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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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