MLB's Zone Evaluation System
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Major League baseball replaced the QuesTec system with Zone Evaluation in all ballparks during the 2009 season, with triple the data collection. The system records the ball's position in flight more than 20 times before it reaches the plate. After each umpire has a plate assignment, the system generates a disk that provides an evaluation of accuracy and illustrates any inconsistencies with the strike zone. Zone Evaluation operated successfully in 99.8 percent of the 2,430 games played during the 2009 season, according to MLB.
But, umpires have pointed out, the accuracy of the system suffers once a pitch enters the strike zone — because the zone hovers above the five-sided plate as more of a three-dimensional prism, not the rectangle that television viewers see. They have maintained that although QuesTec (like Zone Evaluation) collects data in three dimensions, a hitter's position in the batter's box or distractions like bat movement can cloud the information, making it unfit for evaluative decisions about umpires.