🔍 Key Concepts

• Mercator sailing combines difference of longitude with meridional parts to find course and distance • Compute difference of latitude (D.Lat) and difference of longitude (D.Long) with correct E/W sign • Use table or calculator for meridional parts (M) of the latitudes, then find ΔM and mean latitude

💭 Think About

• First, decide if you are sailing generally SE, SW, NE, or NW from the starting point based on the given latitudes and longitudes. Which direction should the true course roughly fall in? • After finding D.Lat and D.Long, think about whether the course angle should be more influenced by the change in latitude or the change in longitude. • Once you have ΔM and D.Long, how do you set up the right triangle for Mercator sailing to solve for course and then distance?

✅ Before You Answer

• Confirm you computed D.Lat and D.Long with correct signs and units (minutes vs degrees) before using them in any formula • Verify you are using meridional parts for the correct latitudes (not just plain latitudes) and that you took the proper difference (ΔM) • After you get a course, check that its quadrant (NE, SE, SW, NW) matches the relative positions of the two points before comparing to the multiple‑choice answers