Determining the compass deviation by comparing of courses:
The procedures for determining the compass deviation described up to here were based on the comparison of bearings.
But none of these methods cannot be applied to the compasses from which you cannot observe compass bearings.
Therefore, to determine deviation from these compasses, we apply the method called ‘Comparison of Courses‘.
In principle, this method consists to simultaneously read a compass whose compass deviation must found and another whose deviation is known.
Instead of a magnetic compass, the comparison can be made with a gyroscopic compass whose correction is known.
Having the readings in the 8 (eight) cardinal and inter-cardinal courses, deviation is then determined using the following relationships.
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