Civil Engineering - Surveying - Discussion

I think Option E is correct.

Yes, E is correct one.

I also agree with option E.

Graduation is in WCB does not mean that this is more accurate.

Yes, option E is correct.

But surveyor compass more accurate then prismatic compass.

Yes E is correct answer.

Because both these parameters helps in taking errorless readings.

Option E is correct.

I think Option E is correct.

The main difference between the two instruments is that the surveyor's compass is usually the larger and more accurate instrument, and is generally used on a stand or tripod. The prismatic compass, on the other hand, is often a small instrument which is held in the hand for observing and is therefore employed in the rougher classes of work. The graduations on this prismatic compass are situated on a light aluminium ring fastened to the needle, and the zero of the graduations coincides with the south point of the needle. The graduations, therefore, remain stationary with the needle, and the index turns with the sighting vanes. Since the circle is read at the observer's (rather than the target's) end, the graduations run clockwise from the south end of the needle (0° to 360°), whereas, in the surveyor's compass, the graduations run anti-clockwise from the north.

The prismatic attachment consists of a 45° reflecting prism with the eye and reading faces made slightly convex so as to magnify the image of the graduations. This might be helpful for better understanding.