Chart Navigation & Plotting · Sailings — Distance from dLat
On a nearly north-south course of 010°T you make a difference of latitude of 60' N. Approximately what distance have you run?
- AAbout 60 NM exactly
- BAbout 61 NM✓ Correct
- CAbout 10 NM
- DAbout 600 NM
Explanation
Distance = dLat ÷ cos(course) = 60' ÷ cos 10° = 60 ÷ 0.985 ≈ 61 NM. Because the course is slightly off due north, the distance run is a little greater than the 60 NM of latitude change. (dLat in minutes ≈ NM along a meridian.)
Authority: Bowditch (Pub. No. 9), Plane Sailing
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