[Bongle]

These are all for distance.

Method 1: once you see identify which blob is actually the rectangle, you could do some empirical tests to map blob size in pixels to distance (a team I worked with in 2006 did this and it worked well, thought that was a solid target rather than a rectangle with a hole in the middle)

Method 2: Since the height of the retro-reflective blob won't actually change that much depending on your robot's view of it (until you get very close to the baskets), empirically develop a function mapping blob heights to distance

Method 3: Take method 1 and 2, and average their results.

Method 4: Use knowledge of the properties of the camera lens, and do methods 1 and 2 mathematically instead of empirically. This is harder, but more accurate.

There are lots of other ways, but those are the ones I can think of from the top of my head that I'm pretty sure will work. The hard part for each will be identifying which blob is the backboard, and making sure that a robot or other obstacle in front of you isn't obscuring the blob or cutting it in two.