If you attend a Super Bowl party on Sunday, youБll probably hear at least one casual football viewer ask, БHow do they get that yellow first-down line on the field? Б While БmagicБ is a fine answer in its own right, the real explanation is a bit more technologically intense. LetБs have a look at the background and mechanics behind every football fanБs shining beacon: the yellow first-down line. According to Allen St. JohnБs 2009 book
The Billion Dollar Game: Behind the Scenes of the Greatest Day in American Sport – Super Bowl Sunday, the first-down line actually emerged from the ashes of one of sports broadcastingБs bigger debacles: the FoxTrax system for hockey, which was designed by a company called Sportvision. Бwhich hockey fans no doubt remember as the much-maligned БtechnopuckБ that debuted in 1996Бemployed 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 didnБt 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 during ESPNБs 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 PVIБs intellectual property in December 2010. ) BUT HOW DOES IT WORK? It takes lots of computers, sensors, and smart technicians to make this little yellow line happen.
Long before the game begins, technicians make a digital 3D model of the field, including all of the yard lines. While a football field may look flat to the naked eye, itБs 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 3D model of each stadiumБs 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 networkБs graphics truck in the stadiumБs parking lot. These readings allow the computers in the truck to process exactly where each camera is within the 3D model and the perspective of each camera. (According to, 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 thatБs only part of the task. When you watch a football game on television, youБll notice that the first-down line appears to actually be painted on the field; if a player or official crosses the line, he doesnБt turn yellow.
Instead, it looks like the playerБs cleat is positioned on top of an actual painted line. This effect is fairly straightforward, but itБs 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 colorsБusually greens and brownsБthat naturally occur on the fieldБs turf. These colors will automatically be converted into yellow when the line is drawn on to the field. All of the other colors that could show up on the fieldБthings like uniforms, shoes, footballs, and penalty flagsБgo 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 playerБs foot is situated БonБ 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 60 times per second. All this technologyБand the people needed to run itБwasnБt 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. Have you got a Big Question you\’d like us to answer? If so, let us know by emailing us at. This post originally appeared in 2011. People Think Coffins Are Buried Six Feet Under, But The Truth Is Quite Different Mobsters in movies love to say that they\’re going to put people \”six feet under\” to imply that their associates are about to be nice and dead. but is there a reason why the bodies are supposed to be six feet below the surface? The people at now have an answer to this morbid question. In the process of figuring it out, they discovered that these regulations aren\’t as standard as we tend to think. Although the phrase \”six feet under\” is thrown around a lot, the truth about burial restrictions is that they vary by region. In fact, some areas allow graves to be as shallow as two feet from the surface. whereas other communities encourage graves to be a whopping 12 feet deep (to allow room for the burial of relatives). For the most part, being buried \”six feet under\” is a commonly used phrase and nothing more. Many think that the phrase may have originated during the Great Plague of 1665 in London. The thought is that bodies were ordered to be buried at least six feet underground to prevent the spread of the disease. However, it\’s been proven that the plague couldn\’t spread from corpses to the living, so this theory has been thrown out.