Comparing Ways of Seeing: Virtual Strike Zones

Comparing Ways of Seeing: Virtual Strike Zones


Human vision is one way to measure the path of a ball traveling through the strike zone. Video replay is another way to review an umpire’s calls. Another way to evaluate pitches is through animations that combine video and computer-generated algorithms. This method predicts the path of a baseball traveling through a “virtual” strike zone.

Use the resources on the Comparing and Measuring Moving Objects E-Sheet to answer the questions on this sheet.

Pitch Traxx Demonstration Movies

Look at the Ventura clip
How is the delivery of a pitch modeled through animation?



How is the path of the ball shown?



Where do you think the electronic ump is located? How is the angle of the electronic ump different than the angle of a live umpire?



Is there anything that the electronic ump can’t see from this angle?



Look at the Alfonzo clip
Compare the two pitches shown on the clip. What makes it more difficult to call each of these pitches a strike or a ball?



What variables affect the electronic umpire’s ability to evaluate the pitch’s location?


Look at the Guzman clip
Compare what the live umpire saw and what the electronic umpire saw. The batter backs away. Why?



Why does the umpire make the wrong call? What is the pitch doing that makes it difficult to evaluate the pitch?



Is this animated/simulated version of the path of the ball really accurate? What flaws might be in this system?



One famous scientist who studies the physics of baseball movement says the system is 95% accurate, but that the last 5% is very expensive. This means the system is flawed to some degree.



To what extent is it acceptable to live with a system with these flaws?



Describe these aspects of the pitch shown on the clip:




On the Ball

How Pitch Traxx Works
Read the following description. See if you can identify possible areas of question/concern in terms of the design of the system.

The way Pitch Traxx works is like this: two Sony single-chip CCD cameras are mounted above first base and third base. These cameras zoom in on the ball as it makes its 4/10 of a second journey to the plate. The standard black and white security cameras track the position of the ball in flight from 16 points, so they can trace the trajectory of the ball.

The system uses information from Robert Adair’s book, The Physics of Baseball, to determine the ball’s position and speed in the gaps between the sampled points. The software tracks and stores every pitch for renewal and comparison.

By the time the ball hits the catcher’s mitt, all the numbers are crunched and the information is sent to a data broadcaster for the net and interactive TV, and a standard network graphics workstation with proprietary software in the truck. That way, the absolute location of the ball as it relates to the virtual baseball field can be given.

A video image is used to track pitch speed, break, and location. Cameras at the field level snap a photo of the batter when the ball is approximately halfway to home plate, enabling a Questec operator to establish a vertical strike zone for each pitch.

The system is calibrated to account for different camera locations in each park.

The system merges several technologies: Web, television, camera, and 3-D animation. It incorporates image processing, photogrammetry, physics, and high-speed digital cameras.

Some umpires have said the system doesn’t work perfectly. One umpire said a hitter swung and missed a pitch out of the strike zone; UIS marked it as a ball. Another ump talks about how the hitter crouched to bunt and this fooled the UIS system into calling the pitch a ball.

From this description, what are some possible strengths and weaknesses of the design of this system?



What is the purpose of the electronic umpire system?



What are some of the difficulties of calling strikes consistently?


What kinds of mistakes is the electronic umpire system prone to make?



Live umpires are “second-guessed” by fans and players. The umpire will never change the strike call, however. How does the electronic umpire second guess itself, and thereby give itself a chance to correct a bad call?



What pitch characteristics does the electronic umpire system measure?



What are some of the human considerations that have to come into play when considering an electronic umpire system?



Compare the flaws of a human umpire to an electronic umpire.



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