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Comment by morgante | Hacker News Reader

Impressive technology, but perhaps someone with more football knowledge could explain why they don't just paint lines on the field?

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The rules for American football can get pretty complicated, but an abbreviated explanation for the yellow line might go something like this:

The team that has the ball has four tries (i.e. downs) to advance the ball 10 yards. If the team that has possession is abl to advance the ball 10 yards or more within four tries, the marker is reset to the next 10 yards. That's why it's insufficient to mark the lines on the field: if I started at the 10 yard mark and advanced to the 12 yard mark, the line would have to be placed at the 22 yard mark. Painting lines would mean that the entire field would eventually have to be painted and unpainted.

I love American football but it's pretty much an acquired taste (lots of stoppage time, tons of instant replay, incomprehesible rules, heart-breaking inconsistency in the officiating, etc.)

The line moves on every play. Paint would be just a bit cumbersome :)

It represents the "line of scrimmage", which is where the ball starts at the beginning of each play.

The yellow lines marks the line to gain for a first down, not the line of scrimmage. Some broadcasts are showing the line of scrimmage now usually as red or blue IIRC, but yellow is used across the board for the line to gain.

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