Explain the radiation method of plane table survey with neat sketch.
1 Answer
This method is used when all the points to be plotted are visible from single instrument station. Steps are:
1. Select a suitable point P on the ground such that all the details are visible from it.
2. Center and level the plane table over P.
3. Mark the direction of the North on the sheet by using compass.
4. Locate instrument station( P) on the sheet (p) by using plumbing fork, such that p on sheet is exactly over P on ground.
5. Centering the alidade on point p, sight various details step by step and draw a ray from each detail along the fiducial edge of the alidade.
6. Let the details be named as A, B, C, D, E etc.
7. Now measure the distances of each point from P i.e. PA, PB, PC, PD, PE and plot them to scale on the sheet as pa, pb, pc, pd, pe respectively. Join a, b, c, d, and e to give the outline.