RoboUmp Hits the Big Leagues

In Major League Baseball, there are four umpires on the field: one behind each base, and one behind home plate. The home plate ump has arguably the most important job, calling balls and strikes. A strike is basically any hittable pitch, something over the plate, between the batter’s chest and his knees. And a ball is everything else. Accurate calls are critical. But one study from 2018 found that umpires blow about 14 calls every game. That’s 34,000 bad calls every year. And it makes a difference.

A blown strike call can decide a win or a loss, a championship or long and sad off-season. This year, Major League Baseball has introduced a new system to help improve the accuracy of ball-and-strike calls – now, players are allowed to appeal to a so-called “robot umpire” if they disagree with the original, human call on the field.

The “robots” are actually a camera system called ABS, or “Automated Ball-Strike.” The system is similar to missile-guidance technology, and can pinpoint a ball’s location with startling accuracy. Back in 2023, 99% Invisible first covered this story, when the ABS system was introduced in baseball’s minor leagues. Now, with its arrival in the MLB, we revisit that story, and offer an update from producer Chris Berube on how the ABS system has been working out so far.