New tech to detect a football's exact position on the field

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

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. Video of the technology in action can be seen here.

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. In other words, the football that has the built-in transmitter could be used in a National Football League game. Antennas, placed around the football field, receive signals from the transmitter and track its location.

But the researchers also had to address another complicating factor.

When low frequency magnetic fields come into contact with the earth - such as the playing surface - the ground essentially absorbs the magnetic field and re-emits it. This secondary field interacts with the original field and confuses the antennas, which can throw off the tracking system's accuracy.

"We realized that we could use a technique developed in the 1960s called complex image theory," Dr. Darmindra Arumugam, lead author of the paper and a former Ph.D. student at Carnegie Mellon now at NASA's Jet Propulsion Laboratory said. "Complex image theory allows us to account for the secondary fields generated by the earth and compensate for them in our model."

The study has been published in IEEE Antennas and Propagation Magazine.