How to calculate target distance?

[FuzzyLogic]

Another way to calculate distance is to look at the height of the object within a the camera's field of view. Very close to the tower the vision target is at the top of the image, and as you back up it lowers to the middle of the image.

You can either use an empirical function to determine distance (beware, it's not linear though) or use geometry. Our team uses geometry and it's been pretty successful. We typically calculate within 1-3 inches of the actual distance.

This method is also easy to calibrate. Although the pixels-to-distance function isn't linear, the error in the calculation is. Finding the slope of the line allows you to adjust the angle constant in the formula.