Glad You Asked: That yellow line on the field during televised football.(Knight Ridder Newspapers)

Byline: Jeff Elder

Q: How do they make those electronic first-down lines on TV during NFL games? _ John Adams, Indian Trail, N.C.

A: They do it with technology that hustles more than a crazed Ray Lewis in the fourth quarter.

The yellow stripe is created by a video system called 1st & 10. It examines every frame from every camera 30 TIMES A SECOND.

1st & 10 gathers precise information about each camera's view, tilt and angle, and monitors which camera is on the air. It then uses a 3-D model of the field to map the line.

Another part of 1st & 10 breaks the colors of the video broadcast into two palettes: One for the players, and one for the field. The colors for the players (their uniforms, shoes, skin) is never drawn over by the yellow line. …