To find a magnetic compass course from a true course you must apply

• A. Deviation and variation
• B. Latitude and longitude
• C. Wind and current
• D. Time and distance

Answer: (A)

Converting a true course to what a magnetic compass will show requires correcting for two magnetic influences: variation and deviation. Variation is the difference between true north and magnetic north at your location, shown on charts. Deviation is the local magnetic effect caused by the ship’s own iron, equipment, and other influenced components. By applying variation, you shift from true north toward magnetic north, and by applying deviation, you translate that magnetic direction into the reading your compass would display. The other factors—latitude/longitude, wind and current, or time and distance—don’t alter the compass correction needed for this conversion. Hence, the best answer is that you must apply both deviation and variation.