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How Does the Magic Yellow First-Down Line Work?

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If you attend a Super Bowl party on Sunday, you’ll probably hear at least one casual football viewer ask, “How do they get that yellow first-down line on the field?” While “magic” is a fine answer in its own right, the real explanation is a bit more technologically intense. Let’s have a look at the background and mechanics behind every football fan’s shining beacon, the yellow first-down line.

Like the first-down line, football fans? You owe a tip of your cap to an unlikely source: hockey. According to Allen St. John’s 2009 book The Billion Dollar Game, the first-down line actually emerged from the ashes of one of sports broadcasting’s bigger debacles: the FoxTrax system for hockey, which was designed by a company called Sportvision. FoxTrax – which hockey fans no doubt remember as the much-maligned “technopuck” that debuted in 1996 – employed a system of cameras and sensors around a hockey rink to place a little blue halo around the puck.

FoxTrax wasn't a great fit for NHL broadcasts. Hockey purists hated the intrusion into their game, and casual fans didn’t flock to hockey just because the puck was suddenly easier to follow. However, the system inspired producers to think of new ways to insert computerized images into live sports broadcasts. The idea of using a line to mark the first down in football was a natural extension, and Sportvision debuted its 1st and Ten system during ESPN’s broadcast of a Bengals-Ravens tilt on September 27, 1998. A couple of months later, rival company Princeton Video Image unveiled its Yellow Down Line system during a Steelers-Lions broadcast on CBS. (Sportvision is still kicking, and ESPN acquired all of PVI’s intellectual property in December 2010.)

But How Does It Work?

It takes lots of computers, sensors, and smart technicians. Long before the game starts, technicians make a digital 3-D model of the field, including all of the yard lines. While a football field may look flat to the naked eye, it’s actually subtly curved with a crown in the middle to help rainwater flow away. Each field has its own unique contours, so before the season begins, broadcasters need to get a 3-D model of each stadium’s field.

These models of the field help sidestep the rest of the technological challenges inherent to putting a line on the field. On game day, each camera used in the broadcast contains sensors that record its location, tilt, pan, and zoom and transmit this data to the network’s graphics truck in the stadium’s parking lot. These readings allow the computers in the truck to process exactly where each camera is within the 3-D model and the perspective of each camera. (According to How Stuff Works, the computers recalculate the perspective 30 times per second as the camera moves.)

After they get their hands on all of this information, the folks in the graphics truck know where to put the first-down line, but that’s only part of the task. When you watch games you’ll notice that the first-down line appears to actually be painted on the field; if a player or official crosses the line, he doesn’t turn yellow. Instead, it looks like the player’s cleat is positioned on top of an actual painted line. This effect is fairly straightforward, but it’s difficult to achieve.

To integrate the line onto the field of play, the technicians and their computers put together two separate color palettes before each game. One palette contains the colors – usually greens and browns – that naturally occur on the field’s turf. These colors will automatically be converted into yellow when the line is drawn onto the field. All of the other colors that could show up on the field – things like the players and officials’ uniforms, shoes, and flesh, the ball itself, challenge and penalty flags – go into a separate palette. Colors that appear on this second palette are never converted into yellow when the first-down line is drawn. Thus, if a player’s foot is situated “on” the line, everything around his cleat will turn yellow, but the cleat itself will remain black. According to How Stuff Works, this drawing/colorizing process refreshes sixty times per second.

All this technology—and the people needed to run it—wasn’t cheap at first. It could cost broadcasters anywhere from $25,000 to $30,000 per game to put the yellow line on the field. Sportvision had to deploy a truck and a four-man crew with five racks of equipment. The cost has come down since then, and the process is now less labor intensive. One technician using one or two computers can run the system, according to Sportvision, and some games can even be done without anyone actually at the venue.

Now you can explain it to everyone at your Super Bowl party during one of the less-exciting $4 million commercials.

This post originally appeared in 2011.

