Principle of Plane Tabling:

The principle of plane tabling is a simple technique used for mapping the land surface. In this technique, a plane table is set up on a tripod at a station point, and the table is leveled accurately. The surveyor then observes the features of the land and records them directly on the table. The following are the principles of plane tabling.

Parallelism:

The first principle of plane tabling is parallelism. The table should be set up parallel to the plane of the ground surface. This is achieved by adjusting the height of the tripod legs until the table is level. This ensures that the observations made on the table are accurate and correspond to the features of the ground.

Triangulation:

The second principle of plane tabling is triangulation. The surveyor should measure the distance between the station point and at least two other points on the ground. This can be accomplished using a tape measure or by pacing out the distance. Then, the surveyor should measure the angles between the station point and the two other points using a theodolite. This creates a triangle, and the surveyor can use trigonometry to calculate the direction and distance of other features on the ground.

Traversing:

The third principle of plane tabling is traversing. The surveyor should measure the distance and direction of a series of points on the ground, creating a traverse. This can be accomplished using a tape measure or by pacing out the distance. Then, the surveyor should measure the angles between each point using a theodolite. This allows the surveyor to map the ground surface accurately.

Centering:

The fourth principle of plane tabling is centering. The surveyor should ensure that the station point is accurately located on the table. This is achieved by using a plumb bob to mark the center of the table, and then aligning the table with the station point. This ensures that the observations made on the table correspond to the features of the ground.

In conclusion, the principles of plane tabling are parallelism, triangulation, traversing, and centering. These principles ensure that the surveyor can accurately map the features of the ground surface.