Whenever a ship is under way it is necessary to compare the ships
compasses to make sure that they are operating properly. This is
accomplished by using the compass calculations and checking the
compasses against the true course.
The following table represents an excerpt from the Magnetic Compass
36 04 W
074 14 W
36 05 W
074 18 W
In this example the date, time, latitude, and longitude of the observation
are noted. The master gyro is reading 120; the error determined by the
morning azimuth is 1.0 E. Remember, if the compass is least the error
is east; you would add the error to obtain the true heading. Knowing
our true heading, we can now apply our variation and compare the
degaussing at 1022
As you can see, this is the practical application of your newly acquired
compass calculation skills. Practice by filling in the blanks for the 1025
entry. When under way, the compasses must be compared every
one-half hour and at each course change.
Note: There is an exception; if a ship is in a formation and changing
course frequently, or the ship is alongside another ship, each course
change does not need to be recorded. Use the following statement in the
Remarks column: "Steering various courses while alongside (in
formation)." A comparison must still be made every one-half hour!