Tracker is Awesome.

I have written before about the importance of measurement, and the importance of authenticity. Of course, these beg the question of how one can produce accurate measurements of real-life events in order to analyze them.

I have used probeware – I still have five sets of probes (with awkward serial interfaces) in my classroom, but I rarely use them anymore, at least for any experiments involving motion. Probes have the advantage that they provide immediate graphical representation of events, but they don’t require the thinking that goes on with measurement.

These days, my tool of choice is Tracker, created by Douglas Brown, a retired Physics instructor at Cabrillo College in California. Tracker, as its name suggests, is video analysis software. But it is much more: it can model dynamic systems and superimpose these models on a video, it can plot vectors, track rotation as well as x and y displacement, track objects in a moving frame (ie for hand-held or panning videos), it can track intensity changes in space and time to get brightness curves, and it can export individual frames from a video. It also has a built-in, comprehensive set of graphing and analysis tools, or the data can be exported to a spreadsheet. And here’s the best part: tracker is free (under GPL), and multi-platform. In short, Tracker is my new BFL (Best Friend in the Laboratory).

Only a few short years ago, video analysis software was costly – at least for a site license – and it was awkward to capture and download video. Now, most students have a phone or iPod that will capture video that can be downloaded and analyzed immediately. Which means students can set up an experiment, video it, and analyze it immediately.

Tracker will track a point automatically if it is sufficiently high contrast, otherwise one must track the points manually – which has the advantage of having to decide exactly which points to track, how many frames per data point, and a variety of other variables that require thinking and experimenting. It thus provides a free, easy to use, rich analysis tool that still requires critical thinking and student involvement. You can see why I like it so much!

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