title: Distance between two points in OpenCV
body: <p>I want to measure actual distance between two points like on the road there is a vehicle in front of me,Whats the distance between me and the vehicle?</p>
  
  <p>I proceeded like this :</p>
  
  <p>1) Found the Perspective Transform to get the top view.</p>
  
  <p>2) Then tried to find the distance.</p>
  
  <p>Problem is that I am unable to get the proper top view.</p>
  
  <p>If there is any alternate way please tell.</p>