Operations involved in Plane Table Surveying
SETTING UP THE PLANE TABLE
The setting up the plane table includes the following three operations.
1. Centering the plane table
2. Leveling the plane table
3. Orientation of plane table
CENTERING THE PLANE TABLE:
The table should be set up at a convenient height for working say about 1m. The legs of tripod should be spread well apart and firmly fixed in to the ground. The table should be approximately leveled by tripod legs and judging by the eye. Then the operation of centering is carried out by means of U-frame and plumb bob. The plane table is exactly placed over the ground station by U-frame and plumb bob.
LEVELING THE PLANE TABLE:
The process of leveling is carried out with the help of level tube. The bubble of level tube is brought to center in two directions, which are right angles to each other. This is achieved by moving legs.
ORIENTING THE TABLE:
The process of keeping the plane table always parallel to the position, which is occupied at the first station, is known as orientation. When the plane table is oriented, the lines on the board are parallel to the lines on the ground.