If you grew up in a house with a football-loving father like I did, you probably had your young little mind blown every NFL Sunday by the yellow line darting under the players' feet. My dad's answer? "Hollywood Magic." Up until the moment I stumbled across this video that was the only answer I had ever gotten.
Later, as I became more acquainted with the video production process through my professional career I started to loosely grasp the fact that it used some green screen techniques, but the intricacies were still lost on me. This video dives in to explain how the cameras work together with 3D renders taken before each game, along with surveying lasers, to put that little line on the field.
Sportvision debuted the "1st and Ten" technology in 1998 on ESPN, and later went on to win an Emmy for "Outstanding Technical Achievement in Sports." Being a total geek when it comes to this stuff I did a bit of digging on Sportvision and came to learn they've won quite a few awards, and they didn't stop after "1st and Ten." I highly recommend checking out their website to see how they're pushing the audience experience forward through their use of broadcast technology.
And for all you motion graphics folks out there, the animation is really well done.