First of all, lets assume you know you current declination value to be -12 degrees (this is the same as 12 degrees Westerly), and you want to be traveling in a true 72 degree path. When you try to determine your current bearing, your compass indicates you are traveling with a bearing of 72 degrees from magnetic north. Knowing your declination value (-12) however, you determine that you are
. actually bearing a course 60 degrees from True North (compass value + declination value = 72 - 12 = 60). At this point, you realize in order to actually travel 72 degrees from True North you will have to add 12 degrees to your planned bearing, and set your compass to 84 degrees. Now traveling at a bearing 84 degrees from magnetic north, you are actually traveling 72 degrees from True North.
