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Given two images of an object taken from the same distance but different vertical angles, is there a way to determine the physical height of the object?

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If you are only interested in the measurement of a single dimension (such as the height or the width or radius) of an object then you do not need multiple images. A single image would have worked if you could determine some scale factors which would depend on the distance of the camera to the object and orientation angles (which would be defined in a scaling matrices) etc.

If the measured dimension was inclined in 3D wrt the camera, then you should also apply projective geometry corrections which would also be defined in respective matrices.

Two images, on the other hand, would let you create the complete 3D environment through which any measurement is easily accomplished by their respective 3D point coordinates inside the world coordinate system. However it's considerably more complex and sensitive to create a precise definition of 3D points from just two images due to several reasons. You need very strict control on the imaging setup.

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  • $\begingroup$ Suppose the distance between the camera and the object is unknown. If two photos of the object are taken some known distance apart, can the height of the object be derived? Is the focal length needed? $\endgroup$ – John M. Oct 20 '17 at 0:17
  • $\begingroup$ Yes stereo vision can (in principle) enable you to detect the object distance, in case it's unknown. $\endgroup$ – Fat32 Oct 20 '17 at 0:19
  • $\begingroup$ But what if the two shots are taken along a straight line to the object? $\endgroup$ – John M. Oct 20 '17 at 0:21
  • $\begingroup$ No then. They must provide enough parallax. $\endgroup$ – Fat32 Oct 20 '17 at 0:23

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