You desire to make good a true course of 223°. The variation is 2°E, magnetic compass deviation is 2°E, and gyrocompass error is 1°W. An east-southeast wind produces 3° leeway. What is the course to steer per standard magnetic compass to make the true course good?
• True course vs. course to steer – understand how leeway changes the course you must steer to make good the desired track • Order of applying corrections – remember the standard sequence when going from True to Compass (and include leeway in the right place) • East/West corrections – know when to add or subtract easterly and westerly variation, deviation, and gyro error
• Start from the desired true course made good. Should the leeway (from an ESE wind) make your actual track go left or right of your heading, and therefore should you steer more into or away from the wind? • Work from True down to Standard Magnetic Compass. In what sequence do you apply: leeway, variation, deviation? Do you treat leeway before or after you deal with magnetics? • For each correction (variation 2°E, deviation 2°E, gyro error 1°W), ask: does an easterly correction mean the compass will read higher or lower than true, and does that mean you add or subtract when going from True to Compass?
• Be clear which value you are ultimately solving for: standard magnetic compass course to steer, NOT true or gyro. • Confirm the sign convention you are using: whether you are writing the TVMDC line correctly (e.g., "East is plus" or "East is least") and are consistent from top to bottom. • After you compute the course, compare it with the original true course and the wind direction: does it make sense that you would steer more to one side to compensate for leeway?
No comments yet
Be the first to share your thoughts!