So, I grabbed some images from robocup 2014 that we took of the goal with the netting.  One has no people behind it and the other had people behind it.  I ran both Canny and Hough on it to see if the netting would stand out.

Canny with people behind the net:

Canny with no people behind:

 

Then just to show that this pattern just doesn’t show up everywhere I took a random sample of the image with some people:

 

And one without people which included the net:

 

So, it doesn’t look like the net will make the difference.  So, what kind of algorithm will be able to see something even I can’t see?