One of the most notable sports broadcast innovations is the first-down line overlaid on football broadcasts, originally proposed in 1978 but first used in 1998 (on ESPN with the Sportvision line, and on CBS with the Princeton Video Image line). Since then, that line has become almost omnipresent in football broadcasts. But it wasn’t there for some key plays in the Penn State-Michigan State game on ABC Saturday thanks to the snow, with play-by-play announcer Sean McDonough apologizing for that on the broadcast:
"We apologize for the lack of the yellow first-down line, but the snow makes that technologically impossible at the moment until we can clear off some of those lines. We won't do that, the grounds crew at Spartan Stadium will." pic.twitter.com/Kxktr20xRa
— The Comeback (@thecomeback) November 27, 2021
What does the snow have to do with it? Well, a HowStuffWorks article from Shel Brannan on the Sportvision First & 10 system explains some of the issues involved in projecting that line:
It takes a tractor-trailer rig of equipment, including eight computers and at least four people, to accomplish this task
Here are some of the problems that must be solved in order for this system to work:
The system has to know the orientation of the field with respect to the camera so that it can paint the first-down line with the correct perspective from that camera’s point of view.
The system has to know, in that same perspective framework, exactly where every yard line is.
…Another key piece is a computerized 3-D model of the field. The computers know exactly where the cameras are located in the 3-D model and can orient the virtual first-down line on the field accordingly. The model also accounts for things like the crest of the field and the location of the yard lines on the field.
Color palettes are also critical to the system. The computers must be able to distinguish between grass, on which the line should be painted, and everything else (players, referees, the ball, etc.), on which it should not. Color palettes solve this problem.
So there are at least three things there that could be affected by a snowy field. The most important is the system “knowing exactly where every yard line is,” which isn’t possible when the yard lines are covered in snow. But beyond that, the amount of snow here could also throw off the 3-D model. And the color palettes are another potential problem. At any rate, much of this game has been played without the first-down line, which is a big change from the normal viewing experience.
