Draw a neat lebelled sketch of optical square. Explain its working.
Working of optical square1. Optical square works on principle of optical square to set perpendicular offset
2. Keep ranging rods at point B and C as shown in fig.
3. Observe the both rods through eye vane of optical square ass in figure 6(b) i.e. one direct image and other reflected image.
4. Now, move the along survey line AB with looking through optical square, till both rods coincided as in figure6(c)
5. Once, both rods matched each other point D can be marked on ground and distance CD is measured as perpendicular offset.