Backboard Pixel Distance Question

[Chris Hibner]

Originally Posted by Glen

The 2012 Vision whitepaper explains on page 9 how to compute the distance from the target. We understand everything but the 56 pixel wide target rectangle (This is the actual quote):



My question is this, where did they get the target rectangle width in pixels (56 in their case)? After all, that isn't a fixed number, it will change accordingly based on how far/close the robot is to the target.

Some clarification would be great.

The pixel width will vary with how far you are away from the target. What you know is how wide the target is (i.e. 2 ft). Using the math in the paper, you can convert the pixel with into how far away you are from the target.

Think about it from your standpoint as a human: the farther you are from something, the smaller it looks, right? With the camera and the math in the paper, you can translate the "how small it looks" directly into "how far away" it is.

The "56" number in the paper is just an example. They said "let's say the camera shows the width of the rectangle is 56 pixles, then that means ..."