Story provided by Vox –

Sports broadcasts are wallpapered with gratuitous graphics. They’re moving, they’re shiny, they sound like Transformers. Take them or leave them, the experience of watching football doesn’t really change.

(NBC)

With one exception: The yellow first-down line. Since the late 1990s, the virtual yellow line has been quietly enhancing football broadcasts by giving viewers a live, intuitive guide to the state of play. The graphic is engineered to appear painted on the field, rather than simply plopped on top of the players, so it doesn’t distract from the game at all.

(ESPN)

The line debuted during a September 27, 1998, game between the Baltimore Ravens and the Cincinnati Bengals. It was developed by a company called Sportvision Inc. and operated by six people in a 48-foot semi-truck parked outside the stadium. J.R. Gloudemans, one of Sportvision’s founding engineers, recalled the early days of the yellow line in an interview with the Engineering and Technology History Wiki:

We got lucky the first season because we only did night games (ESPN Sunday Night Football) so the lighting was consistent. Snow and rain caused problems and on one occasion, there was torrential downpour at a Kansas City game.… Another tough stadium was Candlestick in San Francisco. The Niners wear that sort of brownish pants. Back then when baseball was also played on that field, the dirt from the infield was a close color match to the uniforms. So keying in those circumstances was very tricky.

(To understand how dirt and weather affect the yellow line, check out the video above.)

ESPN was the only network that immediately agreed to pay the steep price of $25,000 per game. Before long, other companies began offering the yellow line to the other networks, and now you won’t see a football game without it.

In fact, when Fox Sports tried to save money by cutting the line from its broadcasts 15 years ago, there was an outcry from fans. Sportvision set up a website for comments (available now thanks to the WaybackMachine):

10/22/01 10:34:53 AM — Bonnie: Lose the fancy broadcast desks, the fake field floor, the flying statistic graphics and the sound effects and bring back the line! … $1,000,000 / a year? Come on – what’s that? One more Superbowl ad? I’d be willing to watch another one and make the game another minute longer to save the line.

About a month later, Fox brought back the line, having found a sponsor (Intel) to cover the cost.

So how does the line actually work? Watch the short video above to find out.