# Template:Great circle distance/er

6371.0008824956

Template documentation

## Usage

{{Great circle distance/er|latitude}}

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

${\displaystyle R={\sqrt {[(r_{1}^{2}*\cos {B})^{2}+(r_{2}^{2}*\sin {B})^{2}]/[(r_{1}*\cos {B})^{2}+(r_{2}*sin{B})^{2}]}}}$

with latitude ${\displaystyle B}$, radius ${\displaystyle R}$, radius at equator ${\displaystyle r_{1}=6378.137}$, and radius at pole ${\displaystyle r_{2}=6356.752}$

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