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11 Classic Facts About Converse Chucks
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Converse’s Chuck Taylor sneakers have been around since the early 20th century, but they haven’t changed much—until recently. In 2015, The Chuck II—a new line of Converse that looks much the same as the original shoe but with a little more padding and arch support—hit stores. In honor of the kicks' staying power, here are 11 facts about Converse Chuck Taylor All-Stars.  

1. They were originally athletic shoes. 

The Converse All-Star debuted in 1917 as an athletic sneaker. It quickly became the number one shoe for basketball, then a relatively new sport (basketball was invented by James Naismith in 1891, but the NBA wasn't founded until 1946). By the late 1940s, most of the NBA sported Chucks. They remain the best-selling basketball shoes of all time, even though very few people wear them for basketball anymore. (Many teams switched to leather Adidas in the late ‘60s.)

2. Converse previously made rain boots.

The company started in 1908 as a rubber shoe company that produced galoshes.  

3. The All-Star design hasn’t really changed since 1917.

The updated Chuck II is Converse’s first real attempt to update its flagship product since the early 20th century. The company is understandably reticent to shake things up: All-Stars make up the majority of the company’s revenue, and like any classic design, its fans can be die-hards. In the 1990s, when the company tried to introduce All-Stars that were more comfortable and had slightly fewer design inconsistencies, hardcore aficionados rebelled. “They missed the imperfections in the rubber tape that lines the base of the shoe,” according to the Washington Post. The company went back to making a slightly imperfect shoe.

4. Chuck Taylor was a basketball player and trainer ...

Chuck Taylor in 1921. Image Credit: North Carolina State University via Wikimedia Commons // Public Domain

Taylor was a Converse salesman and former professional basketball player who traveled around the country teaching basketball clinics (and selling shoes) starting in the 1920s. His name was added onto an ankle patch on the sneaker in 1932

5. ... And though he sold a lot of Chucks, he wasn't always a great coach.

Taylor is in large part responsible for the shoe’s popularity with athletes (the company rewarded him with an unlimited expense account), but his training advice wasn’t always the best. As former University of North Carolina player Larry Brown told Spin in an oral history of the shoe:

My greatest memory of Chuck Taylor—probably ’61 or ’62—is that he told Coach [Dean] Smith that he’d make us special weighted shoes in Carolina blue. The idea was that we’d wear the weighted shoes in practice, and then during the games, we’d run faster and jump higher. Well, we tried them for one practice and everyone pulled a hamstring.

6. Converse didn’t intend for their shoes to be punk.

“We always thought of ourselves as an athletic shoe company,” John O’Neil, who oversaw Converse’s marketing from 1983 to 1997, told Spin. “We wanted to sell a wholesome shoe.” The company was still touting its shoes as basketball sneakers as late as 2012, and some of its non-Chucks sneakers still have pro endorsers.

7. The company owns a recording studio.

Finally embracing its role in the music scene, the company launched Rubber Tracks, a Brooklyn-based recording studio where bands can record for free, in 2011.

8. Not all the Ramones were fans. 

Chuck Taylors are associated with punk rockers, especially the Ramones, but not everyone in the band wore them. “Dee Dee and I switched over to the Chuck Taylors because they stopped making [the style of] U.S. Keds and Pro-Keds [that we liked],” Marky Ramone told Spin. “Joey never wore them. He needed a lot of arch support and Chuck Taylors are bad for that.”

9. Chucks were initially only high tops. 

In 1962, Converse rolled out its first oxford Chuck Taylor All-Stars. Previously, it had just been a high-top shoe. Four years later, the company would introduce the first colors other than black and white.

10. Rocky ran in them.

In 1976, All-Stars were still considered a viable athletic shoe. If you look closely at the training montage from Rocky, you’ll see the boxer is wearing Chucks. 

11. Wiz Khalifa loves them. 

The rapper named his record label Taylor Ganag Records, in part due to his appreciation for Chuck Taylors. In 2013, he launched a shoe collection with Converse featuring 12 styles. 

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