POST 47:MEASUREMENT

What is Tracker?

Tracker is a free video analysis and modelling tool built on the Open Source Physics (OSP) Java framework. It is designed to be used in physics education.

Within this research proposal Tracker will be adapted to analyse velocity, height and duration of vertical jumps.

Tracker video modelling enables computer modelling of videos.

I have previously used tracker to count the heart beats of Drosophila and to measure the velocity and trajectory of a leap.

JUMP.png

Tracker relies on identification of subjects mass. In my protocol this is recorded to measure BMI.

A fixed height or length in the room allows me to pre-programme a scale which will be used to identify height from he video.

The centre of the mass is then stored on the computer.

A track of the points covered during the leap are recorded and this data used to form the graph.

Boys were particularly interested in the software and were eager to better their jump height and receive feedback to improve their technique. Girls were more anxious that others did not see their mark.

Conclusion:

Using the Tracker programme, I was able to calculate the height, acceleration and velocity of the leap an number of heart beats of the drosophila.

I have much to learn with the uses of Tracker and the following information from the website has been included as this will direct my practice..

Tracker Features

Tracking:

  • Manual and automated object tracking with position, velocity and acceleration overlays and data.
  • Center of mass tracks.
  • Interactive graphical vectors and vector sums.
  • RGB line profiles at any angle, time-dependent RGB regions.

Modeling:

  • Model Builder creates kinematic and dynamic models of point mass particles and two-body systems.
  • Model overlays are automatically synchronized and scaled to the video for direct visual comparison with the real world.
  • New Data Tracks use data from external models including EjsS simulations.

Video:

  • Free Xuggle video engine plays and records most formats (mov/avi/flv/mp4/wmv etc) on Windows/OSX/Linux.
  • QuickTime video engine also supported on Windows and OSX.
  • Video filters, including brightness/contrast, ghost trails, and deinterlace filters.
  • Perspective filter corrects distortion when objects are photographed at an angle rather than straight-on.
  • Radial distortion filter corrects distortion associated with fisheye lenses.
  • Export Video wizard enables editing and transcoding videos, with or without overlay graphics, using Tracker itself.
  • Video Properties dialog shows video dimensions, path, frame rate, frame count, more.

Data generation and analysis:

  • Fixed or time-varying coordinate system scale, origin and tilt.
  • Multiple calibration options: tape, stick, calibration points and/or offset origin.
  • Switch easily to center of mass and other reference frames.
  • Protractors and tape measures provide easy distance and angle measurements.
  • Circle fitter tool fits circles to 3 or more points.
  • Define custom variables for plotting and analysis.
  • Add editable text columns for comments or manually entered data.
  • Data analysis tool includes powerful automatic and manual curve fitting.
  • Export formatted or raw data to a delimited text file or the clipboard.

Digital Library resources:

  • OSP Digital Library Browser provides easy access to online collections of videos and Tracker resources.
  • Use the DL Browser to find resources by name, author, keywords or other metadata.
  • Use the DL Browser to create, edit and share your own video and resource libraries.
  • Use Tracker to export self-documenting ZIP resources ideal for the DL Browser.

Other:

  • Full undo/redo with multiple steps.
  • Page view displays html instructions or student notes.
  • User preferences: GUI configuration, video engine, default language, font size, more.

Tracker Video Tutorials

These video tutorials can help extend your knowledge of Tracker.

  1. Tracker Quick Start A quick demonstration of how to use Tracker to measure the acceleration of a falling ball. If using Tracker for the first time, watch both this and Getting Started with Tracker.
  2. Getting Started with Tracker A more extended explanation of how to use Tracker to track and analyze a moving object in a video.
  3. Tracker Autotracker Tutorial How to use the autotracker. This starts out with the basics but also explains in detail how the autotracker works and how to control it for best results.
  4. Saving and Sharing Tracker Experiments How to (a) save Tracker experiments by exporting Tracker zip (TRZ) files and (b) share them by building Digital Library Collections.

Sample videos

The Tracker installer includes some videos. Use the following links to download these additional collections:

  1. mechanics_videos.zip (7.3 MB) A collection of mechanics videos suitable for analysis and modeling.
  2. spectroscopy_videos.zip (0.6 MB) A collection of spectroscopy videos suitable for line profile analysis.

Conference Presentations

  1. Sharing Video Experiments with Tracker Digital Libraries (AAPT, Winter 2013 at New Orleans)
  2. Simulating What You See: Combining computer modeling with video analysis (MPTL16 – HSCI 2011, Fall 2011 at Ljubljana)
  3. Video Modeling with Tracker (pdf) and accompanying jar file (AAPT, Summer 2009 at Ann Arbor)
  4. Video Modeling: Combining Dynamic Model Simulations with Traditional Video Analysis (AAPT, Summer 2008 at Edmonton)
  5. Modeling Air Resistance (AAPT, Summer 2007 at Greensboro)
  6. Video Spectroscopy Experiments (AAPT, Summer 2005 at Salt Lake)

I will use the following sources to assist with my use of Tracker:

  1. Particle Model Help
  2. AAPT Summer Meeting posters Video Modeling (2008)
  3. Video Modeling with Tracker (2009)
  4. Direct communication with Dr J McLean, St Matthew’s Academy

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