Rhumb line

Constant-true-course line between two lat/lon points via spherical meridional parts (Bowditch, The American Practical Navigator, sailings).

NAV & TIME

RHUMB LINE18/32SOLVED

From latitude (N+ / S−)

From longitude (E+ / W−)

To latitude (N+ / S−)

To longitude (E+ / W−)

SPHERICAL MODEL

How this is computed

Labeled assumption — Spherical rhumb-line (Bowditch meridional parts) — the constant-course chart-room answer. Great-circle and ellipsoidal (GPS) courses and distances differ, increasingly so on long east–west legs.

Constant-true-course line between two lat/lon points via spherical meridional parts (Bowditch, The American Practical Navigator, sailings). Coordinates are signed decimal degrees, North and East positive. JFK (40.6 N, 73.7 W) to LAX (33.9 N, 118.4 W) is 259° true and about 2,170 nm — matching the ASA CX-3 manual's example. Legs touching a pole fail closed to an em-dash.

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