At 0745, you change course to head for The Race. You will leave Race Rock Light bearing due North (000°T) at 0.5nm. If the current has changed to 115°T at 3.5 knots and your speed through the water is 15 knots, what course (pgc) should you steer?
• Current set and drift and how they affect your course made good • Using a current triangle (vector triangle) to combine ship’s motion through the water and current • Difference between true course, compass course (pgc), and course over ground
• Sketch a current triangle: one vector for your speed through the water and one for the current; what must the resultant point toward in order to pass 0.5 nm west of Race Rock Light on a north bearing? • Is the current setting you toward The Race or setting you away from it? Should you steer more into or away from the current to make good the desired track? • Once you find the true course to steer from your plot, how do you convert that to pgc, considering variation and deviation (assume typical exam values from the chart)?
• Be sure the resultant (course over ground) vector actually passes 0.5 nm from Race Rock Light on the correct side at 000°T bearing • Check that the current vector (115°T at 3.5 kn) is drawn from the correct point and to scale relative to your 15‑knot speed vector • Verify that your final pgc value is adjusted properly from true course using the variation and deviation given on the exam chart legend
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