Let’s Play Ball: Machine Vision Cameras in Professional Baseball
A history of baseball statistics collection
Baseball is a skill based sport that has remained consistent over time, making it easy to compare past and current players. Batting and pitching averages have been documented for years, but statistics concerning field players have been difficult to measure. In the 1800’s baseball was tracked with “box scores”, which tracked offensive moves like the “number of runs scored”; then came the “line score”, which reported runs, hits, and errors. In 1971, the Society for American Baseball research was formed and made up of 16 professional statisticians, which has now grown to 7,000 members. Radar guns and stopwatches were used to determine statistics, for example the speed of a pitch or how fast a player runs to home plate.
FIELDf/x: Digital tracking and analysis
Sportvision, Inc. (Chicago, IL), a leader in sports broadcasting technology used in the NFL, MLB, NASCAR, The Olympic Games, NHL, PGA TOUR, NBA, only to name a few has introduced FIELDf/x, a service, which for the first time in 150 years allows objective field data to be collected and analyzed. FIELDf/x uses Sportvision's baseball software technology to track and digitally record the position of all players, pitches, hit balls and throws in near real-time. The computed information reveals quantitative defensive statistics, including the difficulty of a catch, the probability of a particular fielder making that catch, and a comparison of the True Defensive Range of all the fielders at once.
FIELDf/x uses four Prosilica GX cameras by Allied Vision Technologies (AVT) that are mounted on the stadium structure inside weatherproof enclosures overlooking the field. The cameras image continuously at 30 frames per second and produce a constant stream of video data at 230 MB/s during the game, which amounts to approximately 2.5 terabytes of data to record and process for a typical 3 hour baseball game. Live camera feeds combined with Sportvision’s object-recognition software enables FIELDf/x to supply a digital record of players performance. FIELDf/x measures the defense player’s speed, positioning, accuracy, and reaction time. It also tracks the trajectory of the ball and players are mapped on the field, so you can see exactly what happens during play. The data output is transferred to a database, which can then be accessed by teams’ coaches, scouts and managers to help them prepare game tactics, recruit players or select a bench line-up.
Doug Ferrell, FIELDf/x Technical Lead at Sportvision comments on the decision to select the Prosilica GX cameras for this application: “ A GigE Vision camera was a must for us due to the simple fact that the cameras need to be mounted many hundreds of feet from the computer hardware. Dynamic range is also important as we have to operate in lighting conditions varying from full sun day games to night games in older parks which have less than ideal lighting. Varying conditions are also challenging, for instance where part of the field is in bright sun and part in shade. The packed 12-bit output mode of the GX enables us to handle the more challenging dynamic range situations by trading frame rate for data bandwidth when necessary. In most stadiums at least one of the cameras will need to resolve a 2.9” baseball at a distance of 600’ or more so we have a tough resolution vs. field of view trade-off to make. The wide range of resolutions on offer from AVT helped us optimize it. The Prosilica GX cameras have been robust in the field with few problems and no failures to date. We have also found the AVT PvAPI Software Development Kit easy to use and integrate into our system.”
FIELDf/x has now been implemented in five ballparks across North America