You have just taken a satellite fix on your ship and from
there the Master traced a new course line on the chart which is 130° True. The
variation for the locality is 10° West the deviation is 6° East. Find the compass
error and then solve for the compass course to steer.
Given:
130°T =
Course
10° W =
Variation
6° W = Deviation
What is asked?
Compass
error and compass course to steer
Solution:
In problem
like this I’m reminded of the mnemonic that says, “True virgin makes dull companion”. It would be easy if we do the
tabulation.
True
True course = 130°
Virgin Variation = 10° W
Makes Magnetic =
Dull Deviation = 6° E
Companion Compass course =
When converting true course to compass course, west is to be added and east will be minus. So since our
variation is west, we have to add it to True course. And we have to subtract
the magnetic course by the deviation because it is east.
True True course = 130°
Virgin Variation = + 10° W
Makes Magnetic = 140°
Dull Deviation = - 6° E
Companion
Compass course = 134° per standard
compass (psc)
Now let us solve for the compass error.
Compass error = Compass course - True course
= 134° - 130°
= 4° west
= 4° west
- The error is “west” because the compass course is greater than the true course.
Compass best, error
west.
Compass lest, error
east.
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