Vision - Calculating Distance

[iSpotix]

I have been reading this screensteps article http://wpilib.screenstepslive.com/s/...ng-the-targets under the Distance section and I was confused by some things.

In particular, this:

Vertical target rectangle measures 40 pixels when the camera resolution was 320x240. This means that the blue rectangle width is 2.66*320/30 or 21.28ft.

I understand the 320 but where do the 2.66 and 30 come in? I think I have everything else down.

[rich2202]

In the formula, the 2.66 is Tft, or the size of the target in feet. The length of the target is 32 inches. 32/12= 2 2/3 feet, or 2.66 (or 2.67).

[iSpotix]

Okay, thank you. So then what is the 30 they are dividing by?

Edit: Are they just saying the Tpixel is 30? They go on to divide by 2 and then by tan

[rich2202]

Originally Posted by iSpotix

Okay, thank you. So then what is the 30 they are dividing by?

Edit: Are they just saying the Tpixel is 30? They go on to divide by 2 and then by tan

(2*Tpixel*tanΘ)