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Data Set and Source

Download data set

This data comes from David Hill at Richard Superfine’s laboratory at the University of North Carolina at Chapel Hill. It is data from 2.8-micron beads diffusing in a 2% mucus solution. This is a good test case for tracking because the beads go in and out of focus, and move past stationary objects on the cover slip. The beads do not take large steps between frames, so the follow_jumps control is not required.

Recommended Analysis Procedure

Download the data set using the link above and unzip it.  Start Video Spot Tracker by dragging the file named 1um_and_2p8um_beads_in_2pct_mucus_08.clip.avi with the mouse and dropping it onto the Video Spot Tracker icon on the desktop.

Set the radius slider on the kernel control panel to around 22 (or click on the number under the slider and enter 22) to set the radius of trackers that will be used. Click with the left mouse button on the two beads to put symmetric (default) trackers on them. Click the small_area checkbox if you want to reduce the amount of video data that is updated to be near the beads. Click the optimize check box in the kernel control panel. The tracking window should look something like this:

Click the play_video check box on the lower-left control panel. The trackers should follow the two beads as they move in the image and the green outline should follow the set of tracked beads.

This particular video was chosen because it is a good test of the capabilities of the spot tracker program. As the beads go in and out of focus, they change from bright-centered to dark-centered and also become clearer and blurrier. The symmetric tracker was developed to handle exactly this case, where the objects being tracked are circularly symmetric but otherwise vary dramatically during tracking. Also, the beads pass under non-moving small blemishes in the image caused by specks on the imager or on the lenses; the large symmetric kernels do not respond to such features unless they are correlated with the circular symmetry of the particles being tracked.