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The team shoots thousands of precise sequential images of the groove and then stitches the images together, measuring the shape of each undulation and calculating the route a stylus would take along the path.

"We grab the image and let the computer model what the stylus would have done if it had run through the surface," said Carl Haber, a senior scientist at the lab who led the research team in collaboration with Vitaliy Fadeyev, a postdoctoral researcher there.
http://www.boingboing.net/2004/05/06...lps_by_sc.html