title: Intersection-over-union between two detections
body: <p>I was reading through the paper :
  <a href="http://groups.inf.ed.ac.uk/calvin/Publications/marinIJCV14.pdf">Ferrari et al.</a> in the "Affinity Measures" section. I understood that Ferrari et al. tries to obtain affinity by :</p>
  
  <ol>
  <li>Location affinity - using area of intersection-over-union between two detections</li>
  <li>Appearance affinity - using Euclidean distances between Histograms</li>
  <li>KLT point affinity measure</li>
  </ol>
  
  <p>However, I have 2 main problems:</p>
  
  <ol>
  <li>I cannot understand what is actually meant by intersection-over-union between 2 detections and how to calculate it</li>
  <li>I tried a slightly difference appearance affinity measure. I transformed the RGB detection into HSV..concatenating the Hue and Saturation into 1 vector, and used it to compare with other detections. However, using this technique failed as a detection of a bag had a better similarity score than a detection of the same person's head (with a different orientation).</li>
  </ol>
  
  <p>Any suggestions or solutions to my problems described above? Thank you and your help is very much appreciated.</p>