Seeing Eye to Eye with the Umpire

What You Need


  • Home plate
  • Baseball
  • Glove
  • Helmet
  • Chest protector
  • Video camera
Seeing Eye to Eye with the Umpire


To develop an understanding of how a technology system that measures balls and strikes compares with the human vision system attempting the same task.


This lesson is part of a group of lessons that focus on the social, behavioral, and economic sciences. These lessons are developed by AAAS and funded by the National Science Foundation Grant No. SES-0549096. For more lessons and activities that take a closer look at the social, behavioral, and economic sciences, be sure to check out the SBE Project page.

For the most part, umpires do a great job of accurately evaluating balls and strikes. They use their eyes to measure the location of a very fast object (a pitch) which is often moving at a trajectory that is designed to fool the hitter, often crossing a variable "strike zone."

Nevertheless, the system umpires use to call balls and strikes—human vision—is imperfect. Although instant replay is available on video, at present, major league umpires use only their eyes to call balls and strikes. However, another system, called the Electronic Umpire System, is being used in many major league parks as a way to evaluate umpires. Although this system is not used to second guess an umpire's calls during the game, a CD-ROM is sent to each umpire after the game to "grade" their accuracy. The electronic umpire system uses video cameras and 3-D renderings of the strike zone to determine the path of each pitch through a "virtual" strike zone. Although Major League Baseball continues to use the electronic umpire system, some umpires claim that the good old-fashioned way of using human vision is less prone to errors.

The end result of a flawed system is usually a flawed product. In this activity, students have an opportunity to compare the human system of calling balls and strikes with the electronic umpire system. One of the challenges of teaching this activity is to help students understand that the human eye is indeed a measurement tool—one that measures distance and location. In this regard, it is like a level, or a ruler, or any other tool that must be accurate in order to be useful.

In this activity, students will compare the eyes as a measurement tool of pitches to video and 3-D animations doing the same task. Students will compare optical parts of the eye with camera parts that perform similar functions. They also will take their own turn as umpires and compare their results with other students. Students will investigate how variables affect the "system of umpiring," such as the variable location of the strike zone, the speed and trajectory of pitches, and the angle at which one views the pitch crossing the strike zone.

Students will consider issues related to the human and mechanical models and the materials used to make them. According to the research , "Middle-school students have little understanding about the design process. They do not appear to understand what evaluation of design is or why it is important." (Benchmarks for Science Literacy, p. 349.)

Many students will enjoy the focus on video, 3-D animation, and "hands-on" umpiring. Yet students should realize that old systems often work very well—and in some cases, even better than new systems.

One design consideration that students should be aware of is constraints. As they compare human vision and high-tech, 3-D renderings of fast-moving objects, both systems have limitations. Constraints are inherent in the design of complex systems. By middle school, students already should know that there is no perfect design.

For better or worse, umpires do not invite second-guessing. As a rule, baseball umpires never change a ball or a strike call. Is this a good thing or a bad thing? The lack of a "control mechanism" is one of the factors that makes baseball interesting. According to Benchmarks, "The concept of trade-offs in technology—and more broadly in all social systems—is so important that teachers should put it into as many problem-solving contexts as possible. Students should be explicit in their own proposals about what is being traded off for what." (Benchmarks for Science Literacy, p. 48.)

Finally, feedback is another key element in the development of technological systems. As students compare and contrast their ball and strike calls, they will understand that multiple viewpoints will often provide conflicting data on balls and strikes. Whether or not students agree with every call that another student makes, they will see that conclusive proof as to the accuracy of a call can be elusive, and that a perfect "system" is a rare thing indeed.

In this activity, exact knowledge of the physics of a baseball's trajectory is not required. Students are not expected to understand the complex equations and algorithms needed to calculate the exact path of a ball traveling at high speed through the strike zone. Nevertheless, a basic understanding of gravity and human optics is helpful.

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To help get students motivated and engaged in this lesson, show them the Calling Strikes as a Baseball Umpire. This clip provides information about how to call balls and strikes as an umpire.

Once you have watched this video clip as a class, talk with students about what they expect from an umpire: perfection, consistency, or both? Would baseball be a better game if every umpire's call were perfect? Is the goal of the game really perfection?

Before students engage in the main activity for this lesson, ask them:

  • How accurate can an umpire be? Is perfection possible?
  • Is it possible for a technology system such as instant replay to call balls and strikes perfectly, or does this system have flaws too? Are video replays always accurate?
  • How does the human eye track a pitch's movement in the strike zone?
  • What is the difference between seeing a ball "live" versus seeing a ball cross the plate on television? How does this compare to an "animated" ball crossing the plate on television?

At this point, you are just looking for students' opinions and observations. Explain to them that they will learn about some of these issues during this lesson.


