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LECTURE №1


                                   THE BASIC SURVEYING METHODS



                      1.1 Introduction
                      Most  surveying  activities  are  performed  under  the  pseudo  assumption  that
                  measurements  are  being  made  with  reference  to  a  flat  horizontal  surface.  This
                  requires some further explanation.
                      The  earth  actually  has  the  approximate  shape  of  a  spheroid  that  is  the  solid
                  generated by an ellipse rotated on its minor axis. However, for our purposes, we
                  can consider the earth to be a perfect sphere with a constant diameter. In addition,
                  we can consider that the average level of the ocean or mean sea levels represent the
                  surface of sphere.

























                                                     Fig. 1.1 Shape of the earth

                      By  definition,  the  curved  surface  of  a  sphere  is  termed  a  level  surface.  The
                  direction of gravity is perpendicular to this level surface at all points, and gravity is
                  used  as  a  reference  direction  for  all  surveying  measurements.  The  vertical
                  direction is taken to be the direction of gravity. In addition, the horizontal direction
                  is the direction perpendicular to the vertical direction of gravity.












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