Skip to main content

Correction due to curvature and refraction AND combined correction in surveying

In geodetic surveying, error due to curvature and refraction is taken into action when the area is greater than 256 km²

 Correction due to curvature (Cc)
           Error due to curvature is taken into action because during leveling with theodolite  or Autolevel the horizontal line and level line do not coincide. Level line is curved line parallel to the earth surface and horizontal line is straight line.

             this correction is given by Cc =0.07849d² OR 0.0785d²
                                                                here, d is the linear distance (in km)
  Correction due to refraction (Cr)
           Error due to refraction is taken into action due to the changing of medium of light either from a denser medium to lightier medium or viceversa.
                   it is 1/7 of correction due to curvature 
                                                  it is equals to 0.112d²
  Combined correction due to curvature and refraction (C)
             it is the sum of both the corrections (correction due to curvature and correction due to refraction).
                      it is 6/7 of correction due to curvature
                               C= 6/7x(0.785d²)
                                  = -0.6728d²
            NOTE- d is in kilometres and the answer obtained is in metres.

                            THANKS FOR YOUR KIND VISIT


Popular posts from this blog

Prestressed concrete

The basic concept of prestresssing the concrete consists in introducing the artificially the compressive stresses in a structure before it is loaded. The tensile stresses in the prestressed concrete structure may be reduced to a great extent or even entirely eliniminated depending upon the magnitude of prestressing. In a prestressed concrete structure, the cost of supporting structure and foundation is reduced, dead load of structure is reduced and cracking of concrete is avoided. The high strength concrete and high tensile steel should be used in a prestressed concrete member. According to Indian standards, the cube strength of the concrete used should bot be less  than 35N/mm 2 . The ultimate strength of high tensile steel wires used in prestressing varies from 1500N/mm 2 for 8mm diameter bars to 2350N/mm 2 for 1.5 mm diameter bars. The various methods adopted in prestresssing are as follows: Pre-tensioning The method of providing desired amount of compressive stress in

Structure of tree

Tree basically consist of three parts i.e. trunk, crown, and roots. Function of trunk is to support the crown and to supply water and nutrients from the roots to the devices through branches and from leaves to the roots. Further subdivided in two parts: 1) macrostructure The structure of wood , visible to naked eye or at a small magnification is called the macrostructure. a) Pitch Inner molt, central position or core of the tree is called the pitch or medullar Vary in size and change for different trees b) Heart wood Inner annual rings surrounding the pitch constitute heart wood Dark in colour and imparts rigidity to the tree c) Sap wood Outer annual rings between Heartwood and cambium layer is known as sapwood It is light in weight and colour d) Cambium layer Thin layer of sap between  sapwood and inner bark is known as cambium layer If the bark is removed for any reason, then the surface of exposed and cells cease to be inactive resulting in the