Local attraction in compass surveying may exist due to-
-
A.
Presence of magnetic substances near the
instrument
-
B.
Incorrect levelling of the magnetic needle
-
C.
Friction of the needle at the pivot
-
D.
Loss of magnetism of the needle
Correct Answer:
A. Presence of magnetic substances near the
instrument
Explanation:
The correct answer is the presence of magnetic substances near the instrument. Local attraction occurs when the magnetic needle of a compass is diverted from the magnetic meridian by external magnetic forces. This interference is typically caused by nearby metallic objects such as steel structures, iron pipes, power cables, rails, or even small personal items like keys and belt buckles. While issues like incorrect leveling or friction can cause instrumental errors, they do not constitute local attraction, which specifically refers to external magnetic influence.
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