METHOD OF USING A COMPASS

METHOD OF USING A COMPASS

To have a reading from a compass, these temporary adjustments are needed:

(i) Centring: The compass needs to be fixed to the stand and set around the station. To centre the compass legs on the tripod stand should be moved inward-outward or in an circumferential direction. To check centring plumb works well or a pebble dropped around the centre of the compass.

(ii) Levelling: In compass survey perfect levelling seriously isn't necessary, but it should be sufficient to allow for free suspension of permanent magnetic filling device. For checking levelling a bubble level is provided in many compasses. After centring bubble should be ensured in the middle of the circle provided for it into the level. If it is not within that circle, circumferential movements can be provided for the legs of tripod to make certain without disturbing centring the levelling is going to be achieved.

(iii) Focussing the prism: In prismatic compass, to focus this specific prism on graduated circle, it is attachment is slided up as well as down till the readings are usually clearly visible. There is not any such requirement in surveyors compass. Another steps are required for observing bearing of your line, say, AB:

(i) Centre the compass around the.

(ii) Level the compass.

(iii) Concentration the prism, if prismatic compass is employed.

(iv) Rotate the box till ranging rod at B is sighted over the line of sight.

(v) Produce the needle to rest making use of knob.

(vi) Take the reading and note it into the field book. Care should be taken to determine that the line of sight seriously isn't disturbed involving the line of sighting the object along with the time of reading the retaining.