The following questions are based on Chart 13205TR, Block Island Sound, and the supporting publications. On 7 September, you are approaching Block Island Sound from sea. Your vessel has a draft of 20 feet. Equipment on board your vessel includes gyrocompass, magnetic compass, depth finder, and radar. At 1830 your position is LAT 40° 42.5' N, LONG 72° 07.1' W. You are on course 046°T and is making turns for 9 knots. At what time will your vessel be abeam of Buoy "MP"?
• Running fix / DR (dead reckoning) time-distance calculations on a chart • Using speed = distance ÷ time to estimate when you will reach a specific point abeam of your track • Identifying the abeam position relative to a buoy (90° from your heading) on the chart
• First, on Chart 13205TR, plot your 1830 position and your course of 046°T, then draw your DR track toward Block Island Sound. Where along that track will Buoy "MP" lie abeam of you (at right angles to your course)? • Measure the distance along your track from your 1830 position to the point where a line through Buoy "MP" is perpendicular (90°) to your course line. How many nautical miles is that? • Using your 9‑knot speed, convert that distance to time in minutes, then add it to 1830. Which of the choices matches that ETA abeam of "MP"?
• Be sure the line from your track to Buoy "MP" is drawn perpendicular to your course line (046°T) when determining the abeam point. • Use the correct chart scale (nautical miles) when measuring distance along your track, not latitude/longitude spacing in the margin by eye. • Confirm your time calculation: at 9 knots you travel 1.5 NM every 10 minutes. Use that to quickly check if your computed time is reasonable compared to the distances involved.
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