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It is possible to calculate the real-world angle in an image that contains a clear indication of the vanishing points? To illustrate:

Explanatory image

I know it's possible if we know the real-world dimensions of a feature in the same plane to calculate the homography (perspective correction) and use that to correct the measured angle. My question if whether it's possible to do so without knowing those dimensions.

We can make some assumptions which might help, like:

  • the lines on the side of the house are parallel
  • the angle to the top of the roof is 90deg
Robert Massa
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  • Use knowledge about parallel lines , and make perspective correction similar to this http://www.addictivetips.com/windows-tips/easily-correct-image-perspective-vertical-line-distortion/ – minorlogic Feb 03 '16 at 11:27
  • Thanks, it's not clear from the article, but you still need to specify real-world size information. I've downloaded the tool to check. – Robert Massa Feb 03 '16 at 11:53
  • If you know the angle to the top of the roof is 90°, then you know the angle you want to calculate is 45° (assuming the roof is symmetrical) – ctst Feb 03 '16 at 12:19
  • see [calculate 3d coordinate from shadow](http://stackoverflow.com/questions/21643692/calculating-rectangle-3d-coordinate-with-coordinate-its-shadow) to rotate angle then your angle – Ivan.s Feb 04 '16 at 21:17

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