The First-Down line in football broadcasts...

How exactly do they superimpose the yellow line over the field during broadcasts? A few specific questions:

(1) Is there some sort of “beacon” attached to the first down marker on the side line which is then extrapolated to a line across the field?

(2) Can they do this from all camera angles, or does it require a specially equipped camera (or one that doesn’t change field angle)?

(3) How come the line is underneath the players when they pass over it, but remains on the green grass and white chalk (but doesn’t appear on the white pants of the players?) I presume this is analagous to “green-screen” technology, but I don’t quite get why it works when the players share some of the same colors as the field.

Thanks!

-ollie-

A great explanation can be found
here

For some more information, you can also check out the company’s website at htpp://www.lovetheline.com

I advise people to stay away from howstuffworks.com until they figure out that popup windows are unnecessary. It’s almost as bad as a porn site (from what I hear about porn sites, that is)

Actually, the company’s web site is http://www.sportvision.com

Just get Pop-Up Stopper and HowStuffWorks.com (and others like it) is fine.

Nope - Popup stopper and their ilk are great as far as they go, but companies need to understand that popups are not welcome. Neither are cookies. Most companies have figured out that cookies are unwelcome, but haven’t figured that out about popups yet.

Just like telemarketers - if no one buys this crap, they will get rid of it.

In the interest of not hijacking this thread, Gazoo, please join me in the pit.

http://boards.straightdope.com/sdmb/showthread.php?threadid=101247

To stop popups, you don’t need another program, just turn off javascript in your browser.

Yeah, but turning Javascript off disables other, useful features too. Besides, Pop-up Stopper is freeware.