Other Tech:
http://spectrum.ieee.org/consumer-electronics/audiovideo/all-in-the-game
Present Tech:
http://sportsillustrated.cnn.com/nfl/news/20130718/nfl-birth-of-the-yellow-line/
http://mashable.com/2013/09/25/yellow-first-down-line/
http://entertainment.howstuffworks.com/first-down-line.htm
http://www.todayifoundout.com/index.php/2011/10/how-the-lines-on-a-televised-nfl-game-work/
Future Tech:
http://www.cnbc.com/id/40685217
http://extramustard.si.com/2013/07/18/nfl-fans-can-see-a-virtual-first-down-line-on-tv-will-they-ever-see-one-at-games/
http://www.firstdownlaser.com/index.html
http://www.usatoday.com/story/sports/nfl/2013/12/02/first-down-laser-system-officiating-error-redskins/3809743/
Youtube Link for Future Tech
https://www.youtube.com/watch?v=vlXpQxS5i9g
http://spectrum.ieee.org/consumer-electronics/audiovideo/all-in-the-game
Present Tech:
http://sportsillustrated.cnn.com/nfl/news/20130718/nfl-birth-of-the-yellow-line/
http://mashable.com/2013/09/25/yellow-first-down-line/
http://entertainment.howstuffworks.com/first-down-line.htm
http://www.todayifoundout.com/index.php/2011/10/how-the-lines-on-a-televised-nfl-game-work/
Future Tech:
http://www.cnbc.com/id/40685217
http://extramustard.si.com/2013/07/18/nfl-fans-can-see-a-virtual-first-down-line-on-tv-will-they-ever-see-one-at-games/
http://www.firstdownlaser.com/index.html
http://www.usatoday.com/story/sports/nfl/2013/12/02/first-down-laser-system-officiating-error-redskins/3809743/
Youtube Link for Future Tech
https://www.youtube.com/watch?v=vlXpQxS5i9g