Uploaded April 2014 | Updated September 2026, 1 hour ago

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Sailing School app apps.apple.com/app/sailing-school/id500663978


Use your Deviation Card to convert between Magnetic and Compass Courses.
To create a Deviation Card, steer an accurate course of due North (000 degrees compass).
Take a hand bearing compass to sight along the centerline of the boat and position yourself at the stern, clear of any possible interferences.
Note down the course steered and the reading from the hand bearing compass.
In our case the course steered is 000° and the reading from the hand bearing compass is
002 degrees, alter the course to 030 degrees compass and repeat the procedure.
For the second reading the course steered is 030° and the reading from the hand bearing compass is 033°.
Complete a 360 degree turn, noting your Compass Course and the reading of the hand bearing compass for every 30 degrees alternation.
As you complete the readings, note on the Deviation Card your Compass Courses -
0 degrees, 30 degrees, 60 degrees and so on.
Then on the relevant Compass Course note the respective hand bearing observations.
On the right side, mark the easterly variation and on the left side the westerly.