Photo: Robert Houser

Stan Honey, the force behind the creation of Sportvision's yellow football line, poses on a miniature football field in the company's laboratory. The yellow line on the live video feed is generated to appear as if painted on the turf behind Honey.

It is "one of the most significant innovations to football coverage since instant replay," pronounces Fred Gaudelli, executive producer of football for the ABC TV network. And yet it stemmed from a failure in hockey broadcasts that was rejected by die-hard fans as a garish gimmick that defaced their game.

If you've watched a pro football broadcast in the United States lately, you've seen what Gaudelli is talking about: an eerily realistic bright yellow line created on the playing field that shows you exactly how far the offense has to carry the ball to get a first down. "It makes it easier to watch the game, and that is what our job is all about," Gaudelli tells IEEE Spectrum.

That yellow line has become such a staple in U.S. football that no self-respecting network would think of televising a game without it. It even won an Emmy award, for technical innovation. The tiny company that pioneered the technology, Sportvision Inc., with offices in Mountain View, Calif. (headquartered in Chicago), now covers up to 300 games a year with 18 crews. The state-of-the-art workstations the crews use, along with sensors and other hardware and software, solve a barrage of fiendishly difficult image-processing problems in a fraction of a second. And some casual viewers have no idea that the yellow line they see on the field is a computer graphics figment no more "real" than the weather maps that seem to swirl behind television meteorologists.

The story of the yellow-line system, which is called 1st & Ten, is a classically circuitous one that begins in the world of military technology. It goes into the hockey arena, where an early version of Sportvision's tracking technology turned the puck into a flashy orb that streaked across the ice with a fiery tail. It moves onto the football field. And most recently, it has branched out into car racing sponsored by NASCAR (for National Association of Stock Car Automotive Racing, based in Daytona Beach, Fla.), where broadcasters conjure up graphics to give detailed race data in real time. A future version of the technology will even take NASCAR data and channel it to homes, where it will control the movements of virtual cars in interactive video games so couch potatoes can test their racing skills against the pros.

Faster than a speeding puck

Flash back to 1994. IEEE Member Stan Honey is executive vice president of technology for Rupert Murdoch's vast media and entertainment empire, News Corp. (Sydney, Australia). It's June, and Honey is in a meeting with David Hill, then president of News Corp.'s Fox Sports (now chairman and CEO of Fox Sports Television Group). Honey is rhapsodizing about the possibilities of virtual billboards, which would let technicians insert any graphics at will into the images of actual billboards in a stadium. Hill rejects the idea (since implemented by Sportvision and others), but suddenly asks, "Could you track and highlight a hockey puck?"

Honey responds, "I tracked things a lot harder than a hockey puck for the military, David, but you couldn't afford it."

"Just how much would it cost?" Hill asks.

"It would take two years to develop and cost about $2 million," is the reply.

"You don't understand the economics of sports," Hill tells Honey. "Write a memo."

A few days later, back in his office near San Francisco, Honey gets a call from Murdoch, who gets right to the point. "David says you can track and highlight a hockey puck, and you can get it done by the 1996 January All-Star game, and it'd only cost $2 million," Murdoch says. "That is now your highest priority. If anybody asks you about the money, tell them to call me."

With just 18 months to go before the game, Honey immediately starts assembling his team, relying heavily on engineers he'd worked with at SRI International in Menlo Park, Calif., in the early 1980s. The group had developed an over-the-horizon radar, underwater sensors, and an ultraprecise radio-positioning system for the military. Some of them had gone on with Honey when he founded Etak Inc., the company that pioneered in-car vehicle navigation; others had stayed at SRI. With the defense industry slumping, Honey has little trouble arousing interest in his project to break new ground in TV sports broadcasting.

The goal is simple. Make the televised image of a hockey puck glow so it's easier for the viewer to spot, and, when it's going really fast, put a tail on it showing its path. Murdoch and company hope the system can overcome the main complaint about televised hockey: the trouble that casual viewers have in following the fast-moving puck on TV screens.

Honey lays out his proposal. To sum up: it's never been done before, it will undoubtedly be hard, but it's doable. In other words, it's "just the perfect project." He quickly gathers a team of 10 and enlists help from Vista Research LLC (New York City), a group of defense engineers, and Shoreline Studios Inc. (Vancouver, B.C., Canada), a spinoff of Silicon Graphics Inc. (Mountain View, Calif.). The project becomes "a taste of Camelot" for the engineers involved, Honey says.

To track the hockey puck, a number of parameters have to be fed into a computer system and updated continually. First, the system has to know exactly where the broadcast cameras are focused. It also has to have some idea of how each camera lens distorts the image; different brands of lenses vary. It then has to figure out which camera's feed is being displayed to viewers at any moment.

Meanwhile, the system also has to know exactly where the puck is and how fast it is traveling, and then it has to create a graphic based on that data and overlay it onto the video image 60 times a second. All these things have to be exactly synchronized, as the cameras are zooming and panning and the puck is traveling at up to 160 km an hour.

Making it work requires putting infrared transmitters in each hockey puck. Calibrating the system proves difficult. It is finally accomplished by drilling holes in the ice and filling them with blue dye to enable the system to accurately calculate locations on the ice. "It took some convincing to be allowed to do that," recalls Marvin White, now Sportvision's chief technology officer. Technically, the project is a success, and it comes in on budget and on time.

The technology works fine but manages to offend even hockey fans with its lack of subtlety. Fox Sports Television Group (Los Angeles) chooses to highlight the puck with a large, bright, fuzzy blue spot. A red rocket trail appears, painted right over the players, when the puck is traveling at high velocity. "It was comic-strip-like, Flash Gordon," Honey says. Called "FoxTrax," it makes its debut at the 1996 All-Star Game with a series of television commercials and a huge fanfare. Stacks of newspaper articles debate its pros and cons, the "Late Show with David Letterman" spoofs it, and hockey ratings jump to their highest levels ever.

But serious hockey fans hate it. After three years, pro hockey broadcasts in the United States switch networks, and the system dies a quiet death. "There are two ways for a product to fail," Rick Cavallaro, Sportvision's vice president of product development, tells Spectrum. "One is for it not to work; the other is for people to say it works great and we hate it."

In hindsight, Honey says, the system would have been better accepted had it been subtler. Better to have placed the image of a gray disk under the puck—and underneath the players—and shown the puck's track only when it was moving faster than a preset threshold, he says. That track could have been a clean black line, drawn as if by a drafting tool, making it clear that it was to provide information, not entertainment. "It's possible to imagine," Honey says, "that the diehard fans would have seen that as an advantage."