Who Painted That Yellow First Down Line on the Football Field?

Ever wonder about that yellow first down line we see on the football field during broadcasts?

Because we love a good conspiracy, there are plenty of folks who remain convinced the lines are added with powerful lasers or disappearing paint. We’re not sure about that paint theory… do sports ball gnomes run out on the field between plays to repaint the lines?

As it turns out, the reality is not far from the fantasy—it’s a pretty impressive technological undertaking, shared with your local TV meteorologist, to make those lines we take for granted appear under your favorite player’s shoes.

Canuck Roots

After a shot-down proposal in the late 1970s, part of the inspiration came from hockey, when in 1996, FOX introduced a nifty glowing puck graphic overlay on that tiny little hunk of rubber so easily lost amid the chaos of grown men fighting on ice.

Infrared transmitters were embedded inside the puck, which communicated with sensors scattered around the outside of the rink. This allowed the system to follow the puck by creating a blue glow around it. When the puck speed exceeded 70 miles per hour, the effect changed to a red comet streak. Think dramatic shots on goal.

Fan reviews were mixed on “glow puck,” and the effect was retired a few years later. But entrepreneurs are nothing if not persistent, so the engineers at FOX Sports who came up with this stuff left and founded their own company—SportVision, Inc.

Make a new plan, Stan

Future National Inventors Hall of Fame inductee Stan Honey founded SportVision in 1998. Prior to going solo, Honey worked at News Corporation (owner of FOX Sports, among other things), where he helped launch broadcast innovations like the glow puck.

While rookie players were fighting through 1998 pre-season games to earn roster spots, SportVision was testing and furiously fine-tuning a new system they hoped to sell to ESPN for NFL game broadcasts. Parked in a separate truck next to the ESPN command trailer, the team sent a test feed complete with the new first down yellow line.

During the last pre-season game in Kansas City, the system worked pretty well, with only a bit of line jitter. After a couple more weeks in the lab, the system was ready for its public launch during a regular season game between the Baltimore Ravens and the Cincinnati Bengals on September 27, 1998.

A few weeks after that, former collaborator but now rival company Princeton Video Image launched its version of a virtual first down line in a Steelers-Lions game televised by CBS.

The Magic… Exposed

Step one in the process is for the tech gurus to create a digital map of each field prior to the game using sophisticated laser technology. Remember, dudes paint the lines on the field by hand, and who knows if they’re a bit hungover. Also, remember that each field is curved to different degrees depending on the local climate—the center from goal to goal is higher than at the sidelines to allow for drainage.

Once the computer has a virtual map, it can attempt the business of trying to calibrate cameras with constantly moving action on the field. Not only are the players moving, but through pan, tilt and zoom, the camera image is in non-stop motion, too. This is just the beginning of a hairy technological process.

The system not only needs to know the precise location of each camera around the field, but each needs to be equipped with sensors to monitor and transmit pan, tilt and zoom information to the system. And the cameras need to be calibrated with each other to know which is providing the current live feed.

And it gets even harder. Camera lenses introduce a bit of distortion to the picture, so while the white lines actually painted on the field are straight, the image on your TV screen has a bit of curvature. So, the technology has to introduce just the right amount of imperfection to the yellow line, too, or else it would look different than the lines painted on the field.

You won’t be surprised to know a mathematician was part of the original development team.

Uniform conflict resolution

A more subtle feature of “make or break” importance is making sure that the yellow line appears painted on the grass at all times. When a player runs or falls across that line, it must be “drawn,” so it’s underneath them as if it were painted on the blades of grass or astroturf.

That takes some doing and is the part borrowed from your local TV affiliate’s weather team. For each game, the shades of green (and maybe brown, depending on the grass condition) are sampled and programmed into the computers—leveraging the chroma-keying “green screen” process. Then, the players’ uniform colors are sampled and factored in. Once the computer understands the color shades of the field (and remember, it has to account for things like passing clouds and rain or snow), it can work on the gargantuan math problem of figuring out where to add yellow in each frame of live video. Don’t forget that cameras are moving throughout all of this, so the position of each pixel of the first down line must be re-calculated relentlessly. All of this work is done with less than a one-second delay from real-time action.

Big moves

So there you have it. We’d be remiss not to mention Jed Drake, head of Event Production at ESPN at the time. For this to get off the ground, the SportVision team needed a sales commitment. Seeing the potential but not knowing how fans would react to artificial elements being introduced to the raw view of live sports, he took the plunge and signed a one-year exclusive contract on behalf of ESPN. The rest is history.

If you’re watching football this season, thank the engineers at SportVision and Princeton Video Image, but don’t forget to give a nod to your local weatherperson.

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