KarmaZone

The system

KarmaZone is an optical based electronic strike zone system for baseball. The system uses two high speed cameras to capture the trajectory of the baseball and calculate the location when it passes the visual surface perpendicular to the front edge of the home plate — that is, the strike zone location.

This was a joint project of National Taiwan University of Sport (NTUS) and Feng Chia University (FCU), funded by the Ministry of Science and Technology.

Accuracy against Trackman

We compared our result to the Trackman installed at NTUS, and the one installed at Tianmu Stadium used by a professional team, the Dragons. Taking Trackman as the ground truth, our system’s correlation on plate location is very high.

We also checked the points that are not that close, and found that based on our footage obtained from the high speed cameras, Trackman might not always be correct.

The width of the home plate is 17 inches, and we, like the Trackman, use the center as 0 for the X axis. The direction toward the left handed hitter (first base) is negative, and toward the right handed hitter (third base) is positive.

Review and deployment

KarmaZone saves the footage for every single pitch. The pitcher, hitter, catcher and the umpire can all review the video files after the game to verify their decision.

The system was installed at four stadiums in Taiwan. Three of them are home stadiums to professional teams in the CPBL, the pro baseball league played in Taiwan. The system was stable and reliable, and was used in live TV broadcast.