Chart Navigation & Plotting · Mercator Sailing — Meridional Parts
Meridional parts are used in Mercator sailing to:
- AAccount for the latitude expansion of the Mercator chart when computing course and difference of longitude✓ Correct
- BMeasure distance in degrees
- CCorrect for compass deviation
- DFind the time of tide
Explanation
A Mercator chart stretches latitude toward the poles. Meridional parts express each latitude's expanded distance from the equator, allowing the rhumb-line course to be found from tan(course) = dLong ÷ (difference of meridional parts).
Authority: Bowditch (Pub. No. 9), Mercator sailing
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