Surveying Basic Definitions
1. Earth Surface:
Earth Surface has a solid and active surface with mountains, valleys, canyons, plains and so much more.
Earth is special because it is an ocean planet.
Water covers 70% of Earth's surface.
2. Level Surface:
A surface parallel to mean spheroid surface of earth is called level surface.
It is a curved surface, every point on which is equidistant from the center of earth and every surface element is normal to the plumb line or line of gravity.
3. Horizontal Plane:
A plane which is tangential to mean level surface of earth at every point is known as horizontal plane.
The level surface is curved while horizontal surface is straight. It’s perpendicular to the plumb line.
4. Vertical line:
The direction indicated by a plumb line (direction of gravity) is known as vertical line.
This line is perpendicular to the horizontal line.
