Tracking Footballs With Magnetic Fields

Official NFL footballs are crafted by hand by a company in Chicago called Wilson Sporting Goods. The footballs that are made there typically range from 11 to 11.5 inches in length and weigh anywhere between 14 and 15 ounces on average. Originally, animal bladders lined the outside, occasionally from the inside of a pig, giving the traditional American football the long-standing nickname of a “pigskin.” Now a days, they consist of cowhide leather or vulcanized rubber with laces that are stitched to the top adding mass. This causes the oblong spheres to be naturally lopsided. This is fixed by inserting extra weight to the opposite side of the football balancing it out. Knowing this, a clever hacker will realize that the balancing spot is a perfect place to subtly add a motion tracking transmitter like this one. Doing so makes it possible to the track not only the position of the ball on the field, but its precise location in 3D space!

Since each football is unique, variations between one ball to another exist. This means that embedding a circuit into a football only modifies the equipment slightly, which is a good thing because sports fanatics tend to be very opinionated about whether or not technology should influence the game. So long as the transmitter and loop antenna added to the air bladder doesn’t pass that threshold of about an ounce (or so) difference in weight, then the football itself really isn’t affected much.

The research for this project was developed and tested at the NC State and Carnegie Mellon Universities with the help of funding from Disney (who owns ESPN). Using magnetic fields was chosen instead of other ball tracking systems that are camera-based because it would allow the computer to recognize the football when pile ups occur. Unlike soccer, the footballs in the NFL are usually hidden from view.

The question now is “will the NFL accept this type of system?” They already have integrated instant replay to the game; and as of the 2014 season, teams have Microsoft tablets on the sideline which are used by coaches and referees for in-between play analytics. Yet, the game still uses the same old ‘stick and chain’ method that was initiated in 1907 to measure downs. Implementing it in high schools or colleges would serve as a prototype. From there, the researchers could try to get into pre-season games before attempting nationwide integration. But will fans like it? Will it take away from the game? It’s up to you to decide.

[via Vox]

33 thoughts on “Tracking Footballs With Magnetic Fields

    1. Throwing a football is a sign of weakness. The game is all about ball control. When the ball is in the air it is not under direct control. The very best teams of all time never had to relinquish control by throwing the ball around. They would destroy you on the ground! Time of possession is everything. If the other team has no time with the ball then how can they score? But if you have the ball all of the time you can certainly manage to put some points on the board. 1 point is a win too.

      1. “The very best teams of all time never had to relinquish control by throwing the ball around.”


        “Time of possession is everything. If the other team has no time with the ball then how can they score? ”


        “the whole correlation versus causation thing. Increasing time of possession does not necessarily result in wins, but rather the score of the game may dictate how a team possesses the football.”


        “1 point is a win too.”


        You can keep the ball on the ground for 10 minutes and score 3 points on a field goal.

        You can put the ball in the air for 10 seconds and score 6 points on a touchdown.

        You just demolished your own argument! 10 seconds and 6 points beats 10 minutes and 3 points.

      2. Not sure if serious, but every successful team over the last 40+ years have been good at throwing. Running on every play would be great if you could do it, but once teams start defending against the run by putting their bigger, stronger, but slower players in, you’re not going to get too many first downs on the ground.

        1. I never said playing great football was easy. Bigger, stronger, slower, players also tend to tire out quickly too. You just have to be bigger, stronger, tougher, and quicker than they are. You have to keep on driving up the middle, and sticking it to them, until they can’t take it anymore! Everyone breaks. Run right over them and grind them into the turf. That’s football.

  1. what good is knowing the precise position of the football when the scrambled brains of the players are unable to process this information?

    maybe the inventor should just directly assault the football players and get the trauma over with sooner than later

  2. The real question is the resolution of the system. I can’t see the system being accurate enough using magnetic fields in the volume of space required by a football field to really be an improvement over optical tracking systems… especially not without the sensors interfering with play.

    1. Considering that in World War 2 the USA developed electronic artillery fuses using vacuum tubes. Yeah, shells shot out of cannons. Solid state stuff probably will do just fine in sporting equipment.

  3. “In this work, we present three-dimensional position and orientation measurements using the magneto-quasistatic system and complex image theory over an area of 27.43 m × 27.43 m. Inverting the theoretical expression for the voltage measured at the terminals of the receiving loops to determine three-dimensional position and orientation resulted in mean and median geometric position errors of 0.77 m and 0.71 m, respectively; inclination orientation mean and median errors of 9.67° and 8.24°, respectively; and azimuthal orientation mean and median errors of 2.84° and 2.25°, respectively.”
    Too much error to use with an HMD in place of the ball, for VR head position tracking. Bummer…

  4. I seem to recall stories that some football plays used to involve attempting to deceive people about where the ball is.

    How soon before the players have heads up displays to track the ball, other players, etc. And before somebody employs ball spoofers to manipulate the balls apparent position.
    (Or for that matter manipulate the apparent positions of the players to the RFID tracking system.)

    Reminds me of the Rowland Emmett cartoon featuring Frisbee’s directional wood (a radio controlled lawn bowling ball).

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