title: calculate the area of a polygon in ruby
body: <p>I have an array of latitude/longitude coordinate pairs that represent a polygon. I'm trying to determine the total area within that polygon. How would I go about doing that in Ruby? </p>
  
  <p>Here's an example array of the polygon:</p>
  
  <pre><code>[[37.7663613767094, -122.452969210084], [37.7674219449606, -122.444718340349], [37.7701838510542, -122.445330289514], [37.7709974013834, -122.439159589248], [37.7700761930893, -122.438861402472], [37.7703501163684, -122.436868738421], [37.7712650571321, -122.437078116573], [37.7736056746515, -122.437533130227], [37.7714671036087, -122.453964210266], [37.7663613767094, -122.452969210084]]
  </code></pre>