Survey and its classification

 SURVEY AND IT'S CLASSIFICATIONS

Survey is an art to determine the relative position between points by direct and indirect measurements of distance, direction, and elevation of linear and angular measurement. 

For a surveyor, it is essential for him to know about something Physics, Mathematices, Astronomy. He should also introduced with instruments which is used in surveying.

There are also a term related which named as Levelling.

Levelling is a branch of surveying by which is to establish the elevation of a point and give elevation related to a datum[It is a information obtained from survey].

Survey is the heart of Civil Engineering. It is a very important in Irrigation, Dock and Harbour Engineering and many other field. 

To understand in simple language:-

If there is work process or concreting of a building roof or slab and we are standing there and observe that what is going on. It is also known as Surveying.

There is a great differences between Surveying and Levelling i.e.

Surveying deals with all types of measuremens and planes[vertical or horizontal] but Levelling deals with only vertical planes.

For a civil engineer, it is essential to know about earth and it's surface a little.

The shape of Earth is Oblate Spheroid or Geoid. It is not perfect shape or sphere. 

Approximate diameter of earth is 12740 km that's why radius will 6370 km .

Purpose and Use of Survey:-

1. To determine the relative positions of different objects.

2. To determine angular and linear measurement of different object.

3. To prepare different types of map based on collected information from above points.

There are different types of Map which is prepared by collected information which is as follow:-

1. Topographical map:- The map which show the natural features like mountain, hills, lakes, valley, etc.

2. Cadastral map:- The map which show the boundary of a  location based on datum.

3. Engineer's map:- The map which show the engineer work like harbour, dam, bridge, roads, railway, etc.

4. Military map:- The map which show the military operations and opposing force.

5. Geological map:- The map which show the natural features of a particular area. for e.g. minerals, ground water, petroleum, etc.

6. Archaeological map:- The map which show the map of that place where ancient history done. This map used to research the history.

7. Contour map:- The map show the map consist the contour lines.         Basically, the contour line is used to locate the vertical lines.

CLASSIFICATION OF SURVEYING

There are two types of surveying which is as:

1. Primary survey:- It is of two types 

a. Plane survey  and   b. Geodetic survey

2. Secondary Survey:- It is of many types :

based on instrument used :

Chain survey ,  Theodolite survey ,  Tacheomatric survey ,  Plane table survey ,  Compass survey.

based on method : 

Traversing survey, Triangulation survey.

based on field condition:

Land survey: Topographical survey, Cadastral survey , City survey.

Marine/Hydrograhical/Bathymatric survey

Astronomical survey.

based on object :

Mine survey, Military survey, Engineer survey, Archeological survey, Geological survey. 

Now , we are going to define Primary survey :

1. Plane survey:-   It is the survey in which curvature of earth surface is neglected that's means that surface of earth is assumed to be plane. In other words, The survey in which the surface of earth is taken into account.

                              There are many features of this types of  survey :

A. It is applicable for those area which is less than 250 sq. km.

B.It work with normal instrument like theodolite, compass, chain, measuring tape and other instrument.

C. It's degree of accuracy is low. [because we know that surface of earth is curved ]

2. Geodetic survey:- It is survey in which curvature of earth surface is not neglected that's means that surface of earth is assumed to be curved.

                   In other words, It is that type of survey in which curvature of earth surface is taken into account. There are many features :

1. It is applicable for those area which is more than 250 sq. km.

2. It's degree of accuracy is high.

3. It work with more precise instrument with like GPS[global positioning system], EDM[electronic digital machine]

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