title: Finding real world distance using an image
body: <p>I am working on a project where I need to figure out real world distance of an object with reference to a fixed point using an image.</p>
  
  <p>I have detected the object in a 2D image, using <code>SURF</code>. My object is inside a box now. What will give me the position of the centroid of the object. How can I use this to find out the real word distance?</p>
  
  <p>If I plan to incorporate stereo vision, triangulating the centroid of the object, what is the difference between the distance I obtain here and in the previous method?</p>