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Interested in Video Analysis - Printable Version

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RE: Interested in Video Analysis - JSMills - 01-01-2020

(01-01-2020, 11:31 AM)Sebastian Staacks Wrote: Well, the plan is to look into the camera 2020. Not yet sure what's possible.

Thanks for the quick reply. I truly appreciate your work. Even if your app is left as-is, it is a great tool for students to use.

Let me quickly expound on the use of video analysis in the Physics classroom with what I have discovered over the last two years of hodgepodge-y use:
  • Students love to use their phones over other devices, including Chromebooks and data-loggers like the LabQuest 2.
  • Video Analysis of objects in motion greatly enhances students' understanding of physical principles.
Some simplistic examples I have used the past two years:
  • Even at the most fundamental levels of kinematics and projectile motion, students physically tapping the path of a ball under free fall, frame by frame, and then seeing gravity's indelible effect of increasing how far the ball has dropped over each equal time period becomes a stunning effect.
  • Plotting the paths of n ball dropped as an identical one is shot horizontally, the students can see, frame by frame, the equal heights of both. The parabolic trajectory shown is a great lead-in to the position formula in kinematics.
  • Students that are able to analyze this themselves triggers some switch in the mind to accept these wonderful but basic physical principles.
  • There is no inexpensive and convenient way to currently use phones for this. Android has one decent app currently: VidAnalysis. It works, but not as well as it should. I personally bought the paid version to support their efforts, and I had two groups use the free version with acceptable results.
  • Most students have iPhones. I was unable to find an inexpensive app at all. I don't own one, but students graciously left me their phones so I could experiment during my planning time.
  • I briefly entertained the idea of purchasing the app myself for the 4 groups that didn't have Androids, but it was $5.99 I believe. And since it would be linked to their phones, I'd obviously "lose" access to these apps once the semester ended.
  • As a teacher, I found that using disparate systems for each group invited chaos--steps and even terms that applied to an app on one device did not apply to the other, sowing confusion.
  • Ultimately I used an offshoot-version of the Tracker software on our class Chromebooks--jsTracker I think it was called.  It ran well fairly well but still involved more steps than I would like for early principles.
  • However, I put many, many hours into trying to find a solution that was affordable (I bought 6 usb drives to use for this) and fairly seamless for the students. Because,...
  • ...Lastly, I have found that if the apparatus/equipment used in discovery labs are too onerous, then early physics students associate that complexity with the principles themselves. This undermines the entire idea behind the usage of video analysis.
The result of this pilgrimage of mine: I will start looking anew when I teach physics again next year, hoping there is a better solution.

Again, I appreciate the app you have now and the obvious love and respect you have for empowering students in their physics endeavors. Both my students and myself thank you for this wonderful software.

J. Mills

RE: Interested in Video Analysis - crackwitz - 06-28-2020

in case you need more encouragement to add basic camera support (brightness):

cameras can see IR. many wattmeters today emit an IR pulse every 1 Wh or so (1 kWh / ~1000..10000 Pulses). to read that, you just need to press the phone's camera right on top of that LED, sum/average the whole picture to get a brightness reading, plot over time, do some simple thresholding, and calculate (1 kWh / pulse count / time difference) to get current power. since camera data has poor time resolution (1/30 sec usually), this is a good way to show what lowpass filtering can achieve.

if you're driving on a road with "Leitpfosten" (retroreflectors every 50 meters), you can pick those up too, and calculate traveled distance and speed. just point the phone out the window, zoom in, and turn on its flashlight to make use of the retroreflectors.

another simple measurement would be taking one scanline (horizontal or vertical) out of the picture. you can plot that over time like a waterfall diagram. you can also find the maximum and plot that.