Temporary Adjustments of Prismatic Compass | Compass Surveying
In this article, we will be discussing step by step method for making Temporary adjustments in Prismatic Compass necessary for carrying out Compass Surveys.
- Fixing the compass to thr tripod
- Centering the compass
- Levelling the compass
- Sighting the object
- Observation of bearings
Fixing the compass to the tripod
The box of prismatic compass is fixed to a spindle of ball and socket joint. By the ball and socket arrangement, this can be quickly levelled and rotated in any direction.
Centering the compass
The prismatic compass is centered over a survey station correctly by means of a plumb bob or by dropping a pebble from the centre of the instrument.
Levelling the compass
The compass is quickly levelled by ball and socket arrangement by eye judgement.
It should be levelled in such a way that dial moves freely and does not touch the rim of the bob.
Sighting the object
The object is sighted with the help of eye vane and object vane in the compass.
The surveyor views through the eye vane and rotate the box until the ranging rod at a station is bisected.
Observation of Bearing
After citing the object correctly, the bearing of the survey lines are noted through prism at which the line of sight and object cuts the image of the graduation on the dial.