E. Level tube:- Level tube is used for setting the table in a level position.
F. The plumbing fork or U frame:- It is used for centering purposes.
G. Other drawing materials:- paper, drawing pins, clips, clamps, pins, pencils, rubber, Scale, etc.
Setting up the plane table:- The level of the tripod is spread apart and kept at working height. The legs are fixed into the ground.
The table should be so placed over the station on the ground that the point plotted On the sheet corresponding to the station occupied should be exactly over the Station on the ground. This made use of a U frame. To do this place the pointed end Of the upper leg of the form coinciding with the point on the paper and suspended a Plumb line from the other leg. Shift the table bodily until the plumb bob hangs over The center of the station peg. The Table is then leveled by use leveling tube. The level table keeps on parallel and Perpendicular direction, and level by the movement of legs.
Orienting the table. The preparation of keeping the table at each of the successive stations parallel
To the position which it occupied at the first station is known as orientation. It carries on Two ways.
Orientation by the magnetic needle. Keep the compass on the table and turned the table until
The magnet read zero. Then clamped the table.
Orientation by back sight:-In this method the table is oriented by use of the line of sight parallel to a line drawn on the paper. Let us a line be drawn on the paper. Set the table at station B on the ground, make the center, and level of the respect of b point on the paper. Turn the table until the line of sight of BA is parallel to ba on the paper.