From your 1845 position, you desire to leave Stratford Shoal Middle Ground Light 1.0 mile off your starboard beam at 1900. Which course and speed would you order if you allow for a 2.0 knot current with a set of 180°T?
• Current as a vector with set (direction) and drift (speed in knots) • Difference between course through the water (what you steer) and course over ground (resulting track) • Relative position off the beam at a given time and distance
• On the chart, how would you plot the desired track so that the light is 1.0 mile off your starboard beam at 1900? Think about where your ship must be at 1900 relative to the light. • Once you know the required course over ground, how do you use the current vector (2.0 knots, set 180°T) and time run to find the course to steer and speed through the water? • Which answers have a course that reasonably compensates for a north–south current with set 180°T, and a speed that gives the right distance run in the available time?
• Be sure you are plotting the future ship’s position at 1900 (1.0 NM off the starboard beam), not your 1845 position, when relating it to the light. • Verify you are adding the current vector to the ship’s through‑the‑water vector to obtain the track over ground, not the other way around. • Check that the time from 1845 to 1900 (in hours) multiplied by the candidate speed gives a reasonable distance run consistent with your plotted track length.
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