Template:Great circle distance/er/doc

Usage
Calculates the Earth's radius, in kilometers, at a given latitude. Uses the following formula:

$$R=\sqrt{[(r_1^2*\cos{B})^2+(r_2^2*\sin{B})^2]/[(r_1*\cos{B})^2+(r_2*sin{B})^2]}$$

with latitude $$B$$, radius $$R$$, radius at equator $$r_1=6378.137$$, and radius at pole $$r_2=6356.752$$

With no latitude input, it defaults to the mean Earth radius.