The Physics of Baseball
The Physics of BaseballBy the end of the 2007 season, all MLB ballparks will be equipped with video cameras that track each pitched ball and determine its trajectory precisely. These data are used on ESPN broadcasts under the name K-Zone. They are also used by Fox and the Regional Sports Networks to show pitch locations, pitch sequences, and other such things that the announcers deem useful to the viewer. Also MLB Gameday, the on-line pitch-by-pitch account of each game, uses the tracking information to report the pitch speed (both at release and as it crosses the plate) and the amount and angle of the "break". This technology is known as the PITCHf/x system. The pitch logs from Gameday are available to anyone who wishes to access them. These data provide a wealth of information about the trajectory of pitched baseballs which can be used for both the scientific study of the aerodynamics of a baseball in flight and for studies of direct importance to the game itself. To read and listen to MLB's own description of the PITCHf/x system, click here. To learn more about this system, some of the analysis that people have done with the pitch logs, and how you can download files so that you can do your own analysis, continue reading and click on the appropriate links.
Sportvision: This is the company responsible for the pitch-tracking technology, including the software used to reconstruct the trajectory in real time and render it for the broadcasters. They are also the people who created the virtual yellow first-down marker used in television broadcasts of football games. The Chief Technology Officer of Sportvision is Marv White, an alumnus of the University of Illinois Department of Physics.
How to download: A description of the procedures for downloading pitchtracking data and of the meaning of the various quantities in the file.
Pitch tracking technology: A brief discussion of the technology similar to that used by Sportvision PITCHf/x system for tracking pitches in realtime.
Effect of the Magnus Force in the PITCHf/x Tracking System (new December 19, 2007): How to use the PITCHf/x data to get improved values for the break of the pitch due to the spin of the ball.
A Statistical Study of PITCHf/x Pitched Baseball Trajectories (new February 2, 2008): A statistical study addressing the overall accuracy of the PITCHf/x parametrization of the trajectories and the effect of random measurement error on derived quantities, such as the break of the pitch.
Determining the Drag Coefficient from PITCHf/x Data (new March 7, 2008): This short paper, co-authored with Ike Hall, discusses the importance of getting the drag coefficient and shows how to extract it from the PITCHf/x data. It is also shown how to extract the lift coefficient and spin axis. See also Ike's Baseball Blog.
A PITCHf/x Primer by Mike Fast. Note particularly the link to Mike's earlier post about how to write a PERL script to build a MySQL database of PITCHf/x data. Such techniques are extremely powerful, although not for the faint-of-heart. For information on how to link PITCHf/x data to Retrosheet, see the nice article by Dan Turkenkopf.
Catalog of analyses posted on the web of PITCHf/x pitch logs, as compiled by The Hardball Times and updated regularly. This is your "one-stop shopping" site for some very nice articles. See also the excellent Pitch Classification Tutorial by John Walsh, Web-Based PITCHf/x Tool by Josh Kalk, and the very nice work of Mike Fast.
My own analysis (updated Nov. 27, 2007) of pitches in which I give a "physics" analysis in terms of drag and lift as well as a scheme for classifying pitch types. All the relevant formulas are given in this analysis.
Batted Ball Analysis: (link added February 13, 2008) An analysis I did using PITCHf/x video to analyze the initial part of a trajectory of a batted ball.
A first look at 2008 PITCHf/x data: (new April 10, 2008) An analysis by Josh Kalk dated April 1, 2008.
PITCHf/x Wiki (new April 21, 2008) An excellent wiki put together by Dan Brooks at the Sons of Sam Horn site, the best Red Sox blogger site out there! See also Dan's PITCHf/x Tool.
First Annual PITCHf/x Summit. A gathering that took place May 10-11 in San Francisco.
What Are We Learning from PITCHf/x
Powerpoint slides of a talk I gave at SABR38, the annual meeting of the Society of American Baseball Research,
Cleveland, June 27, 2008. After the talk, Cory Schwartz of MLBAM did an on-camera interview with me, which can be viewed at here.