Surveying
Local attraction in compass surveying may exist due to

presence of magnetic substances near the instrument
friction of the needle at the pivot
incorrect levelling of the magnetic needle
loss of magnetism of the needle

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Surveying
The rise and fall method

is not suitable for levelling with tilting levels
provides a check on the reduction of intermediate point levels
is less accurate than height of instrument method
quicker and less tedious for large number of intermediate sights

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