Drift plot

This page shows a drift plot for the roll listed above. The next plot shows the left-to-right drift of the roll throughout the scan. The axis units are in pixels, with the image scanned at 300 dpi. So the total range of the plot represents about 0.2 inches, or 5 mm. The horizontal axis if the plot is the position in feet from the first musical hole on the roll (drift is not analyze before or after the music).

The following plot (in red) shows the slope of the drift plot. The slope is taken as the difference between the current position on the roll and the position one inch (300 pixels) later. This value is then smoothed to remove irregularities caused by small-scale deviations.

The third plot in green shows the acceleration, which is the slope of the slope of the drift plot. This plot is also smoothed to remove small-scale features.