Theory
It is the system of surveying in which field work and plotting work are done simultaneously. It is mainly used for small scale mapping.
Instruments required
1. Plain table
2. Audac trough compass
3. U frame
4. Tape
5. Spirit level
Procedure
Instrument required
1. Alidade
2. Drawing board
3. U frame
4. Trough compass
5. Spirit level
6. Plumb bob
Diagram
1) Alidade : It is made up of a gun metal having length about 50 cm with a straight edge and two vane at the ends as nearly eye vane and object vane.
One of the edge of the diode is leveled and is graduated into centimeter and millimeter. This levelled edges known as fiaducial edge.
2) Drawing board : It is made of a well seasoned wood such as teak or pine and is used for this purpose of plotting. Size of board is 500 X 400 X 15 mm. It is fitted with a leveling head at the bottom. The table is mounted on a tripod by means of a control screw with wing so that the board can be replaced level and clamped in any position.
3) U frame : it is used to being the station point on paper exactly over the center or peg on ground. It resembles the shape of U frame. It is known as U frame.
4) Trough compass : It is used to mark the direction of the magnetic medium on the sheet or plane table. It is also used for orientation purpose.
5) Plumb bob : It is used with U frame to transfer the point on ground to the sheet.
6) Spirit level : To check the level of the table. i.e. used with flat based. It is check testing spirit level in two positions which are at right angles to each other.
Temporary adjustment
In plane surveying the following temporary adjustment were carried out.
1. Centering
2. Leveling
3. Orientation
1) Centering : It was the operation of setting the table over the station on ground so that the point plotted on sheet corresponding to the station accepted the steps taken were,
a. The table was set up approximately leveled at a convenient height.
b. The point on ground was shifted to the drawing sheets using U frame for this the plumb bob was on center or peg.
2) Leveling : It was be operation or setting the force horizontally after the table was centered. The table was approximately leveled by adjusting the legs. The exact leveling on boarding two position of right angles to each other getting bubble central in both direction by moving legs.
3) Orientation : The process by which the position accepted by the board at various survey station were kept parallel. In this method the magnetic north was drawn on paper at a particular station at the next station the through compass was placed along the line of mag north and then the table was turned in such a way that the ends or needle are opposite to errors of the scale. The board was fixed in position by clamps.
Diagram
Method of radiation
In this method the whole traverse was commanded from a single station the procedure was as follows.
1) First shifted a point P so that all the corners of the traverse were seen.
2) First the temporary adjustment were carried out north was marked.
3) The alidade was on point P a line or sight for station was drawn.
4) The distance PA on the ground was measured and put this length to a suitable scale on paper which give point a.
5) Similarly obtained b, c, and d.
6) The points a, b, c, and d are joined to form a traverse.
7) For checking the accuracy or work the distance AB, BC, CD, DA on ground were measured and compaired them with plotted lengths.
