Coefficient E

Coefficient E This is the part of vessel’s deviation which varies as the cosine of twice the compass course Maximum deviation on N, E, S, W cardinal headings Zero deviation on NE SE SW, NW inter cardinal headings Deviation due to coefficient E given by formula Deviation = E. Cos 2(Comp course) Sign convention +E if east deviation on N & S headings -E if west deviation on N & S headings Quadrennial deviation curve No effect on mean directive force at the compass position

Coefficient E Cause of coefficient E This is due to induction by H component of earth magnetic field on two horizontal soft iron components which are symmetrical about 45° line from stbd/port bow or stbd/port quarter These components are 1) b rod 2) d rod remarks Cause of coefficient A is due to d and b rod unsymmetrical about any line through the compass position

Coefficient E Correction of coefficient E At well sited compass horizontal soft iron are symmetrically distributed about F – A line Both b and d rod cause coefficients A and E Therefore at a well sited compass Coefficient A and E are negligible and hence not corrected If A exist E also exist

Coefficient E