Comment received about earth radius in km as used in great circle calculation.

Earth radius in km

Greetings Eric!

I tried your "Great circle azimuth bearing and range calculator"
and have a suggestion for a better "great circle radius": You
use "111.15/deg" which corresponds to a radius of about 6368.4259

What--if any--equation/theory is it based on?   None - it was just my approximation for earth radius.

A much better "great circle radius" would be the ELLIPSOIDAL
(not just elliptical) quadratic mean radius, which equals
[.25 * (3a^2 + b^2)]^.5, which, for Earth (a = 6378.135, b = 6356.75),
works out to 6372.795477598, or about 111.226264/deg

~Kaimbridge~

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Earth radius in km - Page created 12 Sept 2004