I was watching the NFL football today and wondering how they visually put down the line of scrimage and the first down marker. Obviously they are superimposed but superimposed very well. As the camera pans they go with it. The shadows fall on it. The grass or astroturf is hidden and everything else is above it.
Tell me about it. I notice it does take them some time to get it done because its not there on the hurry-up-offense. It seems they can do it in about 20 seconds.
Thanks
Chris

I asked a guy who claimed he ran a camera for the NFL about this once. He gave me some song about GPS tracking that just didn't make sense. So, I looked it up. Check this (http://entertainment.howstuffworks.com/question225.htm) out.

That link was pretty informative. I confirmed alot of what I supposed went on and learned alot of what I hadn't counted on.
I don't think I will personally being trying to incorporate that stuff anytime soon into my filming. haha I was hoping there was a simple ingenious program to do it but I didn't really expect it.
Thanks again for the response.
Chris

Yeah, this takes quite a bit of processing power to handle in realtime HD, but if you're not doing this in realtime, there is software (and specialists) that handles virtually everything listed. It can be done with just about any PC or Mac built in the last five years or so.

The discipline is called Matchmoving; basically, matching a CGI camera (in 3d space, orientation and lens length) to a live action clip so additional effects
There are a number of companies that provide software to handle the matchmove. RealViz Matchmover Pro, 2d3 Boujou and SynthEyes to name a few. There's also a free program called Icarus floating around the net for non commercial use.

The thing is, you'll still need a 3D compositing (AE, Shake, Nuke, etc) or CGI app (Maya, 3dMax, XSI, C4D, Lightwave ....... ) to add the graphics.

Something like a first down line in post is fairly easy to do once you have the tools and know how to use them ... admittedly, though .... the learning curve is very challenging, especially if you've never worked with 3D before.