A vessel at LAT 21° 18.5' N, LONG 157° 52.2'...

Question 1 of 2707066636eea28f7522a1c51b7c5

A vessel at LAT 21° 18.5' N, LONG 157° 52.2' W, heads for a destination at LAT 8° 53.0' N, LONG 79° 31.0' W. Determine the true course and distance by Mercator sailing.

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Question 1 of 27070

A vessel at LAT 21° 18.5' N, LONG 157° 52.2' W, heads for a destination at LAT 8° 53.0' N, LONG 79° 31.0' W. Determine the true course and distance by Mercator sailing.

🔍 Key Concepts

• Mercator sailing uses difference of longitude and meridional parts to find course and distance on a Mercator chart • How to compute difference of latitude (D.Lat) and difference of longitude (D.Long), paying attention to E/W signs • Relationship between departure, D.Long, and mean latitude in Mercator sailing

💭 Think About

• First, are the two positions in the same hemisphere for latitude and longitude? How does that affect the signs of D.Lat and D.Long? • Once you have D.Lat and the meridional parts, what trigonometric function relates D.Lat and the difference of meridional parts to the course? • After you find the course, how do you use departure and D.Long to back into the total distance made good?

✅ Before You Answer

• Carefully compute D.Lat and D.Long with correct east/west and north/south signs • Use the meridional parts for the correct latitudes (not just the arithmetic mean latitude) • After you get a course, check if the general direction (east/west and north/south) makes sense between Hawaii area (~157°W) and Panama area (~79°W)