for topographic mapping of vast  areas. These are extremely useful for obtaining topographical details of areas which are difficult to  reach.  Photographs are generally taken from an aeroplane. However, for certain areas where suitable sites  exist, photographs can be taken from ground-based cameras.  

EDM SURVEYING

Trilateration is a type of triangulation in which all the three sides of each triangle  are measured accurately with EDM instruments. The angles are computed indirectly from the known  sides of the triangles. Thus all the sides and angles are determined.  Like triangulation, trilateration is also used for fixing the position of control points. With the  availability of modern EDM instruments, the trilateration is more convenient than the triangulation  and is gradually replacing the later for control surveys

RELATED POSTS

• PRIMARY DIVISIONS OF SURVEYING
• INTRODUCTION & HISTORY OF SURVEYING