Touchdown or first down? 3D device to help soccer referees

While referees draw the flak in the ongoing football World Cup in Brazil for controversial decisions, referees in the US can heave a sigh of relief.

They may soon have a new way of determining whether a football team has scored a touchdown or got a first down.

Researchers have developed a system that can track a football in three-dimensional space using low-frequency magnetic fields.

"Low frequency magnetic fields do not interact very strongly with the human body so they are not affected by the players on the field or the stadium environment," said David Ricketts, an associate professor at North Carolina State University in the US.

The researchers designed and built a low-frequency transmitter that is integrated into a football, and is within the standard deviation of accepted professional football weights.

Antennas, placed around the football field, receive signals from the transmitter and track its location.

The technology could be particularly useful for situations when the ball is blocked from view such as goal-line rushing attempts when the ball carrier is often buried at the bottom of a pile of players.

"The technology could also be useful for tracking the forward progress of the ball or for helping viewers follow the ball during games with low visibility - such as games played during heavy snow," Ricketts said.

The study appeared in the journal IEEE Antennas and Propagation Magazine.