How accurate is FoxTrax? Within one-third of a baseball

You can trust FoxTrax, but not all strike zone boxes are created equal

KANSAS CITY, Mo. -- Ever wonder when you're watching Royals telecasts just how accurate the pitch locator FoxTrax is?
Within 1 inch.
That's according to Shaun Carrigan, coordinating producer for Sportvision, the company that tracks the speed and location of every pitch in every major league ballpark.
"The system is accurate now to within 1 inch or one-third of a baseball," Carrigan told, "and I can tell you we're getting more accurate all the time with the technology advances."
That question of accuracy, of course, comes up on any borderline pitch, especially those that go against the Royals.
Take, for example, Kansas City's 3-2 loss to the Tigers last week at Kauffman Stadium. Royals designated hitter Billy Butler was called out on strike three in the bottom of the ninth with a runner on second and none out.
Butler took the borderline 3-2 pitch, thinking it was inside and therefore believing he had drawn a walk to put runners on first and second base. Instead, Tigers closer Jose Valverde got the out, then survived the rest of the inning for a tense, emotional win.
Butler was so enraged with the call that he eventually was ejected.
Butler said afterward that when he viewed television replays in the clubhouse, the pitch was "even further inside than I thought."
FoxTrax did confirm that the pitch was inside by a few inches.

Yet both Carrigan and Fox Sports Kansas City television producer Joe Loverro said missed balls-and-strikes calls are rare.
"What we've seen time after time with FoxTrax is that the umpires are almost always right," Loverro said. "They're very, very good. It is a tough job, and they do it well."
But what also was interesting about the Butler missed call was how various online sites recorded the pitch in regard to their own pitch-locator, strike zone boxes., like FoxTrax, showed the pitch a ball. But some sites, such as, showed the pitch a strike. Somewhat comically, in fact, showed all eight pitches in that Butler at-bat as strikes.
How can that be?
Human error, according to Carrigan.
While Sportvision is set up in every major league ballpark, only rights-holders such as FOX Sports and actually receive the pitch-locator data from Sportvision.
Other sites, Carrigan said, likely have someone sitting in an office somewhere watching the game on TV or online and then interpreting where each pitch ends up in relation to their own site's strike zone box.
"They'll just be guessing," Carrigan said.
FOX Sports and use the same data from Sportvision, so their pitch locations are uniform.  
How the tracking system actually works involves a series of motion equations. The system uses three cameras at each ballpark, including the center-field camera and two others located high above the first base and third base lines.
Each pitch is tracked or shot 60 times per second after it leaves the pitcher's hand toward the plate.
The colored pitch-location dots on the television screen show where the ball crosses the front of the plate, not the back. In theory, some pitches could start out as balls as they reach the front of the plate but wind up nicking the back corner of the plate. Those pitches would be strikes to an umpire but balls outside the FoxTrax box.

"It's very, very rare that a pitch can move around the front of the plate and catch the back like that," Carrigan said. "It happens, but very rare."
The height of the FoxTrax strike zone box varies, of course, from hitter to hitter. That data is loaded by Sportvision for every hitter according to that hitter's strike zone based on the rulebook definition of the zone -- the top of the strike zone is defined as a horizontal line at the midpoint between the top of the batter's shoulders and the top of the uniform pants, and the bottom of the strike zone is a line at the hollow beneath the kneecaps.
One word of caution, though, when viewing games and trying to guess pitch location without the aid of FoxTrax -- the angle of the center field camera is crucial.
"The center field cameras vary from ballpark to ballpark," Carrigan said. "So without the box setup on the screen, pitches can look out of the zone, too high or too low, or inside or outside. But the strike zone box and the tracker are accurate."
At least to within one inch.
You can follow Jeffrey Flanagan on Twitter at @jflanagankc or email him at

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