Direction Measurement

In measuring the direction of a survey line the following precautions should be taken with compass.

(a) Correctly Centre the compass on the station.

(b) Level the compass and make sure needle is free to move.

(c) Only after vibration of graduation circle/needle is stopped take the reading. Use the knob, if it is necessary.

(d) Tap the top of the glass of compass gently to remove sluggishness of the needle and take the reading after vibration stops.

(e) Whereas taking reading parallax should be ignored.

(f) Care should be taken to keep away iron and steel objects such as, metal framed, key bunch spectacles, chain, iron buttons, arrows etc.

(g) If to clean top of glass of compass handkerchief is used, the glass is charged with electricity.

Local attraction is induced As a result of it. Apply moist fingers to clean the glass to avoid this problem.

(h) Fold the prism and object vane if the compass is not in use on the top of glass plate, so that to avoid unnecessary wear of the pivot needle is lifted from the pivot.

(i) Fore bearings and back bearings should be taken for all survey lines. Bearing should be taken to that station also, if any other survey station is visible which helps in verifying survey work.