how do they put the down-markers (football game) on tv?

Question

the markers on the field and make it look like it is part of the football field ( you can see the players step on top of it ) ?

Answer 1

It's a similar device that allows them to write on the screen to show the movement of players and the ball. It just marks a certain yard line and then follows the pixels around the screen however the camera turns.

Answer 2

it is just on the tv i guess they use a comp. to do it so people at home can see the first down

Answer 3

its hi-tech paint they put on the grass that glows when ever the ball is snapped. new technology