NBA Leaps Into a New World of STATS
By Carolyn Braff
While the Los Angeles Lakers are working toward winning their 15th national title, the NBA is working the kinks out of a brand-new way to collect the statistics surrounding those titles. STATS Inc., the NBA’s partner for global data distribution, is developing a tracking system that collects real-time positioning data of NBA players, referees, and the ball. During games three, four, and five of the NBA Finals, STATS is collecting the data necessary to transform their successful soccer-specific algorithm into a basketball-friendly application.
From the Pitch to the Parquet
In December 2008, STATS acquired SportVu, an Israeli-based company specializing in motion-capture technology. SportVu is regularly utilized at soccer games, tracking the speed of the players and ball, as well as their locations throughout the match. Adapting the technology for basketball, however, posed some challenges.
“Soccer players don’t bunch together like they do in the NBA,” explains Steve Hellmuth, executive vice president of operations and technology for the NBA. “They also are on a green field, so they’re much more distinct as objects.”
In soccer, the SportVu technology tracks the midsection of a player’s torso, but on a basketball court, that analysis was not as clear.
“In basketball, the game is much faster, and there is a lot more bunching together of players under the basket,” explains Brian Kopp, VP of strategic planning for STATS. “Instead of tracking the torso, we’re tracking the players’ heads because there’s more space by the head. If you’re standing shoulder-to-shoulder, while there may not be space by your torso, by your head there’s almost always going to be space.”
Seeing in Stereo
The tracking software is based on military aerospace technology. Using a predictive model–and without outfitting the players with chips or any other device–the software identifies an object as the ball or a player’s head, and then follows where that object can move. Six CMOS HD 16:9 video cameras capture 30 frames of video per second, along with five data points to accompany that video: an object ID, a time stamp, an X coordinate, a Y coordinate, and a Z coordinate. The coordinates are based on a pre-fabricated court grid that allows the software to place the objects in space.
The cameras are spread in a semicircle around the arena.
“That allows us to have stereovision, a 3D view of the court,” Kopp explains. “Rather than just one angle, as we have in soccer, where we use three cameras, for basketball, we have multiple angles.”
For game four in Orlando, FL, the cameras were rigged near the ceiling of six different luxury boxes, but if the series goes back to Los Angeles for game six, the STATS team will test out new positions as they search for the best possible fit.
Eyes on the Ball
Thus far, the player-tracking algorithms have worked well in their transition from the pitch to the parquet, except for one critical move.
“Where a player is doing a crossover dribble, that really confused the machine,” Hellmuth explains. “They didn’t have an algorithm that said that a player movement could be left-right, left-right before moving to the left or right, so they had to put some fuzzy logic in there to include that a player could move around like that.”
Also, because the player tracking is now based on the head, instead of the torso, STATS had to write a separate ball-tracking engine, so that the system will not mistake a player’s head for the ball.
“We wrote a separate code and have a separate engine because the ball moves so quickly,” Kopp explains. “The system knows that’s not a head because it’s hitting the floor, it’s moving around, it’s going way up on shots. That allows us to be more accurate with ball tracking.”
The system is so accurate, in fact, that STATS was able to confirm a goaltending call in the first quarter of game three.
“We could track the arc of the ball, and the ball was indeed on its way down,” Hellmuth explains. “It had only traveled down six inches before Dwight Howard swatted it away, but because the ball was on its downward path, it was a goaltending charge. You really see how difficult a referee’s job is, and it was fun to see that.”
The Ceiling’s the Limit
Once the data has been collected through the STATS system, the statistical information available to the league multiplies exponentially.
“The data that I capture for a possession from the current stats system that I have might include an assist and a three-point shot,” Hellmuth explains. “With this system, on that same possession, I’m going to know exactly where everybody on the court was, what play was run, what defense the opponent was in, the location of the shot, the trajectory of the shot–I go from having just two bits of information to a huge repository of data that can be analyzed about that possession.”
Player speed, distance, ball speed, and positional data can all be streamed out in real time, based on an operator query or a predetermined formula. That information can be seamlessly integrated into a broadcast, as well.
“Currently, at any given time, a network can flash up a player’s points, rebounds, and assists,” Kopp explains. “We can flash up the distance they’ve run, their speed, the individual time of possession–once you have that data set, it’s up to the imagination what you can calculate.”
One for All
The STATS system requires just 2 HP desktops, 1 HP laptop and 6 HD cameras to operate, so the slim profile required to process this amount of data makes it easy to fit into every arena’s budget. Hellmuth hopes to have one of these systems installed in every NBA arena by the beginning of the 2010 season, once the algorithms have been perfected.
“This will ultimately replace the current system and become the heart of the NBA stats system, but we have a long way to go,” Hellmuth says. “Next year, we’re going to test and refine and develop a five-year plan around this.”