compass

PRISMATIC COMPASS

The graduated ring remains stationary as it is attached to magnetic needle. While the compass needle and the eye sight vane can be rotated
The graduations are made in such a way that 00 or 3600 is at the south, 1800 at north, 900 at south and 2700 at east
Sighting of the object and the taking of reading is done simultaneously
Prismatic compass can be used without a tripod


SURVEYORS COMPASS


The graduated ring being attached to the compass moves with sights. But needle remains stationary when box is rotated
The graduations are made as 00 at north & south 900 at east and west. The east and west positions are interchanged in order to read the bearing in quadrantal bearing system
Sighting the object is done first. Then the reading is to be taken with naked eye by looking above the needle point
Surveyor's compass cannot be used without a tripod