Plotting of Inaccessible Points on a Plane Table by Radiation

Introduction:
A plane table is a surveying instrument that is used for plotting a map of an area or any drawing that requires plotting on a sheet of paper. It is used to plot inaccessible points on a map by radiation method.

Radiation Method:
Radiation method is a method of plotting inaccessible points on a map by extending imaginary lines from the instrument station to the point to be plotted. This method is used when the point cannot be directly observed from the instrument station.

Procedure:
The procedure for plotting inaccessible points on a plane table by radiation is as follows:

Step 1: Set up the plane table at a convenient location such that it has a clear view of the area to be plotted.

Step 2: Orient the table to the North using a compass or by sighting a distant object.

Step 3: Select an instrument station from where the inaccessible point is visible. Mark this station on the map.

Step 4: Sight the inaccessible point using the alidade and measure the angle between the instrument station and the point.

Step 5: Select another instrument station that has a clear view of the inaccessible point. Mark this station on the map.

Step 6: Sight the second instrument station using the alidade and measure the angle between the second station and the inaccessible point.

Step 7: From the first instrument station, draw a line on the map in the direction of the angle measured in step 4.

Step 8: From the second instrument station, draw a line on the map in the direction of the angle measured in step 6.

Step 9: The point where the two lines intersect is the location of the inaccessible point.

Advantages of Radiation Method:
- It is a quick and simple method for plotting inaccessible points.
- It is accurate when the instrument stations are properly selected.

Limitations of Radiation Method:
- It cannot be used when the point is not visible from any of the instrument stations.
- It requires a clear line of sight between the instrument station and the inaccessible point.

It's correct answer is intersection