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Friday, May 14, 2021

Developing MLB’s Automated Ball/Strike System (ABS)

The single most important requirement for ABS implementation is the accuracy of the pitch arc being generated. To this end, MLB performs ground-truth testing at every ballpark to evaluate the accuracy and precision of in-stadia tracking systems; the methodology for this was well-covered in an MLB Technology Blog post by Clay Nunnally in December 2019.

Just as important as accuracy for ABS is latency. Currently, there is some intentional delay between when the pitch is received and when the umpire makes their call, which allows the umpire to take a brief moment to make their decision. That brief moment is the window in which ABS must consistently deliver a call to the umpire; anything longer than that and the umpire has to make the call themselves to avoid delaying the game.

The other main constraint is tracking system reliability. In order to effectively standardize the called strike zone, it is not sufficient to quickly and accurately relay a ball/strike call to the umpire some of the time, or most of the time; that goal must be achieved all of the time. It would not matter that 50 percent of pitches are called instantaneously with perfect accuracy if some percentage of pitches are either not tracked at all, significantly delayed in producing a tracking result, or poorly tracked. MLB spends significant effort monitoring the tracking system to ensure it is producing timely and accurate results.

Finally, there are some cases where, even in a game where ABS is operational, the umpire will make the final determination of a ball or a strike being called based on criteria other than the strike zone. ABS is specifically focused on the strike zone and the flight of the ball, so the umpire retains personal responsibility for judging the other criteria that help determine pitch outcomes, such as checked swings or catcher’s interference. Using ABS allows the umpire to be better focused on anything that would result in a decision without consideration for the actual pitch location.


RoyalsRetro (AG#1F) Posted: May 14, 2021 at 11:06 AM | 2 comment(s) Login to Bookmark
  Tags: robot umpires

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   1. sanny manguillen Posted: May 14, 2021 at 03:14 PM (#6018855)
From the article: "...otherwise uses default strike zones based on a player’s height."

I'm guessing this means that every year in spring training there will be a "measurement day," and that the measurements will be preceded by 20-mile hikes carrying 30-pound packs? There will be a great advantage to shaving an inch off the strike zone for literally every pitch through the course of the season. Will a guy even be permitted to get shorter (re-measured) during the season?

It seems inevitable that whatever calculations are chosen for the height of the strike zone will suit the comfort of the bulk of players between about 5'10" and 6'3". I think very tall and short players, and weirdly shaped guys generally, will become rarer under this system.
   2. winnipegwhip Posted: May 14, 2021 at 04:21 PM (#6018864)

Former bell ringer to start for Bombers in season opener.

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