Division of Surveying:

The approximate shape of the earth can best be defined as an oblate tri-axial ovaloid. But, most of the civil engineering works, concern only with a small portion of the earth which seems to be a plane surface. Thus, based upon the consideration of the shape of the earth, surveying is broadly divided into two types:

Geodetic Surveying- 
In this branch of surveying, the true shape of the earth is taken into consideration. This type of surveying is being carried out for highly precise work and is adopted for surveying of  large area.

Plane-Surveying-  

In this method of surveying, the mean surface of the earth is considered to be a plane surface. This type of survey is applicable for small area (less than 200 square kilometer). Thus for most of the Civil Engineering projects, methods of plane surveying is valid.

Fundamentals assumptions in Plane Surveying: 

All distances and directions are horizontal;   

The direction of the plumb line is same at all points within the limits of the survey; 

All angles (both horizontal and vertical) are plane angles; 

Elevations are with reference to a datum.





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