Fun in Surveying

Level Line→is a curved line in a level surface all points of which are normal to the direction of gravity and equidistant from the center of the earth.

Horizontal Surface→it is a plane that is tangent to a level surface at a particular point. It is also perpendicular to the plumb line at the same point.

Horizontal Line→a straight line in a horizontal plane which is tangent to a level line at one point. This line is perpendicular to the direction of gravity at the point of tangency.

Vertical Line→at any point is a line parallel to the direction of gravity.

Mean Sea Level→is an imaginary surface of the sea which is midway between high and low tides. It is taken as the reference surface to which most ground elevations are referred.

Datum→is any convenient level surface coincident or parallel with mean sea level to which elevations of a particular area are referred.

Elevation→the vertical distance above or below mean sea level or any other selected datum.

Difference in Elevation→the vertical distance between the two level surfaces in which the points lie.