Engineering Surveying

Engineering Surveying Exam 2015

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Terms in Levelling
 Level surface
The surface which is parallel to the mean spheroid surface of the earth is known as Level Surface.
A surface over which water will not flow (equipotential)
The direction of gravity is always normal to a level surface

 Horizontal surface

 A surface tangential to the level surface as any point is known as horizontal surface.

 Horizontal line

 A line lying on the horizontal surface , is known as the horizontal line.

 Vertical line

The direction indicated by the direction of gravity is known as the vertical line.

 Vertical plane

A plane containing vertical line is a Vertical plane.

 V.Datum

A reference surface to which all the heights of the points were referred

Can be arbitrary or a National height datum

In Sri Lanka we use MSL as the National Datum for heights

The surface which defines the MSL is Mean Sea  Level