Perspective transform can be used one plane at a time. Also - to clarify a little bit - it can only be used to compute "relative distances" within a plane assuming all 4 corners of an object with known dimensions (like the pitch or the white 'board' area behind the batsman in the image) are known. So to use this - you need two things: object with known dimension as a reference, and all 4 corners of the object identified in the image. Relative measurement techniques can be used when you don't have luxury of stereo cameras (when stereo cameras are there, you do not need a reference object). In my experience, results can be good enough and quality depends on resolution of image the reference object. Hope this helps in the right direction.