Hence we have these rules, which put in your Note-Book: To convert a compass course into a true course When the Variation is westerly, the true course will be as many points to the left of the compass course as there are points or degrees of Variation.
"Lectures in Navigation"
Ernest Gallaudet Draper
To convert a true course into a compass course The converse of the above rule is true.
"Lectures in Navigation"
Ernest Gallaudet Draper
In order to convert this true course into your compass course, allow for Variation and Deviation according to the rules already given you.
"Lectures in Navigation"
Ernest Gallaudet Draper