Blown To Bits

The First-Down Line

Friday, January 9th, 2009 by Harry Lewis

Ever wonder how they draw that yellow line on the field in televised football games these days, showing where the first-down marker is? This video explains it nicely. (The part about encoding the camera orientation as an audio signal is just because there is a built-in audio line from the camera to the truck where the processing happens. In other words, it’s adaptive re-use of a technology that is there for another purpose, but isn’t needed — they don’t actually collect the field audio from the cameras.)

You might think the tricky part would be getting the line to go under the players, rather than on top of them, but that’s actually a digital version of an old television technology, the same one that TV meteorologists use. The image they seem to be standing in front of isn’t really there — they are standing in front of a solid blue background. The technology puts the weather map everywhere that’s blue, so it misses the meteorologist (who never wears blue — if one had a blue scarf on, you’d see the weather map right “through” it). In the case of the football field, it’s a uniformly green color, or maybe blue — either way, not a color in the uniforms. If the field gets muddy, this may not work so well, and the yellow line may show gaps.

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