How to find the distance to pixel ratio in a image.

Question

I am trying to find a estimated distance in a image based on the camera height and angle. I know how to find the center of the image distance based off of this equation that I am using

Camera Height $= H$

Camera Angle $= A$

Distance $= D$

$D = \frac{H}{\cos(A)}$

Now how do I find the rest of the distances in the image. I tried using the ratio between the distance and the pixel value, but that does not give me good results.I was going to try to change the angle of the camera but I dont know if that would give me the right results as the camera angle has not really changed would this work?

Any suggestions would be appreciated.

Distance CM PixelValue Ratio 100 449 0.22 200 296 0.68 300 231 1.3 400 194 2.06 500 170 2.94 576 106 5.43

So this is where I am going with this for now as I know all the distances for each angle, but still don't know how to find the slope or change a ratio for distance. I just don't see a patter here.

Answer 1

Firstly you will need to do your analysis in 2 angular dimensions. You will need to know a fair bit. There is no pixel to distance ratio. It is nonlinear. The pixel to azimuth is what you are after. It is still nonlinear, but manufacturers will strive for linearity in this.