Chart Navigation & Plotting · Chart Basics
The principal advantage of the Mercator projection for navigation is that:
- AAreas are shown in their true relative size
- BA rhumb line (constant course) plots as a straight line✓ Correct
- CGreat circles always plot as straight lines
- DThe latitude scale is constant everywhere
Explanation
On a Mercator chart a line of constant course (rhumb line) is a straight line, so a course can be laid down and steered directly. The trade-off is distortion of area and an expanding latitude scale toward the poles; great circles appear curved.
Authority: Bowditch, Pub. No. 9 (Mercator projection)
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