distance in the real world

asked 2014-08-27 10:28:24 -0600

shutingjia
11 ●1 ●1

I have done the camera calibration by using 20 check board image, and get the intrinsic parameters and also the extrinsic parameter matrix, say 20 rotation matrix and 20 translation matrix for each check board. My question is if I put a new object in the real world, and know two points's coordinates of the new object in the image, is there any chance to know the distance of the two points on the object in the real world? and how to do that? Cheers!

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answered 2014-08-27 10:41:51 -0600

FooBar
2938 ●9 ●37 http://magazino.eu/

Short: No.

Long: No, you have no chance since you lose the scale of the object when projecting it into the camera. In the projection formulas, you always have expressions as x_px = fX/Z, y_px = fY/Z, so you can't distinguish the points (X,Y,Z) and s*(X,Z,Y) since s is cancelled out during projection. If you see an image of a tree, you don't know if you are far away from a large tree or close to a small toy tree.