1. Grunt Productions 2007
PRACTICAL APPLICATION OFPRACTICAL APPLICATION OF
COMPASS ERRORSCOMPASS ERRORS
A Brief by Lance Grindley

2. Grunt Productions 2007
COMPASS ROSESCOMPASS ROSES
COMPASS ROSES HAVE TWOCOMPASS ROSES HAVE TWO
CONCENTRIC RINGS WHICH ARE..CONCENTRIC RINGS WHICH ARE..
OUTER RING TRUEOUTER RING TRUE
INNER RING MAGNETICINNER RING MAGNETIC
SMALL SCALE CHARTS ONLY HAVE..SMALL SCALE CHARTS ONLY HAVE..
TRUE COMPASS ROSETRUE COMPASS ROSE

3. Grunt Productions 2007
USING THE COMPASS ROSESUSING THE COMPASS ROSES
BEFORE THE NAVIGATOR USES THEBEFORE THE NAVIGATOR USES THE
MAGNETIC ROSE FOR COMPASSMAGNETIC ROSE FOR COMPASS
COURSE HE MUST..COURSE HE MUST..
APPLY BOTH DEVIATION AND..APPLY BOTH DEVIATION AND..
VARIATION WHICH IS FOUND..VARIATION WHICH IS FOUND..
ON THE N/S LINE OF THE COMPASSON THE N/S LINE OF THE COMPASS
ROSEROSE

4. Grunt Productions 2007
CONVERSION OF MAGNETIC ANDCONVERSION OF MAGNETIC AND
COMPASS COURSES TO TRUECOMPASS COURSES TO TRUE
“The following rule should be applied to
convert Magnetic and Compass bearings to
True”

5. Grunt Productions 2007
EASTERLY VARIATIONEASTERLY VARIATION
Easterly Variation and Deviation are..Easterly Variation and Deviation are..
ADDED or..ADDED or..
Applied CLOCKWISEApplied CLOCKWISE

6. Grunt Productions 2007
WESTERLY VARIATIONWESTERLY VARIATION
Westerly Variation and Deviation are..Westerly Variation and Deviation are..
Subtracted or..Subtracted or..
Applied Anti-ClockwiseApplied Anti-Clockwise

7. Grunt Productions 2007
HOW TO REMEMBER ITHOW TO REMEMBER IT
C AD E T
COMPASS ADD EAST TRUE
REMEMBER! You can manipulate the CADET rule
when calculating from True to Compass by reversing
the rule ie Subtracting East to get Compass from True.

8. Grunt Productions 2007
An ExampleAn Example
A Ship is steering 260C. Variation is 12W in 1982
decreasing 10’ annually. What is the true course the ship is
steering assuming the year is 1985??

9. Grunt Productions 2007
The SolutionThe Solution
 Variation in 1985 is..Variation in 1985 is..
 11.5W..Why..11.5W..Why..
 Because Variation is East and we are adding it to West to reduceBecause Variation is East and we are adding it to West to reduce
the Westerly Variationthe Westerly Variation
 Deviation is given as 1.5E so how do we apply that to the CompassDeviation is given as 1.5E so how do we apply that to the Compass
Heading of 260?..Heading of 260?..
 Correct! We add as it is an Easterly Deviation so the MagneticCorrect! We add as it is an Easterly Deviation so the Magnetic
Heading is…Heading is…
 261.5..Now we must apply the Calculated Variation which is 11.5W261.5..Now we must apply the Calculated Variation which is 11.5W
and the answer is..and the answer is..
 250 True because the Variation is West and it is..250 True because the Variation is West and it is..
 Subtracted or applied Anti-ClockwiseSubtracted or applied Anti-Clockwise

10. Grunt Productions 2007
ANY QUESTIONS?ANY QUESTIONS?
Do I need to learn this?Do I need to learn this?
Why did I join the Company?Why did I join the Company?
Why can I never trap?Why can I never trap?
How many more exams have I got?How many more exams have I got?
Is it too late to transfer to something easierIs it too late to transfer to something easier
like Aviation!?like Aviation!?