Television viewers had been at a disadvantage in knowing where the first-down line is in reference to where the offense is. A small arrow located below the end pole isn't usually visible on the television screen.
But if you've watched any football games in the last few years, you probably noticed the fluorescent yellow or orange line extending from one side of the field to the other -- seemingly painted on the field. In fact, the line is computer generated, representing exactly the spot that the offense must get to for a first down.
Sportvision, a company based in New York City, debuted its "1st and Ten" system on September 27, 1998, and football fans everywhere rejoiced! Sportvision provides ESPN and Fox Sports with the ability to enhance their football telecasts with this technology (you can view images from actual games that used the first-down line on their Web site).
I could not fully understand how the 1st and Ten system works but it basically is a computer-generated video effect and takes a tractor-trailer rig of equipment, including eight computers and at least four people, to accomplish this task.
Source: houstuffworks
