1.how can i obtain real world X and Y from x and y obtained from an image? 2.is scaling factor in x dirn*x=X and scaling factor in y dirn*y=Y ? if then how could i find the scaling factors?
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dx=theRealLengthOfTheView/H; %this you must know, otherwise you can not scale the image.
[y x] = getPosition(h);
Where your X and Y will be the real world distances from the origin (0,0) at the top left corner of the picture.
You need to put a known object (of known length) in the image, such as a yard stick or meter stick or something else that you know the actual real world dimension of.
Neenu, if you already have the stereo image pair and cannot go back and retake the images with an object of known size in the images, then you cannot reliably determine the "real world" scaling factors of the images.
When you are watching Star Wars, and the enormous Imperial Battle Cruiser flies across the screen, how big is that Battle Cruiser in the "real world" ? The real answer is "about half of a metre": they used a detailed model and filmed from very close up to give the impression of a very very big object. You could watch the IMAX 3D version of Star Wars and it would still be the case that the Battle Cruiser was really only about 0.5m long: false perspectives in 3D are still false perspectives.
You could also look at Chapter 11 in Richard Szeliski's book http://szeliski.org/Book/drafts/SzeliskiBook_20100903_draft.pdf