title: What unit is MongoDB's location indexing in? Meters? Miles?
body: <pre><code>db.posts.ensureIndex({"loc":"2d"})
  </code></pre>
  
  <p>If I do that and query by it...</p>
  
  <p>What are the units?</p>
  
  <pre><code>db.posts.find({"loc": {"$within": {"$center" : [ user_center, user_radius ] }}})
  </code></pre>
  
  <p>What if I want to find something 5 miles away, what would my radius be?</p>