Question 1 of 27070
Q
Your vessel receives a distress call from a vessel reporting her position as LAT 35°01'S, LONG 18°51'W. Your position is LAT 30°18'S, LONG 21°42'W. Determine the true course from your vessel to the vessel in distress by Mercator sailing.
A
160°T
B
153°T
C
135°T
D
149°T
Question 1 / 2707066636eea28f7522a1c51b7ef
Question 1 of 2707066636eea28f7522a1c51b7ef

Your vessel receives a distress call from a vessel reporting her position as LAT 35°01'S, LONG 18°51'W. Your position is LAT 30°18'S, LONG 21°42'W. Determine the true course from your vessel to the vessel in distress by Mercator sailing.

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Question 1 of 27070
Q

Your vessel receives a distress call from a vessel reporting her position as LAT 35°01'S, LONG 18°51'W. Your position is LAT 30°18'S, LONG 21°42'W. Determine the true course from your vessel to the vessel in distress by Mercator sailing.

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🔍 Key Concepts

• Mercator sailing relationships between difference of longitude, meridional parts, and course • Converting latitude and longitude to difference of latitude (D.Lat) and difference of longitude (D.Long) with correct E/W and N/S signs • Using meridional parts tables (or formula) to get difference of meridional parts (D.M.P.) and then finding course from \( \tan C = \frac{D.Long}{D.M.P.} \)

💭 Think About

• First decide: from your position to the distress vessel, are you going generally NE, SE, SW, or NW? Eliminate any course options that don’t fit that general direction. • Work out the numerical values of D.Lat and D.Long between the two positions, being careful with south latitudes and west longitudes. Which one is larger in absolute value, and what does that suggest about whether the course is closer to due north–south or due east–west? • After computing D.M.P. for the two latitudes, form the ratio D.Long / D.M.P. and estimate the angle whose tangent is that ratio. Which of the multiple-choice courses best matches that angle and the correct quadrant (SE, SW, etc.)?

✅ Before You Answer

• Confirm which vessel is farther south and which is farther west before deciding the direction of travel. • Check the signs: D.Lat (N or S?) and D.Long (E or W?) must match the direction from your vessel to the distress vessel. • Make sure you use meridional parts for both latitudes and take their difference, not just the raw difference of latitude, when applying Mercator sailing.