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Camera coordinates to real world plane coordinates

asked 2019-10-23 04:00:05 -0500

Mirano gravatar image

updated 2019-10-23 04:13:07 -0500

Hi everyone!

I searched the Internet to find a solution to my specific problem but couldn't find any usable solutions. The problem is: I'm tracking vehicles in a video, and I need to transform the tracked coordinates in a real world plane coordinate system. I just need the (X,Y) coordinate and no height (Z). Via GPS i was able to get some (X,Y) distances from my camera location (0,0) to points in the image:

Pixel coordinate -> world coordinate (in m)
(691, 1045)->(32,27)

(1114, 652)->(234,57)

(427, 680)->(109,83)

(665, 656)->(157,88)

Now my question is: Is it possible to obtain two equations f(x)->X and g(y)->Y where x,y are pixel coordinates and X,Y are real world plane coordinates? And if yes, how?

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answered 2019-10-23 15:30:00 -0500

eyshi gravatar image

To convert the pixel cordinate to world cordinate (X,Y), you need to have a homography matrix (2d-2d) which can be multiplied with pixel cordinates (in homogenous ) to give world cordinates.

Have a look at the findHomography function in opencv. It helps to find the transformation from one plane to other but only the 2D co ordinates can be found.

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Thank you for your reply! I wonder if this is somehow usable? And any idea how it works?

Mirano gravatar imageMirano ( 2019-10-24 00:44:42 -0500 )edit

I haven't used it, but I believe it is simply based on findHomography function : you can read this : and the link you shared also has an ability to manually click the points and import 3d points to find the homography between two.

eyshi gravatar imageeyshi ( 2019-10-28 12:03:19 -0500 )edit

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Asked: 2019-10-23 04:00:05 -0500

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Last updated: Oct 23 '19