How the NFL tracks everything on the field but the ball
From Chinese women’s soccer to the American big leagues, real-time motion tracking is coming to sports43
Most people know radio-frequency identification (RFID) chips as the security tags adorning clothes in stores, but this year they can also be found inside the uniforms of NFL players. As the Atlanta Falcons and Detroit Lions descended upon London this weekend, accompanying them were executives from Zebra Technologies, the company behind the RFID-based motion tracking system that the league is implementing this season. Zebra is in town to try and convince the operators of Wembley Stadium and the rest of the sports world to follow the example set by the NFL. I spoke with them about what makes their technology compelling and the future applications it can have for coaches, fans, and players of all sports.
Using a pair of location beacons embedded in each player’s shoulder pads, the Zebra system is able to measure speed, acceleration, and distance covered in nearly real-time — there’s just a half-second latency — and to within a margin of error of less than 6 inches. Referees and the first-down measuring sticks along the sideline are also equipped with the coin-sized RFID tags, leaving only the ball as an untracked entity on the field. (Zebra is working on a custom transmitter with wider weight distribution for 2015 that will make it possible to track the most critical object without affecting its flight or feel.) The company describes 2014 as a "best effort" year, with half the NFL stadiums being outfitted with its sensor networks and only occasional uses of the technology manifesting themselves in game broadcasts till now. But the vision for this technology is much grander than its present state.
The 2011 CBA already has provisions for location tracking on the field
The obvious first use for precise positional information of this sort is for coaches looking to analyze their players’ performance. Did the wide receiver run the exact route he was supposed to? Did the cornerback keep a disciplined distance away? WIth built-in accelerometers and the redundancy of having two sensors per player, the tracking system knows which way a player is facing and how smoothly he is moving around the field (on top of how quickly). For the players, that will mean an extra layer of accountability, going beyond the already extensive set of statistics that are tracked on each play. There’ll be no dissension from among their ranks, however, since they agreed to wear sensors for tracking of location and health metrics in their 2011 Collective Bargaining Agreement.
The NFL has been preparing to deploy what it calls Next Gen Stats for a long time. It signed up Zebra as its provider this summer after a year-long evaluation period that included other competing solutions. The league’s focus is actually less on providing analytics for its member teams and more on augmenting the fan experience. In fact, in order to ensure fairness, the NFL isn’t releasing the data it’s gathering to the teams until all 31 stadiums have installed the sensor system necessary to track the RFID tags.
Enhancing the fan experience is taking primacy over coach analytics
Thursday Night Football broadcasts on CBS have been the primary beneficiaries of the early use of Next Gen Stats, showing things like JJ Watt’s incredible 20mph speed on a fumble return and the separation that a wide receiver achieves on a successful touchdown pass. Instead of the usual hastily scribbled doodles from the color commentator, viewers are now getting precise lines showing exactly how a player manages to get wide open and an accurate account of each juke, hurdle, or sprint. In a league obsessed with keeping track of all possible player measurables, it’s surprising to find that most physical indicators are measured outside of game conditions, at events like the Scouting Combine each spring. Zebra combines such known metrics as a player’s 40-yard dash time with the data it collects from the game to validate its findings.
What’s unique about this system, versus competing GPS-based alternatives, is the simplicity and ease of implementation. There’s nothing particularly smart about each RFID tag, as it just beams out a message saying "I’m here" 25 times per second that a network of 20 sensors around the bowl of a stadium triangulates to a precise location. Tags only have to be installed once per player per season and can last for years at a time. Their accelerometer data is only transferred when a certain threshold is crossed and high-fidelity location tracking is only enabled during live plays, making the whole thing rather efficient on bandwidth as well. Not that interference should be an issue, since the Zebra tags work in the 6.4GHz ultra wideband range where conventional wireless devices don't.
Now: every move you make. Next: every breath you take
There’s plenty of room for the information gathering to grow. Experiments are already underway to use the Bluetooth Low Energy radio built into the Zebra tags to expand their functionality. One of the future goals will be to figure out a suitable way to attach them to the player’s skin so as to get heart rate and training intensity data as well. Before its NFL deal, Zebra successfully rolled out its system with the Shanghai Women’s Soccer team in China, so it already has a good idea of how to adapt the technology to other sports.
Like RFID tags themselves, Zebra Technologies is a company with a ubiquitous presence that’s rarely felt. It does asset tracking and management for a number of auto companies and counts Walmart as one of its biggest clients. Zebra has a long history of tracking "expensive, mobile, and mission-critical assets," and makes the point that that’s exactly what NFL players are. Now it’s just a matter of getting one of these beacons on the most mobile and mission-critical asset in the game: the ball itself.