DIFFERENCE B/W SURVEYING AND PRISMATIC COMPASS
|Prismatic Compass||Surveying Compass|
|1. Here the reflecting prism carries a sighing slit; therefore, sighting and reading are done simultaneously.
2. Here, the needle and the graduated ring are attached together and remain in constant position when the box is rotated.
3. In the prismatic compass, the graduations are numbered clockwise from zero at the south end of the needle; so that 90O are marked at the west; 180O are marked at the north; and 270O at the east.
4. The figures are written inverted.
5. The prismatic compass may be held in the hand, usu placed on a tripod stand.
|1. Here, the observer has to sight the object first and go around reading the graduation pointed by the north end of the needle.
2. Here, the graduation card is fixed to the box and moves with the sights when the box is turned. The needle remains stationary pointing to the magnetic north.
3. Here, the card is divided into 4 quadrants. The graduations are numbered from 0O to 90O in each quadrate. The zero points are marked with N and S and 90O points with E and W.
The graduations are also measured counterclockwise.
4. The figures are written ordinarily.
5. The Surveyor’s compass must be supported on a sing pointed rod 1.8 m long called a Jacob Staff, or on a light tripod.
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