Template:Great circle distance/er/doc

Usage

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

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

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.