In this part of the lesson, students will engage in an investigation where they compare ways of seeing. To begin, distribute the Comparing Ways of Seeing: Human Vision student sheet. Students should use the Comparing and Measuring Moving Objects student esheet to help them research how vision works. You can find answers to the questions on the student sheet on the Comparing Ways of Seeing teacher sheet.

When students have completed the student sheet, have them present their findings to the class. After the presentations, ask students these questions:

  • In what way is umpiring a measurement "system"? What tools do umpires use to measure pitches?
  • What inputs and outputs are part of human vision?
  • What are some of the constraints of human vision?
  • What does the umpire measure when he or she calls a ball or a strike?
  • In what way is the human eye like a camera?
  • What are some other devices that are used to measure the location of balls and strikes?
  • In what other industries besides baseball is telemetry useful?
  • Why are cause and effect important design considerations for an umpiring system?

Now distribute the Comparing Ways of Seeing: Virtual Strike Zones student sheet and have students use the resources on the esheet to complete this student sheet. You should discuss the questions on the student sheet as a class. You can follow up this discussion with questions like these:

  • Why do you think some umpires question the accuracy of the electronic umpire system? What measurement flaws does the system have?
  • Where is the "blind spot" for the electronic umpire system?
  • Compare human and electronic umpires—which system is more accurate?
  • How does human error affect both systems?

After students have reviewed the 3-D animation and video clips, have them analyze the design considerations that go into the development of 3-D animation and video. Have students form three groups to compare the merits and disadvantages of human vision, video replays, and "virtual" systems such as the one shown at the Pitch Traxx and On the Ball sites.

Ask students questions such as:

  • What is the end purpose of a measurement system for a game?
  • Is the end result of an umpiring system to call a "perfect game" or to simply be consistent in the way balls or strikes are called?

Note: Keep in mind that baseball has long resisted improvements in bats, gloves, and balls for the simple reason that too many changes may actually wreck the game. The end goal is not to create a ball that travels out of the park every time it is hit, nor to create a ball that can be thrown so fast that is impossible to hit.

  • Are new measurement systems always superior to old systems? In what way can a slick look and feel hide design flaws? For example, although the electronic umpiring system seems to provide instant analysis of the path of the ball through the strike zone, in fact it does not track the ball for the last few feet through the strike zone—cameras are blocked from doing this. In this regard, the last few feet of the pitch must be "projected." Also, the strike zone must be adjusted from one batter to the next. How does the new system handle these requirements?

Now students will engage in a hands-on activity where they get to play the role of an umpire and see if they can make accurate calls of pitches traveling in or out of the strike zone. Before doing the activity, students should review the strike zone that Major League Baseball recommends be used to call balls and strikes. This will make their data more valid and allow for useful ball and strike call comparisons with other students. Students should use the You Be the Umpire student sheet to help them do this activity.

After the activity, bring students back together for a class discussion. Ask students to consider this statement from the benchmarks: "Automation, including the use of robots, has changed the nature of work in most fields, including manufacturing. As a result, high-skill, high-knowledge jobs in engineering, computer programming, quality control, supervision, and maintenance are replacing many routine, manual-labor jobs." Ask students to consider whether human umpires will eventually be replaced or forced to use some version of instant replay or the electronic umpiring system. Why or why not?

After they have conducted their investigations, ask students:

  • What did you think about how each participant in the activity called balls and strikes? Are you willing to consider the possibility that one or more of their calls were inaccurate? How can you "prove" a strike call was right or wrong?
  • How do variables such as the ball's speed, location, and movement increase the difficulty of calling pitches accurately?


In general, assess students' understanding based on how well they understand the anatomy and functions of the eye. Students should have a basic understanding of the inputs, outputs, and constraints of human vision versus a mechanical vision system such as the electronic umpire system.

Asking students to discuss the variables that can affect an umpire's calls, such as a pitch's speed, location, and trajectory, should be in the range of students' comprehension. Students should not be expected to explain the physics behind the movement of a pitch. Nor should students be expected to explain the detailed mechanics behind 3-D animations or video image engineering.


The following Internet resources can be used to further explore the topics related to vision, cameras, and animated modeling tools.

How Camcorders Work provides a good introduction to the core components of a camcorder. These elements are discussed: the basics, CCD, lens, formats, and other information. The site contains many images of the internal components of a video camera and simple diagrams showing the basics of image capture and color processing.

Fastball Reaction Time provides an interactive opportunity for students to try to "hit" a baseball traveling in the 4/5 of a second real time that a pitch would actually travel in the major leagues.

Funder Info
National Science Foundation
Science NetLinks is proud to have the National Science Foundation as a funder of this project.

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Lesson Details

Grades Themes Type Project 2061 Benchmarks National Science Standards State Standards