Determine distance to vehicle in image

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I have 2 image:

1) Initial image when I detected car.

2) IPM image when I transformed image to another plan.

I don't have any information about camera parameters. I know the location of the car in original image and in IPM image and I wish to know how can I determinate the distance between the car and the camera. Can we assume the height of the camera is 1 m.

Exist any formula or algorithm for that?