Plotting pitches

Plotting pitches is another major component of the @UmpScorecards platform that deserves explanation.

If you’ve read the explainer discussing the true strike zone, you may be asking yourself: if the top and bottom of the strike zone move in between pitches, how can you plot each missed call on one strike zone?

There are multiple solutions to this problem. For example, Baseball Savant chooses to plot all pitches at their recorded horizontal and vertical location on a single standardized strike zone, regardless of the top and bottom of the strike zone on any particular pitch. The MLB Gameday app, on the other hand, changes the zone between at-bats, but uses a standardized strike zone for all pitches within an at-bat.

In choosing our approach, we first concluded that the most important aspect of a missed call to represent accurately on our graphics was a pitch’s distance away from the strike zone’s border, as opposed to the pitch’s precise location in 3 dimensional space. With this in mind, here is an example of how our plotting heuristic works in practice: imagine two incorrectly called pitches – one with Aaron Judge batting and the other with Jose Altuve batting – each 2 inches above the strike zone. While these pitches crossed the plate at different heights (Judge’s strike zone ends much higher than Altuve’s), they would both be plotted at the same height on our graphics. In short, we plot pitches relative to their respective strike zones, instead of according to their precise location in space.