At 0900, the current is flooding in a direction of 350°T at 1.2 knots. If your engines are turning RPMs for 9 knots, which course should you steer per standard magnetic compass to make good a course of 297° true?
• Set and drift of current and how they affect course made good • Vector triangle (or current triangle) using true course, speed through the water, and current • Converting from true course to per standard compass (psc) using variation and deviation
• First, draw or imagine the current vector from 0900 conditions: where is 350°T relative to north, and how will that push your vessel if you want to make good 297°T? • Construct the current triangle: which side is your ship’s speed (9 knots), which side is the current (1.2 knots), and which side is the desired course made good (297°T)? • After you find the required true heading, think through the sequence of corrections (True–Magnetic–Compass) to convert it to a per standard compass course.
• Be sure you are using speed through the water (9 knots), not speed over ground, in your vector triangle. • Confirm the direction of current (350°T) is the direction toward which the water is moving, and apply it correctly in your diagram. • Verify the final step: when going from true to psc, you apply variation and deviation in the correct direction (remember: "True Virgins Make Dull Companions" or your preferred memory aid).
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