Question

why zero degree is marked at the south end of the graduated circle

Answer 1

In the prismatic compass the circle is read at the observer's end instead of the target's end so the graduations run clockwise from the south end of the needle that is 0 to 360 degrees. While in the surveyor's compass the graduations run anti-clockwise from north.

The prismatic compass is a small instrument which is held in the hand for observing. The graduations are situated on a light aluminium ring fastened to the needle. The 0 degree of the graduations coincides with the south point of the needle. The index turns with the sighting vanes while the graduations remain stationary with the needle.

Answer 2

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